Valley of the Mastodons – Part 1

There is a certain quiet at that altitude.  A height where the normal cacophony of daily life—human and otherwise—fades into the wind; where the senses of sight and smell take over; where it is easy, in that relative silence, to contemplate the eons that have come and gone, and what those eons have left in their wake.

Image of Diamond Valley Lake, taken by Jeanne Timmons

 

We were not in the Alps, but we were at a considerable height, surrounded on all sides by a dearth of civilization. The only beings making any kind of noise atop the viewing point for Diamond Valley Lake were those in our small group: a handful of paleontologists, a geologist, an archaeologist, the museum’s PR person, a poet, a paleoartist and a couple of writers.  It was why we’d all come from various places in North America to Hemet, California.

Not for the lake, of course.  But what had been found deep beneath it, before the lake had even come into existence.

Its origins took shape over two decades ago, when a site was needed to create a 6-month emergency water supply for southern California.  It had to be enormous, it had to be situated on relatively stable land geologically, and it had to be able–when needed–to provide that water by gravity.  The neighboring Diamond and Domenigoni Valleys met that criteria.

We were looking over this vast expanse of water, knowing full well that through the 1990s, this was where paleontologists Kathleen Springer and Eric Scott excavated for 7 years.  They and their team of volunteers worked six days a week, 20 hours a day in separate shifts, finding 2646 fossil localities that produced 100,000 fossils.

I thought a lot about the depths those fossils lay, the tonnage of rock and sediment above them, sheltering them from the surface climate, the thousands of years of changes.  How—if senses had been a part of their experience—they might have eventually felt the weight of truly enormous construction vehicles slashing into the very rock that protected them. How, in time, a softer, much gentler movement may have shifted the rock and dirt—the work of an army of humans eager to find them. Until at last, rays of light—warmth unfelt for an unfathomable amount of time—revealed their existence.

It must have been incredible, finding the first set of fossils.  How must it have felt to consistently find more and more and more? I wondered, too, about Kathleen’s personal experiences, especially as she knew the fossils would not only be there, but that they would be profuse. 

But we arrived at a different point in the story, long after the initial discovery. The fossils had been long since been collected, cleaned, and labeled. They were now housed at the Western Science Center in Hemet, not far from Diamond Valley Lake.  And we’d come to study them, discuss them, learn from both the fossils and each other, and share that knowledge with the public.

It was a unique idea, the “Valley of the Mastodons” workshop and exhibit.  Dr. Alton Dooley, jr.—Executive Director of the Western Science Center—and Dr. Katy Smith—Associate Professor at Georgia Southern University—invited paleontologists who had studied various aspects of mastodon anatomy to research the mastodons within this largely unstudied fossil assemblage.  But they also invited some of us outside the field: an artist, a poet, a couple of writers.   After a series of days, loosely structured to allow for research and outreach, an exhibit of mastodon fossils would be unveiled to the public.

All of it was new to me; I’d never attended a scientific conference before.  But I had seen the schedules of larger events—days filled with presentation after presentation, exciting scientific research explained to those lucky enough to attend them.  Even with my limited knowledge of such things, however, I recognized this for what it was: an innovative experiment.

How was this different than other scientific conferences?

Size, for one.  Rather than thousands of participants, there were less than 20 of us actively involved.

Audience, for another.  This was not a forum created solely for scientists to speak with other scientists. The larger goal, and one that was woven naturally into each day, was bringing that research to the public. Inviting them in, encouraging questions, sharing what was being learned right there on the museum floor as the research was being done.

And structure. The structure of those days, as mentioned previously, was far from rigid.  Aside from a morning of presentations, where scheduling became important, most days were fairly open—enabling all of us to do what we needed or wanted to do as we felt best to do it.  From my vantage point, it felt like Alton and Katy opened the doors to the museum, pointed to the fossils and said, “Make yourself at home.”  Which is exactly what everyone did! And it’s amazing how fast days go by when you are doing something you love, something about which you are passionate and enthused, surrounded by those who feel the same way.

The first day I felt almost dizzy, watching everything and everyone around me, excited to witness it, excited to participate, if a little unsure how best to move forward.  It was not a question of my ability to engage and then write about it; my uncertainty was determining where to focus, who to observe, what—of all the myriad things taking place around me—to be part of.  There was so much going on all at once!

As an example:

• Katy measured tusks;
• Dr. Jeremy Green (Kent State) sampled tusks;
• Greg Smith (PhD candidate at Vanderbilt) and Dr. Grant Zazula (Yukon, Canada) studied mastodon molars Grant had brought with him;
• Dr. Bernard Means (VA Commonwealth University) scanned smaller fossils for 3D images online;
• Dr. Chris Widga (East Tennessee State University, Gray Fossil Site) scanned larger fossils for that same purpose;
• and others helped move fossils from their displays or the collection for research.

 

Dr. Katy Smith measuring mastodon fossils, photo by Jeanne Timmons

Paleos (and a writer and poet!) at work, photo by Jeanne Timmons

Members of the public congregated near them, some asking questions, many others observing quietly.  The jocularity of some of the paleontologists broke that barrier, changing visitor observation to interaction. I was a bit star-struck myself by these paleontologists. I marveled at their casual charisma, their down-to-earth conversations, their ability to engage people of all ages.

 

Greg Smith and Dr. Grant Zazula working on mastodon molars from the Yukon, photo by Jeanne Timmons

Public observation on the museum floor, photo by Jeanne Timmons

 

Even on breaks, when we stopped for lunch or dinner or any other reason, there were constant discussions about proboscidean research or paleontology in general.   Some of us discussed books we’d read or were reading; others spoke of current research.  With almost unquenchable thirst, I drank it all in–from the most serious to the most frivolous of moments–whether I was part of the conversation or not.  These moments were what I’d dreamed of: seeing paleontologists in action.  I LOVED it.  But taking in everything and feeling such an intense emotional high takes its toll.  By the end of each day, my head reeling with information and experiences, I was more than ready to retire to my own cabin, my own space, my own quiet.

 

 

 

 

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North American Proboscideans and Dr. Chris Widga – Part 1

“Most zooarchaeologists are interested in the people, and they use the animals as kind of a tool for understanding butchering patterns or food ways or something like that.”

Dr. Chris Widga and I were in the midst of a great conversation about three recent papers he co-authored, paleontology, proboscideans, and the state of science today.

“I was always interested in the animals themselves,” he continued, “so when I got the position as a vertebrate paleontologist at the [Illinois State Museum], all of my friends who’d known me for years said, ‘well, that was a no-brainer for us. You were doing vertebrate paleontology all the time on Holocene bison. You never cared much about the people!’”

That beginning in zooarchaeology and the subsequent immersion in paleontology are what give him a unique perspective of the two sciences.  Or, as he himself explained: “I guess I kind of have this foot in both worlds.”

The two occasionally overlap.  In the paper published this past February in Boreas, “Late Pleistocene proboscidean population dynamics in the North American Midcontinent,” he and his colleagues take a closer look at what might have caused the extinction of mammoths and mastodons in what is now the middle of North America. Possible culprits include climate change, shifts in available vegetation, and predators (including humans).

Of the 627 localities included in this study, only 3 offer any kind of human association.  The authors state that these sites were “re-visited to ensure consistent taphonomic and zooarchaeological data,” and that, despite this, whether or not these specific humans and proboscideans interacted remains unclear.

“That’s a distinction I like to make as a paleontologist and a zooarchaeologist,” Dr. Widga offered. “Just because we have a couple of the sites with humans associated [doesn’t necessarily indicate that] humans actually hunted, killed and butchered those animals.  [Humans] may have scavenged them.  They may just simply be associated in these sites. And very few of those sites have been analyzed to the degree of detail that we really need to start teasing apart those issues.”

What he and co-authors Stacey N. Lengyel, Jeff Saunders, Gregory Hodgins, J. Douglas Walker, and Alan D. Wanamaker try to do, however, is take a deeper look at the late Pleistocene environment in which these proboscideans lived.  It’s exciting research: Rather than simply describing fossils discovered in the various US states and one Canadian province, they are trying to put them into context.  In other words, they are trying to understand the ecology of that time period and how that may have affected the megafauna living within it.

But it’s not an easy task.

“Ecologists can look at modern ecosystems and say, ‘Ok. This is what’s going on, and this is why we think that, and this is how we’re measuring it’ in great detail.  But extrapolating those same processes back into the paleontological record is often really, really difficult even with the best data set.

For example, “[w]e can observe boom-and-bust cycles in deer populations, in caribou populations, in musk ox and things like that. But when you try and translate that into the paleontological record, most of the time it’s really difficult because you simply don’t have the samples and you don’t have the time resolution.

“Even in our case, where we have really good samples and we have really good dates on our samples and we’re creating this chronological structure to kind of fit them in, it’s really difficult to translate those patterns into ecology.

“We can’t date a single mastodon any more precisely than about a hundred-year window.”

The fact that some of the ecological constructs used today in extant populations are controversial makes trying to apply such constructs to extinct animals that much more of a challenge.

“When even the ecologists can’t truly [agree upon] what’s going on, you have to navigate things very, very carefully.”

The amount of work put into this paper (work that has produced previous, subsequent and yet-to-be-published papers) is staggering.  Thanks to a National Science Foundation grant, Dr. Widga and Dr. Jeff Saunders—both previously at the Illinois State Museum—were able to visit an astounding number of museum collections in the Midwest and review their proboscidean fossils.

“We’ve [basically] spent the last 5 years in other people’s collections,” he explained. “It was fun because we visited a lot of collections that people don’t usually go to. About half of the data set comes from repositories that have fewer than five mammoths and mastodons.”

 

 

An inside look at the extensive fossil collection at the Indiana State Museum collection–one of the many collections visited by Dr. Widga.  In our conversation, he said, “The Indiana State Museum is a big dot on the map in terms of mammoths and mastodons, in part because of [paleobiologist Ron Richards’] work!”   This image was taken in 2005, picturing then Collections Manager Michele Gretna (currently Director of Archaeology); image courtesy Indiana State Museum and Historic Sites.

Another inside look at the Indiana State Museum collection; Preparator Elizabeth Scott after the reconstruction of the Kolarik locality mastodon tusks, 2014; image courtesy Indiana State Museum and Historic Sites

 

 

Their work involved the review of over 1600 fossils that currently reside in collections in Ontario, Canada, as well as in Arkansas, Illinois, Indiana, Iowa, Kansas, Kentucky, Minnesota, Michigan, Nevada, Ohio, South Dakota and Wisconsin.

“We doubled the number of known published sites for mammoths and mastodons in the Midwest.”

Information that they are willing to share with other scientists, as evidenced by the number of papers they continue to co-author.  Following the Boreas paper, Dr. Widga was part of another two papers published in March in Quaternary International and then in Scientific Reports.

Mammoth teeth take a leading role in the paper, “Reconciling phylogenetic and morphological trends in North American Mammuthus,” published in Quaternary International and co-written with Jeff Saunders and Jacob Enk.

“We’re starting to put out some of these ideas that actually put data onto these [traditional] species boxes that we like to put specimens into.  So that was one of the first steps into thinking about these things: more as morphologically variable populations rather than just trying to assign them to a particular species.

“A lot of times these studies kind of happen in isolation.  So the people that think about morphology, they’ll publish on the morphology and then post-hoc, they’ll say, ‘oh but this doesn’t agree with the genetics at all.’ Or the geneticists will publish on the genetics, but they don’t integrate any morphology.  So our point was to try and integrate both of them and see what they say. Can you use the genetics to kind of structure your interpretations of what the morphology means?”

The authors studied “M3s”—the permanent upper 3^rd molar—of both female and male mammoths of various ages from museum collections and from previously published work.

Per Dr. Widga, this is the upper 3rd mammoth molar from Clear Lake Sand and Gravel Pit, Sangamon County, IL. One of his favorites from the ISM collection. It dates to the Last Glacial Maximum and had preserved DNA so is included in the Enk dataset; image and caption courtesy Chris Widga.

 

“Jeff [Saunders] and I would say, ‘this genetic information actually fits perfectly with our morphological information which suggests that there’s a lot of population overlap in between these normally well-defined populations.’ So in between Columbian mammoths in the Great Plains and woolly mammoths from the Great Lakes you have Iowa mammoths that show characteristics of both. And also they show characteristics of both in the same animal!

“That was kind of the impetus for the [Quaternary International paper]: to get that out there, show that you do get a lot of overlap in the morphology. It’s not just clean boxes of Columbian mammoths and woolly mammoths. And even pygmy mammoths overlap with Western Columbian mammoths! So that was kind of the point of the paper: to get the conversation going and make a first pass–a first attempt–to reconcile the two data sets.”

Following soon after the paper in Quaternary International, he was part of a remarkable group of proboscidean and genetic scientists whose paper The evolutionary and phylogeographic history of woolly mammoths: a comprehensive mitogenomic analysis analyzed 143 woolly mammoth mitochondrial genomes.

As Dr. Widga said with characteristic enthusiasm about his work in paleontology, “It’s always fun! There’s always a mountain to climb and a vista to see!”

*****

A Mammuthus columbi-sized THANK YOU to Dr. Chris Widga, who was remarkably generous with his time, with images to use and with answering my many, many questions (both for this blog and for my own proboscidean curiosity).  Speaking with him was delightful; he is an incredible ambassador for science in general!

Another sincere THANK YOU to Ron Richards for providing the great images of the Indiana State Museum collection. 

References:

1. Widga, C., Lengyel, S. N., Saunders, J., Hodgins, G., Walker, J. D. & Wanamaker, A. D.: Late Pleistocene proboscidean population dynamics in the North American Midcontinent. Boreas. 10.1111/bor.12235. ISSN 0300- 9483.
2. Widga, C., et al., Reconciling phylogenetic and morphological trends in North American Mammuthus, Quaternary International (2017), http://dx.doi.org/10.1016/j.quaint.2017.01.034
3. Chang, D. et al. The evolutionary and phylogeographic history of woolly mammoths: a comprehensive mitogenomic analysis. Sci. Rep. 7, 44585; doi: 10.1038/srep44585 (2017).

Mastodon fossil at the Illinois State Museum; image courtesy of Chris Widga.

Rewriting the Story of How They Died – Columbian Mammoths in Waco

[[The following text has been edited from the original post.  Email me for the original post: mostlymammoths (at) gmail.com or read the full scientific paper by the authors here.]]

*****

Sometimes, it just takes a different point of view.

The largest known potential nursery herd of Columbian mammoth fossils in the world exists in Waco, Texas.  Of the 25 mammoth skeletons found to-date, 16-22 of them died at the same time. Something catastrophic occurred to these animals in the Pleistocene, but just what remains inconclusive.

While some speculate death by lightning, disease or miring, the predominant theory maintains that this is a herd of mammoths that died and were buried in the same flash flood.  It’s an idea that has stuck for many years given the existence of aquatic fauna and the evidence of an ancient river upon which many of the fossils have been found.

Image of Female Mammoth “W” at the Waco Mammoth National Monument, photo by Larry D. Moore CC BY-SA 3.0, 2013

 

But Logan Wiest, Don Esker and Steven Driese of Baylor University have a different hypothesis, one published this past December in Palaios.  By studying traces on the bones available in situ, as well as those available in the nearby Mayborn Museum, they offer an entirely new idea: water didn’t kill them; its absence did.  Struggling to find water in a drought, these animals may have collapsed and died at a watering hole that could no longer sustain them or anything else.

Columbian mammoths were enormous animals.  In general, they are known to be much larger than woolly mammoths and considerably larger than mastodons, both of which were behemoths in their own right.

The mammoth skeletons at Waco are thought to be a matriarchal herd, consisting mainly of females and youth (no calves).  The evidence suggests a herd, and there is more research to be done to prove it using stable isotopes.  A single bull has been discovered in a different geologic layer.  Separate fossils of other species—none of them complete except for a western camel—have also been found throughout the site.

Don admitted he didn’t have an alternative explanation for the death of so many animals. He invited his colleague, Logan Wiest, to take a closer look at the fossil evidence.

“I’d brought [Logan] in hoping he’d look at the [site’s paleosols],” Don said. “I knew he was a trace fossil expert, so I’d hoped he [might] tell me a little bit about the conditions based on worm burrows, [for example].

“What he found instead was much more interesting! He found that there were all kinds of bite marks on the bones.  We didn’t find those all at once.  It actually took quite a while [before] we recognized what we were seeing as bite marks.  A lot of literature research and a lot of staring at bones.  Those bite marks shouldn’t have been there if the mammoths were immediately buried.

“One of the first things he noticed and was able to identify quickly were dermestid beetle bite marks: pits that the beetles dig in the bones when they’re going to lay eggs.

“I thought that perhaps [evidence of dermestid beetles] might be there, but I didn’t realize the significance of [that evidence].  He’s more of an expert on this than I am.

“And he knew that dermestid beetles don’t eat wet meat.  It actually has to be almost completely dessicated–no moisture left at all, just the fats and proteins–before the dermestid beetles will touch it. And that didn’t fit well with animals that were killed in a flood and rapidly buried.

“Dermestid beetles also don’t burrow. Even a single inch of soil is enough to keep dermestid beetles from digging down to perfectly good meat.  They can’t dig.”

FIG. 7.—Cubiculum isp. on various skeletal elements. A) Slightly elliptical, hemispherical bore on in situ rib of mammoth W. B) Hemispherical boring on mammoth U phalanx (545-BU-MMC). C) Shallow bore on femoral articulation surface 761a-BU-MMC. D) Shallow bore on eroded long bone of mammoth D limb fragment (203-BU-MMC). E) Hemispherical bore in cancellous bone on the surface of a spiral fracture (20-BU-MMC). F) Comparative trace generated by captive hide beetles on a wild-hog skull (Sus scrofa). Note the similarities in size and morphology to Figs. 7A-E.

 

Used with permission, PALAIOS, v. 31, 2016, doi:10.2110/palo.2016.053, © SEPM Society for Sedimentary Geology 2016.

 

“So, it was Logan looking at this and trying to think about what might be causing this instead of a flood, and he said, ‘Well, how about a drought?’

“I knew about some other evidence that really fit with that. So that clicked with me very quickly, particularly the fact that we’ve got both aquatic and terrestrial animals—a great diversity of them all in the same place.  What that suggested to me was a diminishing watering hole. And I wouldn’t have realized that if Logan hadn’t noticed the dermestids and figured out the drought angle.”

Beyond studying the available literature for trace fossil search images, they tested their ideas on the heads of deceased wild hogs using extant dermestid beetles. In effect: they put the fleshy heads into a contained area and let loose the beetles, who proceeded to consume all of the flesh, leaving clean skulls. It’s an efficient and chemical-free method used by scientists and museums the world over.  But for Logan, Dan and Steven, this provided more data for comparison. Traces left by the beetles on the wild hog skulls are similar to traces on the fossils in Waco.

 

Screenshot of a tweet regarding the use of dermestid beetles from Dr. Lisa Buckley, paleontologist and ichnologist at the Peace Region Palaeontology Research Centre

 

“Previous studies have attributed trace fossils of this size and morphology to dermestid beetles,” Logan wrote in response to what prompted them–of all insects that might have left traces on fossils–to think of dermestid beetles.  “We simply wanted to test this notion by providing bone to dermestid beetles and seeing if these traces could be duplicated under controlled conditions. The beetles came from a nearby museum, but they are also native to Texas. We used the head from a hog simply because wild hogs are easily accessible in central Texas.”

A true ichnologist, Logan added, “I’ve also spent a great deal of time observing bones of modern cattle that were scavenged upon in pastures near my home.”

They didn’t just find evidence of ancient dermestid beetle traces; they found traces of animals who gnawed at the bones: rodents and carnivores, including a possible saber-toothed cat.  It is important to consider that animals drowned and then rapidly buried in a flash flood would not be accessible to these terrestrial scavengers.  This indicates that these Columbian mammoth carcasses were exposed on land long enough to be at least partially devoured.

That, too, is key. Remember that most of these mammoth fossils are articulated skeletons, complete except for missing tails and parts of their feet.  In an area devastated by drought, even scavengers would lack the energy to completely devour and tear apart a carcass.  All of these clues add more weight to the scenario proposed by these authors.

FIG. 5.—Brutalichnus brutalis on M. columbi skeletal elements. A) Arcuate grooves on femoral head 761a-BU-MMC. B) Relatively deep, arcuate grooves on mammoth Q in situ patella. C) Isolated arcuate groove on proximal radius (40-BU-MMC) of mammoth B. Note the similarity in curvature between the arcuate groove and the saber-toothed cat canine recovered from WMNM. The tooth is 6.4 cm for scale. Also note the faintly colored lines that are parallel to the arc of the groove. Dashed white box highlights the area depicted in D. D) Close-up image of groove depicting the microfractures within the trace on 40-BU-MMC. Notice how the fractures are all open towards the upper-right corner of the image, indicating the trace was generated from a force moving from the upper right towards the lower left. E) In situ femur of bull mammoth at WMNM. F) Arcuate grooves on mammoth Q phalanx 522-BU-MMC.

 

Used with permission, PALAIOS, v. 31, 2016, doi:10.2110/palo.2016.053, © SEPM Society for Sedimentary Geology 2016.

 

Describing the tools they used to study the fossils in situ, Logan wrote, “The low-angle light creates a shadow which makes the small structures on the bone surface to be easier to see and photograph. We used a Dino-Lite portable microscope to study the fossils mainly because we are unable to transport the mammoth remains from the site to the laboratory. Studying the fossils in place is the best way to ensure preservation of the original positions.”

In other words, because the fossils remain where they were found, they studied those available directly at the site.  Their paper states that the in situ fossils comprise 30% of the available Waco fossils.  The rest reside at the Mayborn Museum, some of which are available in their collections, but most of which remain unopened in their plaster jackets.

“It’s an amazing site,” Don enthused, “and there’s decades and decades of research there, on top of potentially a lot more excavation, too, because they are in NO WAY finished excavating. What they’ve got probably represents a fairly small fraction of the whole deposit.

“One of the things that Logan and I were speculating about [is] if you’ve got a really big regional drought, that should show up in multiple places in the geologic record, especially right in that area.  The bed that we’ve got marking the drought as this depositional hiatus could be covered with bones for acres and acres in every direction.

“And we know that it’s covered in bones at least 80 or 90 feet away from where the known deposits are because we’ve done core sampling that have pulled out large bone fragments.  We only did a couple of them—a couple at random!—and they hit bones both times.”

 

FIG. 4.—Machichnus regularis on various skeletal remains of M. columbi (unless otherwise noted). A) Rodent gnaw marks on rib 764b-BU-MMC. B) Rodent traces on mammoth E limb fragment 203a-BU-MMC. C) Rasps on vertebra of in situ camel. D) Rodent gnaw marks on in situ neural spine of juvenile mammoth T in L1. E) Rodent traces on in situ left scapula of bull mammoth (Q) in L2. F) Close-up image of the same trace depicted in view E.

 

Used with permission, PALAIOS, v. 31, 2016, doi:10.2110/palo.2016.053, © SEPM Society for Sedimentary Geology 2016.

 

 

The Waco Mammoth site itself has been around for 39 years, but it has only been part of the National Park Service since July 2015, thanks to President Barack Obama and the work of many people years beforehand who helped bring that to fruition.  Don and I discussed this by phone, given the current political climate and the fears that some National Monuments might lose their status.

“That’s really worrisome,” he remarked. “And what really sticks in my craw about the Waco Monument in particular is that it’s costing the Federal Government almost nothing.  The city of Waco is paying for almost all of the upkeep.  The original buildings? That wasn’t tax money. That was done by good old fashioned fund-raising. And the day-to-day operations are almost all city.  There are a couple of rangers there alongside city employees and some signage and brochures. And that’s really all the Federal Government’s paying into it.”

“It’s a really incredible place.  There are not a lot of sites like this anywhere, as far as in situ fossils sites go.”

*****

A Mammuthus columbi-sized THANK YOU to Don Esker and Logan Wiest for their remarkable generosity in answering my questions and for sharing their research with me.  It was an enormous pleasure speaking with and communicating through email with them.  I loved reading their research and hearing more of the history behind it!!

You can read the paper here.

A sincere and enthusiastic thank you to Kathleen Huber, Managing Editor at Palaios, for her gracious permission to use the figures contained in this post!

References:

1. The Waco National Monument may represent a diminished watering-hole scenario based on preliminary evidence of post-mortem scavenging, Wiest, Logan A.; Esker, Don; Driese, Steven G., Palaios, December 2016, DOI: 10.2110/palo.2016.053
2. Waco National Monument, Waco, TX
3. City of Waco, TX – Waco Mammoth National Monument, Waco, TX
4. Mammoth Opportunity, Jeff Hampton, Baylor Arts & Sciences Magazine, Fall 2016
5. What is Ichnology? from Introduction to Ichnology, Anthony J. Martin, Emory University (This page offers a great explanation of some of the more technical ichnological terms included in the scientific paper referenced for this post. I also recommend Dr. Martin’s book, “Dinosaurs Without Bones” for a more comprehensive look into ichnology.)
6. Flesh-Eating Beetles Explained, Mollie Bloudoff-Indelicato, National Geographic, January 17, 2013

 

Screenshot of the entrance to Waco Mammoth National Monument from a video done by the City of Waco

Minute Trace Fossils Offer Major Implications For Extinction Recovery

Large body fossils of extinct creatures capture our imagination.  It’s understandable.  These were fascinating behemoths, and we can see something of their life in the bones that remain. While our collective attention might be focused on these very big things, researchers published a paper this past November that centered on some very tiny things.  And what they found has enormous implications for our understanding of ancient life.

Insect feeding damage on a fossil leaf, including holes and a leaf mine (bottom right), made by a larval insect that fed on tissue within the leaf. The fossil is 67-66 million years old and from the Lefipán Formation in Patagonia, Argentina; photo and caption courtesy of Michael Donovan.

 

The authors Michael Donovan, Ari Iglesias, Peter Wilf, Conrad Labandeira, and N. Rubén Cúneo studied trace fossils of insect feeding damage on over 3000 fossil leaves from Patagonia (an area that encompasses the southern part of Argentina and Chile).

Remarkably, fossil leaves number in the tens of thousands in the Western Hemisphere alone.  But studying them for insect damage during the end Cretaceous and early Paleocene is relatively new.  Keep in mind that the end Cretaceous marked the last mass extinction this planet has known thus far.  The early Paleocene marks the time when life was, however slowly, working its way back into existence.

There is a preponderance of fossil leaves in the western interior North America (WINA) from this time period, and they have been studied.  In “Rapid recovery of Patagonian plant-insect associations after the end-Cretaceous extinction” published in Nature Ecology and Evolution, the authors compared the relatively smaller number of fossil leaves in Patagonia to the much larger numbers of such leaves from WINA.

What interested them was the diversity of insect damage to these Patagonian plant leaves.

Tiny insect piercing and sucking marks on a fossil leaf from the fossil locality Palacio de los Loros 2 in Patagonia, Argentina (approximately 64 million years old). Piercing and sucking damage is made by insects that use their straw-like mouthparts to feed on fluids from within plants; photo and caption courtesy of Michael Donovan.

Close up of the picture above; photo and caption courtesy of Michael Donovan.

The type of insect damage—the different ways insects fed upon a leaf–relates to the diversity of insects. That diversity of herbivorous insects, in turn, relates to a much larger food web.  In other words, the traces these ancient insects made indicate that there was a growing population of different types of insects. That growing population suggests a growing, thriving food web.  Life in Patagonia, after the last mass extinction, may have been returning at a much faster rate than its northern counterpart.

Embed from Getty Images

 

“If we’re just looking at the raw numbers, there are way more fossils, but less insect-damage diversity,” explained Michael Donovan in a phone interview referring to the WINA fossil leaf damage.  “In the Western US, there’s around almost 20,000 leaves included in those data sets. Maybe a little less.” He chuckled. “And that’s compared to the 3,646 [fossil leaves] in Patagonia. So, it’s a big difference!”

“We can’t always say exactly what insects were making the damage,” he wrote earlier in an email.  “During this study, we found many different kinds of damage representing the work of a wide range of plant-eating insects. Some types of damage can be made by a variety of insects. For example, many different kinds of insects with chewing mouthparts, such as beetles or grasshoppers, can create holes in leaves by feeding through the plant tissue. Other types of insect damage provide more specific information about the culprit. Leaf mines, for example, are made by larvae of some species of moths, flies, wasps, and beetles. The mines act as a detailed record of the behavior of the insect, which we can use to infer the type of insect that may have made the mine.”

View of an excavation at the Palacio de los Loros 2 fossil plant locality in Chubut, Patagonia, Argentina. The fossils there were formed in the early Paleocene around 64 million years ago;photo and caption courtesy of Michael Donovan.

 

Michael was the one responsible for studying these 3,646 fossil leaves to see if any had any damage to begin with, and then to see whether that damage may have been insect-related.  (In a nod to how I may have organized such things, I wondered whether museum collections separate out fossils with traces of damage.  They do not. Or rather, as Michael explained, “How they are organized usually depends on the collector or museum. The collections used in this study are organized by plant morphotype/species. To collect the data, I inspected all of the leaf fossils under a microscope for insect damage.”)

But how can one determine the difference between disease-related traces and insect-related traces in a fossil leaf?

“One good thing to look for is reaction from the plant to the insect damage,” he answered.  “So, for example, if an insect chews through a leaf and makes a hole, [scar] tissue [will form] around the edges of the hole. On the fossil, it looks like a little dark area surrounding the hole.  That’s where the plant healed itself after the damage was made, and that shows that [the insect ate the leaf] when the plant was still alive. If it happened when the leaf was dead, it wouldn’t form that scar tissue. So if there’s something like a tear that was made when the leaf was already dead, reaction tissue wouldn’t form. Then some other types of damage are very distinctive, such as leaf mines, and look very similar to damage we see on modern leaves.”

Skeletonization (feeding on leaf tissue between leaf veins but leaving the veins intact) caused by a plant-feeding insect. The leaf is from the Palacio de los Loros 2 fossil plant locality in Patagonia, Argentina (approximately 64 million years old); photo and caption courtesy of Michael Donovan.

 

Their research determined that there is a greater diversity of insect-damage to fossil leaves in Patagonia, and that this diversity occurred 4 million years after the meteorite crashed into Earth at Chicxulub, Mexico.  Contrast this to the western interior North America, in which insect-damage indicates that same recovery took 9 million years.

“The fossil plant collections that we studied were collected relatively recently by my coauthors (Ari Iglesias, Peter Wilf, and Rubén Cúneo) and other scientists as part of a larger research program on Patagonian fossil floras from the end of the Cretaceous through the Eocene,” Michael described. “The Paleocene floras have been dated with a variety of methods, which show us that the fossil sites were formed during three time slices in the early Paleocene. Using these dates, we were able to observe how plant-insect associations in Patagonia recovered in the 4 million years after the end-Cretaceous asteroid impact.”

Co-authors Conrad Labandeira and Peter Wilf were part of a 2014 study published in PLOS One (“Insect Leaf-Chewing Damage Tracks Herbivore Richness in Modern and Ancient Forests,” also by Mónica R. Carvalho, Héctor Barrios, Donald M. Windsor, Ellen D. Currano, and Carlos A. Jamarillo) in which extant insect leaf damage was correlated to the larger food web of two tropical rainforests.  The variety of insect traces on today’s leaves represents a healthy variety of insect species.  Like keystone species in any ecosystem, these traces indicate a thriving web of life.

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How remarkable to then extrapolate that insects so many millions of years ago, simply eating the leaves available to them in the Southern Hemisphere, can offer important clues to the state of life after the devastation our planet endured.  The traces of these tiny creatures—and the fragile plants that survived fossilization—are extraordinarily significant.

“It was pretty exciting to see what was happening in another part of the world,” Michael enthused.

When asked why fossil leaves and insects interested him, he responded, “Plants and insects are the most diverse multi-cellular organisms on Earth, and their interactions are important components of food webs on land. By studying insect feeding damage on fossil leaves, we can learn how insects and plants responded to major environmental changes in the past and have a better idea of how they may be affected in the future.”

“This is what I’m interested in continuing doing. This is a relatively newer field within paleontology, so there are lots of projects to pursue, lots of periods of time in the ancient past where we don’t know much about how insects and plants were interacting.”

“The Cretaceous-Paleogene extinction was a major event in the history of life and the most recent of the big mass extinctions. The plants and animals that we see today are all descended from organisms that survived this asteroid impact. We observed a faster recovery of plant-feeding insects in the Southern hemisphere—in Patagonia—compared to the Northern hemisphere—[in WINA.]  These patterns from the early Paleocene may be related to biodiversity patterns that we see today.”

 

Leaf mine made by a larval insect that fed on tissue within the leaf. The fossil is ~65 million years old and from the Palacio de los Loros 1 fossil site in Patagonia, Argentina; photo and caption courtesy of Michael Donovan. 

 

An absolutely ENORMOUS thank you to Michael Donovan for making so much time to answer my questions, both in email and by phone.  The number of pictures he sent, and their detailed captions, was AMAZING.  I did not include them all here. I encourage you to read the paper done by him and his colleagues to see how many and beautiful they are. THANK YOU, MICHAEL!!

 

References:

1. Donovan, M. P., Iglesias, A., Wilf, P., Labandeira, C. C. & Cúneo, N. R. Rapid recovery of Patagonian plant–insect associations a er the end-Cretaceous extinction. Nat. Ecol. Evol. 1, 0012 (2016).
2. Carvalho MR, Wilf P, Barrios H, Windsor DM, Currano ED, Labandeira CC, et al. (2014) Insect Leaf-Chewing Damage Tracks Herbivore Richness in Modern and Ancient Forests. PLoS ONE 9(5): e94950. doi:10.1371/journal.pone.0094950
3. Monocots versus Dicots, University of California Museum of Paleontology
4. Museo Paleontológico Egidio Feruglio, Trelew, Argentina
5. Check out more research done in Patagonia! Patagonia Paleofloras Project

 

Museo Paleontológico Egidio Feruglio, home to the fossil leaves used in this paper and many other exciting fossils; photo by Pedrochubut (Template:MEF Photo) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)%5D, via Wikimedia Commons

Researching Fossil Ungulate Communities

Alces alces (moose), Porkkala, Finland; photo courtesy of Juha Saarinen

In their paper “Patterns of diet and body mass of large ungulates from the Pleistocene of Western Europe, and their relation to vegetation,” published this past September in Palaeontologia Electronica, Juha Saarinen, Jussi Eronen, Mikael Fortelius, Heikki Seppä, and Adrian Lister investigate fossil ungulate communities found in England, Ireland, and Germany.

Not fossil ungulates, fossil ungulate communities.

The variety of fossils studied is just one of the exciting elements of their research.  Rather than focusing on a single species—which, given the limitations of the fossil record, is usually the case—they studied groups of fossils from at least 14 different ungulate species from the Middle to Late Pleistocene.

“[W]e are now at a point,” wrote Juha Saarinen, lead author of the paper, in an email, “where enough fossil material of ungulates and pollen records have accumulated to enable such a large scale quantitative comparison of body size and diets of ungulate with local vegetation patterns in the past as we did. Comparing vegetation proxies and mammal ecometrics from fossil data using such quantitative statistical analyses as we did has, to our knowledge, never been attempted before, so that is probably the most novel achievement of this study.”

The ungainly name of ‘ungulate’ refers to hooved animals: even-toed and odd-toed (Artiodactyla and Perissodactyla, respectively). Examples include horses, deer, moose, rhinoceros, bison, pigs and hippopotamuses.

Brontops tyleri (a type of brontothere and a Perissodactyl) at the Beneski Museum at Amherst College, Massachusetts.   Brontotheres survived until the Eocene, an era that ended approximately 30+ million years BEFORE the Pleistocene, so this animal–although an ungulate–was not part of this study. Picture taken by the author of this blog

 

Using mesowear on the fossil teeth, they were able to determine information about their diets (from browsing to grazing), and by comparing this data with the pollen record associated with the areas in which these fossils were found, they were able to tell whether they ate more browse or grass in either open or closed environments. Body mass for these fossils was calculated and then compared to the diet of these animals.

They were searching for answers to how these species adapted to the environment in which they lived.  How did their body size relate to the vegetation available? Was their body size influenced by possible predators or by other members of their species? (In other words, were they bigger to intimidate predators or were they smaller because they lived in expansive herds?) Or was thermoregulation the single determining factor in how big these animals became, as has been proposed in earlier studies?

 

Megaloceros giganteus (otherwise known as Irish Elk and an Artiodactyl) in between a mastodon and a mammoth fossil at the Beneski Museum at Amherst College, Massachusetts; picture taken by the author of this blog

 

It interested me to learn that they relied on what I rather simplistically referred to as the ‘physical observation’ of fossils.

Mesowear analysis looks at the wear and shape of fossil teeth.  Various plant material affects tooth-wear in distinctly different ways, which can be seen both on the teeth themselves and in the way the teeth have evolved.

To be clear, “this is specifically wear-induced shape, not the original shape of the unworn teeth,” Juha added. “In other words, mesowear is the change in the shape of the teeth as they get worn, and different food items cause different worn shape to develop (browse maintains high and sharp features on the tooth surface, whereas grass “grinds” them down leading to them to progressively wear down lower and more blunted the more there is grass in the diet).”

Examples of a mammoth tooth — used to eat mostly grasses and sedges — and a mastodon tooth — used to eat trees and shrubs. Notice the very different shape of these teeth for very different types of vegetation. Proboscideans such as mammoths and mastodons were once grouped in with ungulates, but this has changed. Picture taken at the Harvard Museum of Natural History by the author of this blog.

 

Obtaining data about the pollen record (non-arboreal pollen percentages, or NAP %) meant researching published information and connecting that information with the related fossil sites.

The mathematical work behind all of this–determining mesowear, animal body size, and then relating this to the available pollen record—is staggering.

Surely, I thought, isotopic analysis would have been a much easier way to obtain information about each fossil’s diet at least.  Especially given that the pollen record isn’t always available, or—in one case—runs the risk of being skewed by the defecation of Pleistocene hippopotamuses that grazed in the area.  Why, I wondered, did they rely on methods that seemed considerably more labor-intensive and potentially (to my understanding) less accurate?

“There are a number of reasons for this,” Juha explained. “First, we wanted to obtain as much palaeodietary data as possible, comprising as complete ungulate communities as possible, and this meant dealing with very large samples of fossil molar teeth. Taking isotope samples from all those teeth would have been laborious, time consuming and expensive, not to mention also slightly destructive to the fossil specimens.

Cervus elaphus (Red Deer, Artiodactyl) at Richmond Park, London; photo courtesy of Juha Saarinen. Red Deer are one of the most extensively studied animals today. You can read about another study that references Red Deer in this post.

 

“Second, stable isotopes work best at resolving herbivore diet compositions in tropical areas where carbon isotope composition reflects roughly the proportions of C4/C3 –photosynthesizing plants (roughly grass vs. browse) in diet, but outside tropical areas all plants, grasses included, are C3 photosynthesizing and the carbon isotope composition varies also considerably according to so called canopy effect (open vs. closed environment), not just according to diet, and thus isotopes would not have allowed us to estimate the amount of grass vs. browse in the Pleistocene European ungulates as consistently and quantitatively as we could with mesowear analysis.

“Third, mesowear has been specifically shown to reflect average grass vs. browse compositions in the diets of ungulate populations, without being significantly obscured by other environmental variables, such as climate or environmental openness (e.g. Louys et al. 2012, Kaiser et al. 2013). Even if mesowear is a ‘physical observation’ as you say, it has been shown to specifically reflect the amount of abrasive dietary items (mostly grass) in herbivore diets.”

The authors focused on fossil-rich sites, where they could study between 3 – 10 fossils of each species.  They made sure to include species that were browsers, grazers and mixed-feeders.

Screenshot of Figure 1 from “Patterns of diet and body mass of large ungulates from the Pleistocene of Western Europe, and their relation to vegetation.” Palaeontologia Electronica19.3.32A: 1-58

 

“I owe thanks to my co-authors who knew much of the available European Pleistocene mammal collections already, having experience on working on them for many years,” Juha responded when asked how they knew of or had access to so many fossils.

“Adrian Lister from the Natural History Museum of London in particular has a huge amount of knowledge and experience about Pleistocene mammal collections.

“I was also in contact with the curators of the museum collections, who gave me valuable information about the how much and what kind of material they have. Also, information about important fossil finds and numbers of specimens found have often been published before in scientific journals.

“The authors of this paper represent different fields of research experience on the various aspects of the study. I started to work on this research as a part of my PhD work, and I originally planned it with my PhD thesis supervisors Mikael Fortelius, Jussi Eronen and Heikki Seppä from the University of Helsinki.

“During the work, I visited the Natural History Museum of London, where I worked together with Professor Adrian Lister, whose expertise on British Pleistocene mammals, the NHM fossil mammal collections and mammal palaeoecology in general were very important for this work.”

Image of Professor Adrian Lister, Natural History Museum of London, with the mummified baby mammoth, Lyuba; photo courtesy of the Natural History Museum of London for this post.

 

This work was not without its challenges.  As with any study of fossils, there are limits to the number of fossils available.  While pollen record availability has increased, there is still so much more to be discovered.  And although some species–based on extant examples–do not exhibit sexual dimorphism in body size, the sex of most of the fossils they studied was indeterminate.

“Indeed, these were some of biggest challenges in this study,” Juha acknowledged, “but they were expected and nothing much could be done to completely avoid them. I would add that it was often challenging to connect the fossil mammals with associated pollen records, especially when the fossil pollen was not obtained directly from the mammal fossils. To succeed in this study, it was important to analyze lots of data in order to overcome these problems, and to ensure that the main results and conclusions of this study are robust despite of them.”

The authors of this paper considered numerous variables in their research, and they suggest that ungulate size has a lot to do with a number of factors.  This might seem obvious, but such has not been the result of past studies.  In particular, Bergmann’s rule, which stipulates that body size corresponds largely to thermoregulation (i.e.: big body size is the result of living in colder environments), has been supported before.

Bison bonasus (Artiodactyla), Kraansvlak, Netherlands;photo courtesy of Juha Saarinen. 

 

“[T]here has been a lot of discussion as to what ultimately explains the tendency of some (but not all) organisms to be larger in cold climate. This was actually one of the main questions I discussed in my PhD thesis,” wrote Juha. “Already in 1950s some researchers (e.g. Scholander 1955, Irving 1957, Hayward 1965) pointed out that increase in size alone would not give a large enough benefit for thermoregulation in cold climates, especially considering that mammals have far more effective mechanisms of keeping warm, such as thick fur.

“Since then, many authors have noted that while there is a tendency of mammals being larger in higher latitudes, there are a number of exceptions to this ‘rule’ and heat conservation alone would not explain it.

“However, body size in mammals does correlate with food quality and availability and this seems to explain most of the body size patterns observed in mammals (e.g. Rosenzweig 1968, Geist 1987, Meiri et al. 2007, McNab 2010). For example, many herbivorous mammals tend to be larger at higher latitudes because food quality is better there (e.g. because of fertile soils created by glacial erosion and because plant defense mechanisms are lower), and thus predators eating them also tend to be larger there, but for example brown bear body mass does not correlate with latitude but with distance to nearest salmon spawning areas. On the other hand, population density also affects body size through resource availability: individual body size has been noted to decrease in many species of mammals when population densities are high leading to increased intraspecific resource competition (e.g. Wolverton et al. 2009).”

The authors of this paper argue that environment–climate, open or closed vegetation, food availability and quality–and species social structure–large or small herds–affect body size.

“[T]here are many (often interconnected) factors which together affect body size,” Juha explained. “This makes it quite complicated and challenging to study what ultimately regulates body size in mammals (and other organisms).

“In fact, our results do not support Bergmann’s rule as such, because even if our analyses show that larger sizes seem to occur in some species in open environments, this is not because of low temperature, as some of the open environments were in fact quite warm. Also, we often see that when one species was particularly large in an environment, another species was particularly small under those same conditions. E.g., we found out that red deer (Cervus elaphus) tends to be large in open environments, but wild horse (Equus ferus) tends to be small in those same environments. Thus, our results do not support the assumption of Bergmann’s rule or any other “single-cause” explanation for ungulate body size variation.

“What ultimately regulates ungulate body size is primarily food quality and availability, which is affected by the interplay of vegetation structure (regulated by environmental temperature, precipitation and soil fertility), interspecific resource competition (depending on the presence of competing species) and intraspecific resource competition (depending on population density). For example, species with large population densities in open environments, such as reindeer, bison and wild horses, could be small under those conditions because of increased intraspecific resource competition, whereas species with smaller population densities in open environments, such as red deer are large under such conditions, e.g. because of abundant, high-quality food and diminished plant defense mechanics. This is also the main conclusion concerning our results of Pleistocene European ungulate body size variation.”

“I think that studying how mammals in the past interacted with their environments is important for understanding how these interactions work in general,” he concluded. “At present, environments and their mammal faunas are so heavily influenced by human activities, and they have lost so much of their original diversity, that I believe that we simply need to study fossil mammals and their palaeoenvironments to better understand how these things have worked and ‘should usually work’ in nature.”

Equus ferus (Mongolian wild horse and Perissodactyl), Lippeaue, Germany;photo courtesy of Juha Saarinen. 

It was a great honor and pleasure connecting with Dr. Juha Saarinen!  Reading this paper and gaining more insight about it from him was absolutely fascinating!  An enormous thank you to him for all of his generous help!!

Additionally, Dr. Saarinen was extraordinarily kind and helpful in clarifying points about the research that I had misunderstood.  That is always appreciated.  THANK YOU!!

Reference:

1. Saarinen, Juha, Eronen, Jussi, Fortelius, Mikael, Seppä, Heikki, and Lister, Adrian M. 2016. Patterns of diet and body mass of large ungulates from the Pleistocene of Western Europe, and their relation to vegetation. Palaeontologia Electronica 19.3.32A: 1-58 palaeo-electronica.org/content/2016/1567-pleistocene-mammal-ecometrics

Fossil plant defenses and the rise of African savannas

 

Endangered Rothschild Giraffe bending over eating the leaves from a small Acacia tree in Lake Nakuru, Kenya, Africa – notice the thorns!; photo: David Gomez, from Getty Images

 

We are still a long way from understanding the animals* around us, but in many regards, it’s a lot easier to infer the emotions and actions of other mammals than it is to grasp anything about plants.

I know, for example, when my cats want attention, when they’re hungry, and—especially when one of them ambushes my legs with her furry paws—when they want to play.

I can’t say the same for my plants.  I’m not sure I ever think of them in terms of having emotions.  Am I concerned with their growth? Absolutely.  Do I make sure to water and feed them appropriately?  Yes.

But I suspect most of us think of plants in a completely different way than we think of animals.

This particular view of life on our planet was expressed in “Jurassic Park.”  After their initial introduction to the dinosaur park created by John Hammond and his team, the invited scientists gathered for lunch.  Mathematician Ian Malcolm (played by Jeff Goldblum) expressed his doubts and concerns about the park.  This led the others to offer their opinions as well.  Paleobotanist Dr. Sattler (played by Laura Dern) stated:

“Well the question is: how can you know anything about an extinct ecosystem?  And, therefore, how could you ever assume that you can control it?  You have plants in this building that are poisonous. You picked them because they look good, but these are aggressive living things that have no idea what century they’re in, and they’ll defend themselves. Violently, if necessary.”

Dr. Ellie Sattler (played by Laura Dern), Jurassic Park, 1993, Universal Studios

That very statement (albeit in a movie) challenges the conventional view of plants on this Earth.  Rather than simple sedentary life forms, it suggests that plants are more complex, engaging in the world around them, just as we know animals do.

And once you start thinking about plants defending themselves—taking an active part in the world around them rather than simply existing and having things done to them—it changes how you look at everything around you.

Scientific research into the realm of extant plant communication, defense and even participation in community is relatively new.  Dispersal of that scientific knowledge to the general public is even newer.

Remarkably—given how much we have yet to learn about existing plants—scientists from South Africa, Canada and the United States published research regarding the possible origin of African savannas, an origin that has roots** in plant defense millions of years ago.

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An example of an African savanna: Mt Kilimanjaro & Mawenzi Peak, clouds, grassland, and Acacia; photo: 1001slide, from Getty Images

 

A significant amount of land in the Miocene belonged to savannas, pushing forests to recede where they once flourished.  Some have attributed this to climate change; others to a change in the amount of carbon dioxide in the atmosphere.

The authors of “Spiny plants, mammal browsers, and the origin of African savannas”, published in PNAS this September, found a striking correlation between savannas, the evolution of plant spinescence, and the rise of ancient bovids.

“Savannas grow in climates and on soils that also support closed forests. So there is no ‘savanna climate’ uniquely predicting where they occur. Their rather abrupt appearance in the Miocene implies the emergence of new ecological processes favouring grasses at the expense of forest trees,” wrote Dr. William Bond of the University of Cape Town, one of the co-authors of the paper.

But how to even begin?  The fossil record, in general, doesn’t contain everything scientists would need to completely recreate any particular ancient ecosystem.  Where one might find animal fossils, that same rock may not preserve plant fossils, and vice versa.

The authors drew upon knowledge of today’s African megafauna, how it impacts existing ecosystems, and compared that with information about African fossils from the Miocene.  Elephants, for example, are known to knock down trees.  Antelopes, sheep, deer and other browsers  maintain open ecosystems today. Could their ancient ancestors have done the same?

“We had worked on fire as a major factor promoting [the spread of savannas,]” explained Dr. Bond. “We used a marker, underground trees, of fire-maintained higher rainfall savannas to explore their origins. Our dates of the emergence of ‘fire savannas’ in Africa were remarkably convergent with dates for ‘fire savannas’ in South America (cerrado) and also consistent with the sparse fossil record (Maurin et al 2014, New Phytologist and Pennington and Hughes, same issue with a commentary on our paper). In drier savannas, grasses do not build up enough fuel to burn regularly.  We wondered whether mammal browsing may help maintain open savanna vegetation where fire is less important. We needed a marker of savannas with high herbivore pressure and chose spiny plants.”

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A sparrow sits amongst the large white thorns of an Acacia tree, Kenya; photo: Richard du Toit, from Getty Images

 

In other words, fire was originally thought to be the reason behind the rise of savannas.  Evidence of fire has been found in fossil charcoal,  in paleosols and in fossil teeth.  The authors of this paper expanded their research to include fossil mammals.  Knowing that today’s savanna plants defend themselves with thorns from browsing mammals, the authors wanted to see if these same defenses occurred in fossil plants.

They had an incredible tool to help with this task: the African Centre for DNA Barcoding.

 

Fig. S1. Types of spines. (A) Prickles: Zanthoxylum davyi. (B) Straight stipular spines: Vachellia robusta. (C) Straight stipular spines and stipular hooks: Ziziphus mucronata. (D) Straight thorns: Gymnosporia harveyana. (E) Hook thorns: Scutia myrtina. (F) Straight stipular spines and stipular hooks: Vachellia tortilis. (G) Stipular hooks: Senegalia nigrescens. Es, epidermic spine; L, leaf; Ls, leaf scar; Ss, stipular spine; T, thorn (i.e., branch with a sharp tip); from Charles-Dominique et al. http://www.pnas.org/cgi/content/short/1607493113

 

What they discovered was that savannas existed before the large-scale evidence of fire, rather than simply because of it.  Thorns didn’t appear until well after the rise of proboscideans and hyracoids, indicating that neither of these species triggered the need for that specific physical defense.  Interestingly, the rise of ancient bovids (and possibly ancient giraffoids) corresponds to the emergence of thorns in the Miocene.  Ultimately, they found that spinescence evolved at least 55 times.

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Browsing impala — a type of modern antelope (bovid); photo by: annick vanderschelden photography, from Getty Images

“One might think that spines are a general defence against an archetypal mammal herbivore,” Dr. Bond wrote. “So we were most surprised at the late emergence of spines in African trees. We speculate that spines don’t work to limit food intake by proboscideans (a reasonable guess based on extant elephant feeding) and also hyracoids. But just why hyrax don’t select for spines is an intriguing puzzle. Observations on the remaining few hyrax species may be informative.”

“Physical plant defences are far less studied than chemical defences. They seem to resemble more plant-pollinator or plant-disperser interactions in being adapted to particular types of herbivore with particular modes of feeding. Spines don’t work for monkeys, for example, with their ability to pluck leaves with their fingers and manipulate branches. I have also worked on plant physical defences against extinct giant browsing birds (moas in New Zealand, elephant birds in Madagascar). They are utterly different from spines and exploit the limitations of beaks and the ‘catch and throw’ swallowing mechanism of the birds.”

“Molecular phylogenies dated with fossils were our main tool for exploring the past,” he continued. “Molecular phylogenies for mammals have been controversial tending to give much older dates for lineages than the fossil evidence. We used a recent phylogeny for bovids produced by Bibi (2013, BMC Evol Biol) using many more fossils than usual for calibrating the molecular phylogeny. Christine Janis, in an early e-mail exchange, kindly pointed us to the excellent book on Cenozoic mammals of Africa (Werdelin, Sanders 2010), among others, for help in reconstructing herbivore assemblages at different times.”

 

Screenshot of species distribution and environment correlates; from Charles-Dominique et al. http://www.pnas.org/cgi/content/short/1607493113

 

The sheer size and scale of the African continent is overwhelming.  This recent paper doesn’t focus on part of it; it encompassed the entire continent. When I asked Dr. Bond if this project was as enormous as it seemed, he wrote, rather amusingly, “Yes! Very daunting for me. People used to publish papers analyzing environmental correlates of single species distributions. Our team did the analyses for 1852 tree species. The mammal data was also enormous. Seems the younger generation is used to these vast data sets. I was amazed at the speed at which results became available.”

The list of websites cited in this paper (http://www.ville-ge.ch/cjb/; http://www.theplantlist.org; http://www.naturalis.nl/nl/; http://www.gbif.org; http://www.fao.org/home/en/) and the information those websites provide prompted me to ask whether it was fair to say that this paper could not have been written at an earlier point in time (without that online data). I also wondered if it was fair to say that science (in instances like this, where researchers share data online and make it accessible to others worldwide) is becoming more cooperative or team-oriented.

He responded: “You are absolutely right about ‘more cooperative and team-oriented’. The availability of massive data sets, and the tools to analyze them, has made analyses such as ours possible. Our team included people with diverse skills and knowledge. Hard to see how one or two researchers could have pulled this off.”

“The study is the outcome of several years of collaboration between systematists led by Prof Michelle van der Bank of the University of Johannesburg, ecologists working with me at the University of Cape Town, and a phylogenetic specialist, Prof Jonathan Davies from McGill University in Canada and an old friend of Michelle.

“Michelle, who heads up a DNA barcoding unit, had invited me to work with her group on ecological questions that could be addressed with molecular phylogenies. It has been a wonderful collaboration.

“Tristan Charles-Dominique worked with me as a post-doc bringing new skills in the French tradition of plant architecture. He made great strides in understanding plant traits of savanna trees. His work on physical defences against mammal herbivores is the most original and important contribution since the 1980s in my view.

“Gareth Hempson,  also an ex post-doc with me, had spent a great deal of effort compiling a map of African mammal herbivore abundance, and species richness, as it would have been ~1000 years ago (Hempson, Archibald, Bond 2015, Science). He combined mammals into functional groups which helped enormously in simplifying ecological functions of different groups. His participation allowed us to link the key mammal browsers to concentrations of spiny plant species.”

“It’s a rare combination of people to address a big question.”

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Gerenuk, or giraffe antelope (Litocranius walleri) feeding from a bush; photo: 1001slide, from Getty Images

 

————————–

*including our own species!

**an unintended pun

---

It was a great honor and a great pleasure connecting with Dr. William Bond, who–despite a very busy schedule and an unfortunate stay in the hospital–responded so quickly to my inquiries!  Thank you so much, Dr. Bond!  The research by you and your colleagues has opened a fascinating door for me!!

 

References

Spiny plants, mammal browsers, and the origin of African savannas,Tristan Charles-Dominique, T. Jonathan Davies, Gareth P. Hampson, Bezeng S. Bezeng, Barnabas H. Daru, Ronny M. Kabongo, Olivier Maurin, A. Mathuma Muaysa, Michelle van der Bank, William J. Bond (2016), PNAS, vol. 113 no. 38. DOI: 10.1073/pnas.1607493113

What Plants Talk About, Nature, PBS, 2013

Savanna fire and the origins of the ‘underground forests’ of Africa, Olivier Maurin, T. Jonathan Davies, John E. Burrows, Barnabas H. Daru, Kowiyou Yessoufou, A. Mathuma Muaysa, Michelle van der Bank, William J. Bond (2014), New Phytologist, DOI: 10.1111/nph.12936

Jurassic Park, (movie) Universal Studios, directed by Steven Spielberg, 1993

 

 

Further FASCINATING information on contemporary plants

How Trees Talk to Each Other, Suzanne Simard, TED talk, June 2016

Published papers by Suzanne Simard, University of British Columbia

The Hidden Life of Trees, Peter Wohlleben, 2016, Greystone Books

How Trees Fight Back, Dave Anderson, Chris Martin, and Andrew Parrella, “Something Wild,” NH Public Radio, September 23, 2016

The Herbivore Elicitor-Regulated1 (HER1) gene enhances abscisic acid levels and defenses against herbivores in Nicotiana attenuate plants, Son Truong Dinh, Ian T. Baldwin, Ivan Galis, Plant Physiology,162, 2106-2124, 2013. doi:10.1104/pp.113.221150.

Plant Kin Recognition Enhances Abundance of Symbiotic Microbial Partner, Amanda L. File, John Klironomos, Hafiz Maherali, Susan A. Dudley, PLOS One, September 28, 2012.

Fitness consequences of plants growing with siblings: reconciling kin selection, niche partitioning and competitive ability, Amanda L. File, Guillermo P. Murphy, Susan A. Dudley, Proceedings of the Royal Society B, vol: 279, issue 1727, 2012. doi: 10.1098/rspb.2011.1995

 

Persistence Cave: A rich resource for paleontological research

Caves whisper exploration and discovery.

Anyone who has ever set foot in a cave of any size cannot help but wonder what lies beyond, what lurks in the crevices, the darkness.  Stepping into a cave is stepping into the entrance of mystery just waiting to be revealed.  In a world that has been largely tamed to fit the human species, there are few spaces that still hold an element of danger.  These unknown spaces beckon to the adventurous: “Explore me!” And who wouldn’t answer that call?

Me, that’s who. I am perfectly happy learning about the discoveries in caves from other people, thank you very much.

For people like me, Twitter and blogs have provided tantalizing glimpses of such explorations the world over.  And one of the more fascinating adventures has taken place at Persistence Cave, just one cave of many at Wind Cave National Park, South Dakota.

“Wind Cave National Park is full of fossils. Almost everywhere you go there’s going to be fossils: in the cave and at the surface. So Wind Cave National Park actually has [perhaps] 30-40 fossil sites.”

PhD student Jeff Martin explained more about the work he and his colleagues conducted there last season as he and his wife were literally driving to Texas to begin a new chapter in their lives. He was in the moving truck; his wife was in the jeep ahead.  Jeff and I had been in touch by email from time-to-time over the past year. As luck would have it, and thanks to his seemingly unending generosity, the time to discuss Persistence Cave by phone was while he was on the open road.

Wind Cave—as we know it now—was named because of the air that blows through an opening within.  It was considered a sacred place to the Native Americans long before settlers knew of its existence.  The Lakota people refer to the Black Hills (where Wind Cave is located) as ‘He Sapa’, (although it is listed as ‘Paha Sapa‘ on the Wind Cave National Park site).  Eventually, in 1903, it became the 8^th National Park, but the first one to center around a cave.

Persistence Cave, a much smaller and less-explored cave in the park, was discovered by accident by Marc Ohms, spelunker and physical science technician for the park, in 2004.  His initial foray into the cave was brief: moving a cap rock, peering inside, seeing a rattlesnake, and deftly removing himself from the opening.

But its value as a fossil site was discovered thanks to another member of the park.

“Rod Horrocks, Wind Cave National Park Physical Scientist, in 2013, collected some sediment for preliminary analysis to see whether the site is paleontologically productive,” Jeff explained by email earlier.

It was, and this analysis is what eventually brought several scientists from diverse locations together.

Rod Horrocks sent the material to Dr. Jim Mead, Persistence Cave Project Leader, then at East Tennessee State University, where Jeff was a Master’s student at the time.  Jeff eventually moved to the University of Maine for his PhD, where Dr. Jacquelyn Gill was his advisor.

“Sharon Holte, PhD Candidate at the University of Florida, was also a previous Master’s student of Jim’s, as well as Dr. Chris Jass at the Royal Alberta Museum,” wrote Jeff, explaining the connections between the Persistence Cave teammates. “He knows that we each excel in different aspects of vertebrate paleontology, and he invited each of us to collaborate on [and] bring our expertise into the research project. I brought Dr. Gill with me to the Black Hills to see the cave and to learn how a paleontological excavation is usually conducted. She brings a different set of skills related to paleoecology and palynology.”

Also on the team are undergraduate Chason Frost from the University of Maine who studies horticulture.  His skills and those of Dr. Gill help the group understand that fossil plants and pollen found in the cave.

Sharon Holte, aside from being one of the three principal spelunkers in this dig, is in charge of educational components.  Chris Bell at the University of Texas Austin studies the fossil rodents; Dr. Chris Jass and Dr. Jim Mead study fossil rodents as well, but include fossil snakes.

“Each person has their role,” he said, “their own ecological-niche, if you will.”

And Jeff?  He is the “bison guy.”

“My PhD research and dissertation focuses on bison body size adaptation to climate change over the past 40,000 years and how does that evolutionary legacy influence the bison we ranch today,” he wrote before he graduated this past Spring. “To answer this, I am using Persistence Cave and other fossil sites in Wind Cave National Park boundaries to geographically isolate my variation to only local animals.”

Wind Cave National Park, currently home to 400+ extant bison, offers information on both fossil bison and their living descendants.

 

EPSON DSC picture; bison at Wind Cave National Park, public domain from the National Park Service

 

“Collectively, we (Jacquelyn, Chason, and I) will then also look at the pollen grains and macro-botanicals preserved in the sediment to reconstruct the paleoecology and paleoclimate of the Black Hills through the last 11,000+ years to today. This is [to understand] the climate and ecology the bison were living in at these times.”

But let’s get back to the cave itself.

Below is an image of Natural Trap Cave (another exciting fossil cave dig in Wyoming; photo from myfossil.org):

 

 

Compare that to an image of Persistence Cave from the top looking in (photo: Chason Frost as posted on Jeff Martin’s blog here):

 

 

 

 

And one of Sharon Holte peering out:

 

 

 

Finally, below is an image from the Rapid City Journal of “a tight spot in Wind Cave” (photo: National Park Service):

 

When I asked about how this image compares to the space within Persistence Cave, I was surprised by Jeff’s email response.

“The picture above is much larger than the cave we are working in,” he described of the 2015 dig.  “The cave is very narrow and only fits one person’s shoulder width and up to 1.5 shoulder widths in places. The vertical height is similar to the above photo though.”

“I’m a broad shouldered fella’ and very, very tall,” he continued by phone recently. “The space in there to turn around is not quite enough for me, so I’d have to climb in and then climb backwards out.”

“Chris Jass and I are both the exact same height. Chris is a far more experienced spelunker, and even Chris wasn’t going in there.”

Sharon Holte, Chason Frost and Jim Mead were the principal spelunkers for the site.  Only one person could be in the cave at a time, and their only source of light came from a headlamp.  Trowels, buckets and ropes: their only tools.

 

“I thanked them endlessly, and I still thank them for all the work they were doing down in there,” Jeff said of his three colleagues. (A video of Sharon’s work in the cave can be found here.)

Work involved taking chunks of sediment in buckets out of the cave, tagging it, labeling the information (where that sediment appeared on the appropriate grid, at what depth, etc.), bagging that sediment, and then sending it down—by zipline, of all things!—to the truck below, where it could be taken to be screenwashed by other team members. (You can see a video of that process here, on Jeff’s blog.)

 

Screenshot of tweet during the 2015 Persistence Cave (#cavebison) dig

 

Their fossil discoveries have been diverse. Jeff wrote that “[a] camelid, (the species is unknown at this time), has been an extraordinary find. We have 5 different kinds of snakes and at least 5 different species of bats. [A] pika is also an intriguing find.”

 

 

 

 

 

Screenshots of some of the many tweets during the 2015 Persistence Cave (#cavebison) dig

 

“One of the fun things that we ran across was a ton of Ponderosa pine needles,” he mused later by phone. “That’s the primary tree out there now.  Today, they’re mostly a two-needle bundle. In the past, it seems as though they were a three-needle bundle. And we don’t know exactly what that means yet.  So we’re trying to figure out if that means anything at all; if it’s a genetic difference; or if it truly is an environmental difference that it’s responding to.”

 

Screenshots of some of the many tweets during the 2015 Persistence Cave (#cavebison) dig; the scientists involved in this dig didn’t just conduct research, they also conducted outreach to the larger public through social media.

 

 

Work did not continue as expected on the site this year for a number of reasons, but it’s not over yet.  Studies on the fossils continue at the University of Maine (pollen and plants); the bison fossils have travelled with Jeff to Texas A&M University where he is now in wildlife sciences; and the rest of the fossils are housed at The Mammoth Site, where Dr. Jim Mead is currently Chief Scientist and Director.

The Mammoth Site is another major connection between many of the team members, as they have each “worked [there] at some point…over the last 40 years.”

As many know, that site is a paleontological (and proboscidean!) goldmine turned museum, thanks to the work of many, including the late Dr. Larry Agenbroad.  Over 60 mammoth fossils have been discovered there to-date, among other fossil species.

Image of the bonebed at The Mammoth Site where excavations continue to this day

 

“He was probably THE reason that I got into the School of Mines [as an undergrad] and was also the reason I got into paleontology,” Jeff said of Dr. Agenbroad.

“I’m not alone,” he continued. “There are several of us that are like that.  We all stem from Larry.”

The reverence in his voice was not difficult for me to understand.

Jeff’s introduction to this paleontologist began when he was much younger, through the 2000 documentary “Raising the Mammoth.” The film focuses on the Jarkov mammoth, and Bernard Buigues’ attempts to excavate it.  The team Buigues calls upon to help include some giants of proboscidean research: Dick Mol and Larry Agenbroad.

A year or so after seeing that film, Jeff’s family traveled to The Mammoth Site.  It was winter in South Dakota, and, he said, his family basically had “the run of the whole place.”  With a graciousness I am sure permeates everyone who works at that site, one of the interpreters (‘docents’) offered to bring Dr. Agenbroad out to meet them.

“There’s 8-year-old me that’s just giddy with joy to be able to meet one of my idols,” Jeff shared with no small amount of enthusiasm. “And then he said, ‘You’re a little bit too young to work for me. Come back when you’re older.’”

“So that’s exactly what I did. I worked for him in [the summers of] 2007 at the Hudson-Meng Bison Kill Site and  2008 and 2009 at the Mammoth Site as an intern while I was at the School of Mines.”

Dr. Agenbroad passed away two years ago, followed by his wife, Wanda, a month later.  This saddened me as someone who did not know him closely; I could only imagine how this affected Jeff, who had.

“I’ve made my peace with it,” he acknowledged, and then said something that truly moved me: “I have several things that Jim [Mead] gave me…and one of them is a pocketknife that I carry on me every single day. One of the same pocketknives that Larry carried on him every single day. So I’ve got Larry with me, right now, as a matter of fact.”

Jeff and his colleagues hope to resume work at Persistence Cave next year.

As we discussed some of the findings from last year’s dig, he said, “The oldest date right now at Persistence Cave is at 39,000 and the youngest date is at 3,200.  We have some 37,000 years of deposits with bison throughout. And we also have [modern-day] bison living at the surface!”

Jeff’s research, both of Persistence Cave and of Project Bison, underscore his passion for this animal, as well as the desire to understand its ecological significance.

“I’m looking at both the fossil record and looking at their body size, using the calcaneum [heel bone] as the proxy for body mass. And then also comparing that to modern bison that have just recently passed away within the past 1-3 years.  That’s what I was doing this past summer: going to carcass sites and measuring their calcanea. The unique thing about Wind Cave is that they have almost every single animal microchipped. So they can track this animal throughout its life. On top of that, they bring them in once a year and weigh them. So now we have a known mass of these animals and now a known measurement, because I measured some of their calcanea.

“I’ve got some [fossil bison calcaneal] measurements that go up to 180 millimeters, and I also have Bison bison today that the longest that I’ll find are 130 millimeters.  So quite a body size change in between the fossil and modern.”

Jeff presented some of his research at last year’s Society of Vertebrate Paleontology (SVP) meeting in Dallas.

Describing the results, he explained, “As it gets colder, bison get bigger.  As temperatures are increasing, bison get smaller. That has modern day application to the bison industry today. If we’ll have smaller bison with future global warming, we’re going to have to change our management options.”

As I pondered all of the information Jeff had shared with me about the work he and his colleagues had done, I couldn’t help but go back to the images of how small the cave actually is. If Wind Cave National Park has an abundance of fossil sites, why go through the trouble of trying to access this one?

“Surface localities often represent a one-time event,” he explained. “Persistence Cave represents many events over a long period of time. That’s the unique part of this locality.”

I will continue to enjoy their adventures from the safety of my computer!

 

**************

Jeff Martin: you were extraordinarily generous with your time and responses to my myriad questions.  Likewise, I am in awe of how open you were with your experiences.  For being willing to share all of this, I am truly grateful.  It was an honor and a pleasure connecting with you!

When #CaveBison starts up again, you can be sure it will be on Twitter!  Follow these scientists:

@BisonJeff

@JacquelynGill

@SharonHolte

@Pocket_Botanist

@MammothSite

 

You can follow Jeff’s research here and here. 

Jacquelyn Gill is one of three hosts of the podcast, Warm Regards, which discusses climate change.

 

Sousatitan: Brazil’s oldest sauropod bone found in a sea of trace fossils

One man happened to see the bone; one scientist happened to see the picture he posted online.

These two chance occurrences brought about a remarkable discovery: the first fossil dinosaur bone to be found where none have been found before.

Not only is it the first dinosaur bone in the area, it is also the oldest sauropod bone in Brazil to-date, a new as-yet-unnamed species of titanosaur.

Luiz Carlos Gomes was looking for fossil footprints in Sousa, Brazil. Hundreds upon hundreds of trackways, footprints and other trace fossils have already been found in Paraíba–a state in the West coast of that country and where Sousa is located–in an area known as the ‘Valley of the Dinosaurs‘ (‘Vale dos Dinossauros‘). But actual bone fossils? None.

None, that is, until he recognized actual bone within rock.

“He was the main [person] responsible for the discovery,” wrote Dr. Aline Ghilardi, paleontologist at Universidade Federal de São Carlos, in an email. “Luiz Carlos is a very curious retired gentleman whose hobby is to look for dinosaur footprints. He found the bone by chance (it was still inserted into the rock, so he knew it was not only a recent bone), took a picture of it and posted on the internet. Searching information about the area, I found the photo by chance, and, knowing the importance of the discovery, immediately got in touch with him.”

 

Images of fossil footprints found in the Valley of the Dinosaurs (Vale dos Dinossauros) in the state of Paraíba, Brazil; screenshots from the Colectionadores de Ossos (Bone Collectors) video; courtesy of Aline Ghilardi and Tito Aureliano.

 

Image of Luiz Carlos S. Gomes and Dr. Aline Ghilardi; screenshot from the Colectionadores de Ossos (Bone Collectors) video; courtesy of Aline Ghilardi and Tito Aureliano.

 

That bone was the subject of a paper published this past July in Cretaceous Research by Aline Ghilardi, Tito Aureliano, Rudah Duque, Marcelo Fernandes and Anusuya Chinsamy-Turan (“A new titanosaur in the Lower Cretaceous of Brazil“).

 

Fossil of the sauropod bone found in-situ in Sousa, Brazil, nicknamed ‘Sousatitan’; courtesy of Aline Ghilardi.

 

Through its bone histology, they believe this fibula belonged to a young titanosaur, rather than a small adult.  They noted rapid growth, and they highlighted an aspect within the bone that intrigued them.  In their paper, they point out that “…the lateral part of the bone wall has what appears to be bone tissue not formed in laminae and a predominance of longitudinally orientated vascular channels within a woven bone matrix.”

“This suggests that different parts of the bone wall [are] growing at different rates,” wrote Dr. Anusuya Chinsamy-Turan, paleobiologist and professor at the University of Cape Town, “i.e.: the rate of bone formation is not constant around the whole cross section of the bone wall.”

Image of “fibrolamellar bone tissue in the process of being deposited on the medial side of the bone wall” and Anusuya Chinsamy-Turan; screenshot from the Colectionadores de Ossos (Bone Collectors) video; courtesy of Aline Ghilardi and Tito Aureliano.

Their comparisons with other titanosaur fibula indicate it is a new species, although the authors are cautious about this.  And using a complicated mathematical formula, they can estimate the size of Sousatitan, the nickname they have given this dinosaur.

Tito Aureliano, a PhD student at the Universidade Federal de Pernambuco, helped elucidate how, equipped with a single fossil bone, they could make an educated guess about its size. His solution involved tweaking a previously published equation and quite a bit of ichnofossil measurement.  Keep in mind that the Valley of the Dinosaurs has at least 74 known sauropod footsteps.

Tito Aureliano; screenshot from the Colectionadores de Ossos (Bone Collectors) video; courtesy of Aline Ghilardi and Tito Aureliano.

 

“We used equations in two steps in our paper,” he explained by email, “because we needed to relate and compare one single fossil specimen to the abundant ichnospecimens from Sousa. The most accurate and mathematically secure way to do that (and [to avoid] speculation) was calculating hip height joint from footprints and total leg height from the bone we found.  We didn’t work with total length because that varies quite a lot in Titanosauria, and it wouldn’t be [scientifically useful].”

“First, we observed titanosaur tracksites from the same age as Sousatitan’s leg size.  We measured the diameter of every ‘back leg’ footprint available at Rio Piranha Formation outcrops.  Then, we calculated the hip height of all titanos that roamed the area at this formation and noticed there were a variety of sizes in individuals.

 

 

Fig. 4.; image from A new titanosaur from the Lower Cretaceous of Brazil, Cretaceous Research.

“Previous authors developed equations to predict general dinosaur hip heights from tracksites, but if you are working specifically with titanosaur ones, you should work with the Argentinian equation.  González-Riga found a complete articulated titano leg in the same area he has encountered large footprints that fit exactly in size with his fossil.  By using this evidence, he was able to develop this accurate equation to estimate hip height from a single titanosaurian footprint.

“Secondly, we had to estimate Sousatitan’s leg size. We had just one single bone. How did we do that?  In González-Riga’s paper I mentioned before, he also presented a formula to calculate total leg length from its skeletal elements.  The major problem is that it had so many variables and geometry elements in it.  It would be impossible [to use] if a scientist has only one or two of these elements.  So, I worked on the equation to simplify it into just three variables: femur, ulna and fibula length. H = ¼1.106*(0.96F + T), where H represents hip joint height, F is femur length, and T is tibia length.  Now colleagues with less titanosaur limb bones [can use] González-Riga’s original idea with what they have.”

 

A view of Sousatitan’s fibula (or ‘DGEO-CTG-UPFE-7517’), viewed from every angle; screenshot from the Colectionadores de Ossos (Bone Collectors) video; courtesy of Aline Ghilardi and Tito Aureliano.

 

 

Great depiction of the estimated size of Sousatitan (in black) with the fossil found; image from A new titanosaur from the Lower Cretaceous of Brazil, Cretaceous Research.

 

Tito continued, “‘Ok, a cool new formula with three elements. But you have just one! How did you do it then?’

“It’s simple morphometry.  I gathered limb bones from a lot of different titanosaur genera and measured the ration between these three bones. Then, I could estimate the theoretical size of the other limb bones.”

Sousa Basin stratigraphy; image from A new titanosaur from the Lower Cretaceous of Brazil, Cretaceous Research.

 

Coming from an area of the United States known more for ichnofossils than bone fossils, I share their excitement.

And yet, “internationally, for now, we have only observed colleagues’ mentions regarding the work and its importance,” wrote Dr. Ghilardi.

Fortunately, this sense of excitement seems to permeate Brazil.

“The discovery is getting lots of attention in Brazil, from both our colleagues and the popular media,” she continued. “The bone’s discovery was announced in all major newspapers of the country and, [thus far], in two of the largest television channels of Brazil.  Visits to the ‘Vale dos Dinossauros’ Park (where the bone is now housed) increased significantly after the first announcement of the discovery in popular media.  The dinosaur’s nickname got very popular and soon reached even Wikipedia in Portuguese.”

Dr. Aline Ghilardi; screenshot from the Colectionadores de Ossos (Bone Collectors) video; courtesy of Aline Ghilardi and Tito Aureliano.

 

When I asked what brought these six scientists–from Brazil and South Africa–together on this research, Tito Aureliano explained that he and Dr. Ghilardi are married.  In addition, he explained, “our friend, [Rudah] Duque, is a technician in paleontological preparation at PaleoLab (UFPE, Recife city). Prof. Barreto is the chief of the PaleoLab. We have been working together for the past four years visiting the least explored areas of NE Brazil in search of new Cretaceous fossils.

“Prof. Anusuya had previously assisted us in pterosaur research [that included] some histological observations. She possesses not only great knowledge on the subject, but she is also very polite and friendly. Aline and I think it was wonderful to work with her and to learn from her.

“Our friend Marcelo is the chief of the Paleontological Museum of the Universidade Federal de São Carlos. He is a renowned specialist in dinosaur ichnofossils (he is that guy that published the first urolite, ‘dinosaur pee‘).”

Dr. Marcelo Fernandes; screenshot from the Colectionadores de Ossos (Bone Collectors) video;  courtesy of Aline Ghilardi and Tito Aureliano.

 

Trace fossils from paper by Fernandes et al corresponding to liquid wastes (urolites!); screenshot from the Colectionadores de Ossos (Bone Collectors) video;  courtesy of Aline Ghilardi and Tito Aureliano.

 

Without doubt, the authors will continue to search for additional bone fossils in the area.

“The intention is to seek funding to continue doing searches in the region.  We hope to find more material in [the] Lagoa do Forno site (including other parts of the same individual) and also other promising localities,” Dr. Ghilardi wrote.

 

 

Location of the find and map of Brazil; image from A new titanosaur from the Lower Cretaceous of Brazil, Cretaceous Research.

 

“I believe it is worth mentioning the importance of the contact between researchers and the population,” she added.  “It is always a good partnership and yields good results.  The locals are interacting every day with the fossiliferous rocks, therefore, they are the most likely people to find materials such as this bone.

“[Making] people feel part of the scientific knowledge process is a very effective way to preserve paleontological heritage for future generations. And not only create a sense of protection about it….but also a sense of pride in their heritage and their land.  Finally, this can be a fundamental social change factor for the local population, which is so needed in so many respects.”

Referencing Sousatitan’s discoverer, Luiz Carlos Gomes, she wrote, “Today, he is very proud of [what has transpired since the initial find].”

 

Depiction of Sousatitan amongst larger sauropods of the same species; artwork by Marcos Paulo; courtesy of Aline Ghilardi and Tito Aureliano.

You can help the Bone Collectors continue to educate the public by donating here! 

 

It was a remarkable honor and pleasure connecting with Dr. Aline Ghilardi, Tito Aureliano and Dr. Anusuya Chinsamy-Turan. That cannot be stated enough! It was exciting to learn more about their incredible discovery, and they were very generous with their time and help. From New England to Brazil and South Africa: THANK YOU!!

 

References:

1. A new titanosaur from the Lower Cretaceous of Brazil, Aline M. Ghilardi, Tito Aureliano, Rudah R. C. Duque, Marcelo A. Fernandes, Alcina M. F. Barreto, Anusuya Chinsamy; Cretaceous Research, Vol 67, December 2016; http://dx.doi.org/10.1016/j.cretres.2016.07.001

Videos by the Bone Collectors (Colecionadores de Ossos), several authors of this research:

Further Information:

1. Bone Collectors – Colecionadores de Ossos: http://bonecollectors.org (website of several of the authors in this paper)
2. The Bone Collectors’ Blog: http://scienceblogs.com.br/colecionadores
3. Bone Collectors – Colecionadores de Ossos on YouTube: https://www.youtube.com/user/ColecionadoresOssos
4. Um novo dinossauro Brasileiro: blog post about the Sousatitan discovery by Aline Ghilardi on the Bone Collector blog
5. Occurrence of urolites related to dinosaurs in the Lower Cretaceous of the Botucatu Formation, Paraná Basin, São Paulo State, Brazil, Marcelo A. Fernandes, Luciana B. R. Fernandes, Paulo R. F. Souto, Revisita Brasileira de Paleontologia, July/August 2004
6. Dinosaurs Without Bones, Anthony J. Martin, 2014, Pegasus Books — (Dr. Martin includes an illustration of one of the urolites discovered by Fernandes et al in this book; he also discusses their research on pages 245-246!)

 

 

3D Printing Opens Doors to Research – Jennifer Webb

Right now, in Michigan, an undergrad is studying the contours of fossils found half way around the world. Fossils that, in fact, continue to reside in their country of origin: South Africa.  She hasn’t traveled there; she doesn’t have casts of the fossils themselves.  What she does have, and what is steadily becoming available to other organizations, is access to 3D printers.

Jennifer Webb, with help from her advisor, Rachel Caspari, has been comparing 3D replicas of the famous Homo naledi fossils discovered in 2013 to the casts of early Homo sapiens fossils found in the 1960s and 1980s. Both sets of fossils were found in South Africa: Homo naledi in the Dinaledi Chamber of the Rising Star Cave, and Homo sapiens at Klasies River Mouth.  But, so far, only one set has been dated.

Jennifer Webb w/MakerBot Fossils, photo by Monica Bradburn, courtesy of Central Michigan University

 

Jennifer’s goal: to determine the age of the Homo naledi fossils by comparing their physical attributes to this set of Homo sapiens fossils.

“Because the date [of Homo naledi] is unknown,” Jennifer explained, “we can use those traits to look and see if they’re similar [to the Homo sapiens fossils from Klasies River Mouth]. And if they are similar, then they are likely to be of a similar time period or age.”

This is important, as it would help us better understand where on the evolutionary chain Homo naledi can be found, and therefore, what physical attributes and possible social behavior developed when.

Klasies River Mouth Homo sapiens have been dated to about 120,000 years ago.  The caves at this location revealed periods of human occupation through sparse human fossils, shell middens and indications of ‘hearth activity’.  (Interestingly, one of the eggshells discovered belonged to an ostrich, a species that has not existed in the area since the Late Pleistocene.)

 

 

Klasies River Mouth Cave, South Africa; image taken by John Atherton, Flickr

In contrast to the small number of fossils at Klasies River Mouth, roughly 1550 specimens were excavated at Dinaledi Chamber—the largest set of hominin fossils found in the entire continent thus far.  Absent evidence of predator damage or remains, the 15 Homo naledi skeletons appear to have been placed in that cave deliberately.

 

 

Figure 3. Cartoon illustrating the geological and taphonomic context and distribution of fossils, sediments and flowstones within the Dinaledi Chamber. The distribution of the different geological units and flowstones is shown together with the inferred distribution of fossil material.
DOI: 10.7554/eLife.09561.005

 

“My professor and I,” said Jennifer, referring to Rachel Caspari, “as long as we’ve known about this species, we’ve always been interested in it.”

But the path to actually studying Homo naledi didn’t appear until this past October, when Central Michigan University opened its Makerbot Innovation Center, making it unique amongst public Midwest universities.

And with access to 3D printers, Jennifer was able to make use of the digital scans and images provided on Morphosource.org.

One of the Homo naledi fossils as it is being printed; image courtesy of Central Michigan University

Rachel Caspari and Jennifer Webb with a 3D replica fossil; photo by Monica Bradburn; courtesy of Central Michigan University

 

Regular 2D printing has become so fast, so cheap, and so easy.  3D printing, on the other hand, is not necessarily any of those things.  At CMU, the cost of 3D printing is $.15 per gram.  It can take anywhere from 2 hours to an incredible 24 hours for something to print, depending upon various factors.  Most of the Homo naledi fossils took between 2 – 4 hours to create.

Having access to physical replicas of the originals is, indeed, exciting, but one wonders what challenges this might also present.

“3D printers can only be so accurate,” Jennifer replied. “The ones that we use are accurate to .2 millimeter difference. So we would have to factor in that amount of error into any of our analyses.”

“When we’re looking at the 3D-printed [fossils],” she continued, “they no longer have the coloring that the [original] fossils would have, which can also sometimes better indicate any dips or grooves or mounds. The best way we have to go around that is to look at the scans and pictures that we still have access to [from Morphosource] and compare them along with the 3D fossils that we printed.”

While researchers with access to the real Homo naledi fossils could perform isotopic analysis or radiocarbon dating, these procedures are both invasive and destructive to fossils.  Jennifer prefers to observe the physical traits themselves, preserving the fossils in their entirety.

“I love to be able to look at a set of bones, examine them, look at all their features and any marks or anything that’s on them and be able to tell a story from that,” she said.

This is no surprise, given that her interest in Forensic Anthropology—her intended course of study for her Masters—was prompted by the show, “Bones,” based on the life of Kathy Reichs.

Bones – Season 5 – “The Proof in the Pudding” – Emily Deschanel, Tamara Taylor and TJ Thyne; Photo by: Michael Desmond/FOX

 

“I was afraid that, because it was a TV show, in real life it wouldn’t be the same. So I shied away from it in college in the beginning and started off with a different major. And then I discovered a Forensic Anthropology course that was being offered at CMU, and I decided to give that a try.  Once I did, I realized that it was very similar; there were a lot of things that were exactly like what they portrayed on TV. So I started getting into it more, and my interest grew.”

Before graduating this December, Jennifer will be presenting her Homo naledi findings to the American Anthropological Association in November.

3D fossil replica, by Monica Bradburn, courtesy of Central Michigan University

 

Many, many thanks to Jennifer Webb for her time and her great responses to my questions! A very special thank you to Rachel E. Perkins for reaching out to me about this story.

Further Reading:

1. Geological and taphonomic context for the new hominin species Homo naledi from the Dinaledi Chamber, South Africa, Paul HGM Dirks, Lee R Berger, Eric M Roberts, Jan D Kramers, John Hawks, Patrick S Randolph-Quincey, Marina Elliott, Charles M Musiba, Steven E Churchill, Darryl J de Ruiter, Peter Schmid, Lucinda R Backwell, Georgy A Belyanin, Pedro Bomhoff, K Lindsay Hunter, Elen M Feuerriegel, Alia Gurtov, James du G Harrison, Rick Hunter, Ashley Kruger, Hannah Morris, Tebogo V Makhubela, Becca Peixotto, StevenTucker; eLife, 10 September 2015
2. We Are Made of Star Stuff, blog post on Twilight Beasts by K. Lindsay Hunter (one of the authors of the paper above and one Rising Star team who excavated the Homo naledi fossils)
3. Fossils Come to Life 8,500 Miles Away, CMU press release by Rachel E. Perkins

 

Forthcoming books on hominins:

1. Seven Skeletons: The Evolution of the World’s Most Famous Human Fossils, Lydia Pyne
2. Almost Human, Lee R. Berger and John Hawks
   

 

 

 

Stegodon: Does this ancient elephant have origins in Asia?

So much has been said in recent years about the wealth of fossils in China. Almost all of it about dinosaurs: exciting new species, feathered fossils, nest upon nest of dinosaur eggs.  There is no doubt that China holds exciting clues to the history of our planet; one has only to wait to hear of the next discovery.

Within the past few months, yet another exciting find was revealed, but this time about a little known mammalian ancestor: Stegodon.

 

Painting of a Stegodon by artist Hannah Stephens, hannahleestudio.com.

 

The name Stegodon, to me, evokes ‘dinosaur’, not ‘mammal,’ but this was, indeed, an ancient animal.  Its fossils resemble those of other similar mammals, from mastodons to mammoths to today’s elephants.

 

 

Figure 1: Reconstruction of four insular dwarf proboscideans with their respective mainland ancestors. Mainland proboscideans: 1, Palaeoloxodon antiquus; 2, Mammuthus columbi; 3, Stegodon zdanskyi [stegodon found in China]. Insular proboscideans: 4, Palaeoloxodon ‘mnaidriensis’; 5, Palaeoloxodon falconeri; 6, Mammuthus exilis; 7, Stegodon aurorae [a type of dwarf stegodon found in Japan]. Based on skeletons at Museo di Paleontología, University of Rome, Italy (1), American Museum of Natural History, New York (2), Taylor Made Fossils, U.S. (3), Museo di Paleontología e Geología G.G. Gemmellaro, Palermo, Italy (4), Forschungsinstitut und Naturmuseum Senckenberg, Frankfurt, Germany (5), Santa Barbara Museum of Natural History, Santa Barbara, U.S. (6), Taga Town Museum, Honshu, Japan (7). Photos 1–2, 4–7 George Lyras, photo 3 courtesy of TaylorMadeFossils.com, reproduced here with permission.

From The effect of area and isolation on insular dwarf proboscidea by Alexandra A. E. van der Geer et al; photo and caption courtesy of Dr. Alexandra van der Geer.

 

When Stegodon skulls with tusks attached have been found, many (but not all) of the tusks are close together–preventing the trunk (the ‘proboscis,’ from which this group gets its name; proboscis —> proboscidea) from hanging between them.

They lived in what is now Africa and Asia, causing continued debate over its place of origin. Until recently, the oldest known Stegodon fossil, a 6.5+ million-year-old partial molar from Kenya, was described by William J. Sanders in 1999.  That record changed this past December when Dr. Hong Ao and his colleagues published their results dating the sediment in the Lanzhou Basin, China, from which a number of fossils–including that of a Stegodon–were found.

And that Stegodon was found to be between 8 – 11 million years old.

 

Detail of the Geologic Time Scale, created by the Geological Society of America.  Stegodon is believed to have existed between the Miocene to the Pleistocene, a relatively small segment of time in Earth’s overall history, but still considerably longer than that of our own species!  (You can view the time scale in much better detail here.) 

 

The fossils of the Stegodon, along with at least 5 other species, were actually found in the 1980s by Professor Xing Zhang of Northwest University in China.  Given the length of time between the fossil excavations and the recent dating of these fossils, one might wonder why determining the fossil age took so long.

Dr. Ao, a scientist at the State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, and his colleagues state that western China does not have suitable material for radiometric dating, an oft-used method for this purpose.

When I asked why this was so, Dr. Ao replied by email, “Because volcanic activities are rare in western China during the late Cenozoic, it is difficult to find  in situ tephros or tuffs for radiometric dating (e.g., ⁴⁰Ar/³⁹Ar dating).”

Instead, they conducted a magnetostratigraphic study, one in which they determined the age of the rock through the polar reversal record.  Combining this with analysis of the fossils provided evidence that this Stegodon is 2 – 5 million years older than that of the Kenyan partial molar.

“We are indeed surprised by our dating results,” Dr. Ao continued, “which document that the Lanzhou Stegodon is the oldest Stegodon worldwide, although the Stegodon  fossil [was] not discovered by us. However, our dating results document it to be the oldest known Stegodon fossil.”

 

Images of Professor Yongxiang Li (from Northwest University) and his master student as well as several employed workers who helped to excavate mammal fossils, Lanzhou Basin, China; photos courtesy of Dr. Hong Ao.

 

Images of indricotherine fossils found in Lanzhou Basin, China; photos courtesy of Dr. Hong Ao.

 

Dr. Ao himself has been working with fossils in the Lanzhou Basin for 5 years.  When asked how  he and his co-authors chose to work together on this recent paper, he wrote, “I have collaborated with them on broad subjects before, thus I [invited] them to join [in] this research.”

Finding information about this extinct species is difficult.  Unlike mammoths or mastodons, Stegodon does not appear to be a popular ancient animal.

Fortunately, Dr. Alexandra van der Geer–paleontologist, indologist, ethno-zoologist and author –has not only studied this species, she very generously made herself available for questions.  Currently, Dr. van der Geer is an Associate Researcher at both the National and Kapodistrian University of Athens and the Naturalis Biodiversity Center in the Netherlands. She is part of the Isolario project, a project that studies biodiversity and cultural evolution within an island context.

When I asked why there was such a dearth of information on Stegodon, she wrote, “We can think of several reasons for this.”

“First of all, stegodons typically are the elephants of Southeast and East Asia, where most countries did not have the resources and opportunities most Western countries had when it comes to scientific research and excavations. These activities are costly, and since they don’t have a direct use in the sense that they don’t advance the medical, technical or economic levels of a country, they have, understandably, a lower priority. Furthermore, because of this region, half the publications (especially before the 1990s or so) you can find are in Chinese or Japanese, which is not very helpful to the [English-speaking] world.

“Secondly, stegodons are forest elephants. Forest areas are very unlikely places for the long-term preservation of organic materials: everything is eaten, digested or otherwise broken down into smaller components in no time. The tropical (warm, humid) climate of these forests is not helpful either, as decomposition is much faster here. Stegodon remains only have a chance to be preserved when (1) they are covered fast, such as with river sediments, volcanic ashes etc., (2) or are in an oxygen-free environment, such as sunken deeply into a swamp, (3) or were deposited in a natural fridge such as limestone caves where they are gradually covered in clayish sediment or [travertines]. The same is valid for Palaeoloxodon, the Old World fossil elephant, but Europe has many limestone caves, which are excellent for preservation (for a nice [travertine]-preserved negative skull, see Stuttgart museum: skull cast SMNS nr. 32888 from Bad Cannstatt).

“As you can deduct from these preservation issues, it is more likely to find molars and tusks than skeletal material, which is much softer. The vast majority of proboscidean findings all over the planet consists of molars and tusks, and that is not for nothing. Inherently this means that there is much more information about their dentition and diet than about their bodies.”

I was interested in understanding why Stegodons are portrayed as hairless animals, so very similar to contemporary elephants.  Was this just an artistic guess?

“The hairlessness of stegodons is not an artistic guess but a scientific guess instead,” Dr. van der Geer answered.  “Very large animals with thick skins (pachyderms) in a (sub)tropical environment are unlikely to have a significant hair covering. Elephants lost their hairs secondarily. The information for hair growth is not lost, and baby elephants still have a thin, woolly coat. Woolly mammoths lived in the cold, temperate zones, and needed hair, so they were covered in a thick layer of hairs, and for this is evidence (mummies preserved in the permafrost), but the other mammoths (M. meridionalis, M. columbi, M. exilis, etc.), [did] not, and it’s generally assumed that they had a light coat fitting to the temperate zones.

“Tropical and subtropical stegodons almost certainly did not have any coat that’s worth mentioning. Stegodons of temperate zones, however, may have been more hairy. Indeed, the lack of hairs makes them look more like today’s elephants.”

 

Photo of the two life-size models of Stegodon ganesa;photo courtesy of Dr. Gerrit van den Bergh (University of Woolongong, Australia); special thanks to Dr. Alexandra van der Geer.

 

“Note, however, that the proboscis is carried very differently. Their tusks are set very close to each other, so the proboscis doesn’t fit in between as in modern elephants, Asian and African alike. This means that the mobility of their proboscis was more restricted, relative to their living relatives.”

 

Fossils of Stegodon florensis insularis, from Flores, Indonesia; photo courtesy of Dr. John de Vos (Naturalis, the Netherlands); special thanks to Dr. Alexandra van der Geer.

 

Mandible (and holotype!) of  Stegodon timorensis; photo courtesy of Eelco Kruidenier (Naturalis, the Netherlands); special thanks to Dr. Alexandra van der Geer.  Anyone familiar with proboscidean teeth and jaws will recognize the similarities instantly.

 

But how do we know that Stegodon–a rather enormous animal–evolved into something smaller?

“[D]warfs and giants are relative. Something can be a dwarf, yet have a considerable size. When we speak of dwarf stegodons, we mean stegodons that are much smaller than their ancestors. For this, you have of course to have identical or otherwise similar elements from both the descendant and the ancestor in order to compare reliably,” she continued.

“The expectation is that dwarf stegodons must have existed on the islands, following the so-called island rule, according to which large animals get smaller in isolation. There is sound evidence that this rule still stands, and is even more pronounced for fossil species (see Lomolino et al., 2013, in Journal of Biogeography).

“Indeed, the many fossil molars from the Southeast Asian islands (‘Wallacea’) are all much and much smaller than the same molars from their mainland ancestors (see Van den Bergh, 1999). True, you first have to know what is the ancestor, and for this you need information about morphology, or how the molars, tusks, skulls and postcranial elements look like. After that, you compare the sizes.

“Note that if a molar is, for example, half the length of the same molar of its ancestral species, the body weight of that animal must have been a quarter of that of its ancestor! (the cubic law: linear reduction 50% means volume reduction 50% of 50%).”

Molar of Stegodon florensis; photo courtesy of Dr. Gerrit van den Bergh (University of Woolongong, Australia); special thanks to Dr. Alexandra van der Geer.  

 

“The most interesting dwarf stegodon is Stegodon sondaari, named after the Dutch palaeontologist Paul Yves Sondaar (1934-2003), expert in fossil insular mammals. This stegodon lived on the island of Flores about a million years ago, and weighted only about 15% of the weight of its ancestral species, S. elephantoides (see Van der Geer et al., 2016, in Journal of Biogeography, doi:10.1111/jbi.12743).

“Sondaar’s dwarf stegodon is not the smallest stegodon, that honour goes to the Sumba stegodon (S. sumbaensis), of only 8% of the original weight. Sondaar’s stegodon is interesting because it may have witnessed the arrival of early humans, possibly the ancestors of the Hobbit, or Homo floresiensis. Its fossils are contemporaneous with primitive lithic artefacts, dated to about a million years ago (see Brumm et al., 2010, in Nature 464, pp. 748–752).”

 

Molar (and holotype!) of Stegodon sompoenis; photo courtesy of Dr. Gerrit van den Bergh (University of Woolongong, Australia); special thanks to Dr. Alexandra van der Geer.  

 

“[R]ecently,” she concluded, “one of the island dwarf stegodons (S. timorensis of Timor) has been dated to about 130 thousand years ago (see Louys et al., 2016, in PeerJ 4:e1788). This excludes, according to the authors, an anthropogenic cause for its extinction, because humans had not yet arrived at the island.”

 

*****************

So many people helped with this blog post!  (But please remember that any errors are my own.)

Many, many thanks to Dr. Hong Ao (Dr. Ao Hong) from the State Key Laboratory of Loess and Quaternary Geology (Chinese Academy of Sciences) for his fascinating responses and the great images of fossil excavations in the Lanzhou Basin.  I am thrilled that he was willing to answer questions about his research and that of his colleagues! It was a great honor and a pleasure connecting with him!

I am indebted to Dr. Alexandra Van der Geer, who very kindly (and so very quickly–despite everything else she has going on!!) answered specific questions about Stegodon that I could not find anywhere else and who provided pictures of dwarf Stegodon fossils.  It was an equally great honor and pleasure connecting with her!

A mastodon-sized thank you to the amazing Dr. Katy Smith for providing needed and hard-to-find material on Stegodon fossils!

And an enormous thank you to artist Hannah Stephens for her depiction of a Stegodon as it may have appeared in life.  I am particularly moved by the warmth of its intelligent-looking eyes, and I love the tones within its skin.  I adore this picture.  I am grateful to have it in this post;  I am thrilled to have the actual painting hanging on my wall!  Please be sure to check out her artwork at: http://hannahleestudio.com or http://hstephens.blogspot.com

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References from Dr. Alexandra Van der Geer:

1. Brumm A, Jensen GM, van den Bergh GD, Morwood MJ, Kurniawan I, Aziz F, Storey M (2010) Hominins on Flores, Indonesia, by one million years ago. Nature 464, 748–752.
2. Lomolino MV, van der Geer AAE, Lyras GA, Palombo MR, Sax DF, Rozzi R (2013) Of mice and mammoths: generality and antiquity of the island rule. Journal of Biogeography 40, 1427–1439.
3. Louys J, Price GJ, O’Connor S. (2016) Direct dating of Pleistocene stegodon from Timor Island, East Nusa Tenggara. PeerJ 4:e1788
4. van den Bergh GD (1999) The Late Neogene elephantoidbearing faunas of Indonesia and their palaeozoogeographic implications; a study of the terrestrial faunal succession of Sulawesi, Flores and Java, including evidence for early hominid dispersal east of Wallace’s line. Scripta Geologica 117, 1–419.
5. van der Geer AAE, van den Bergh GD, Lyras GA, Prasetyo UW, Due RA, Setiyabudi E, Drinia H (2016) The effect of area and isolation on insular dwarf proboscideans. Journal of Biogeography, doi: 10.111/jbi.12743

References used in this blog post:

1. New magnetochronology of Late Miocene mammal fauna, NE Tibetan Plateau, China: Mammal migration and paleoenvironments; by Hong Ao, Peng Zhang, Mark J. Dekkers, Andrew P. Roberts, Zhisheng An, Yongxiang Li, Fengyan Lu, Shan Lin, Xingwen Li; Earth and Planetary Science Letters; 1o December 2015
2. Oldest record of Stegodon (Mammalia: Proboscidea); by William J. Sanders; Journal of Vertebrate Paleontology; Vol. 19, No. 4, Dec. 13, 1999, pp. 793 – 797
3. Fossil elephantoids, Awash paleolake basins, and the Afar triple junction, Ethiopia; by Jon E. Kalb; Palaeogeography, Palaeoclimatology, Palaeoecology; 1995, pp. 357 – 368
4. The effect of area and isolation on insular dwarf proboscidea; by Alexandra A. E. van der Geer, Gerrit D. van den Bergh, George A. Lyras, Unggul W. Prasetyo, Rokus Awe Due, Erick Setiyabudi, and Hara Drinia; Journal of Biogeography; 11 March 2016.
5. Magnetostratigraphy – concepts, definitions, and applications, by Cor G. Langereis, Wout Krijgsman, Giovanni Muttoni, and Manfred Menning; Newsletter on Stratigraphy, Vol. 43/3: 207–233, April 2010
6. Mammoths and Mastodons of the Ice Age, by Adrian Lister, Firefly Books, 2014
7. Mammoths, by Adrian Lister and Paul Bahn, University of California Press, 2007
8. The Proboscidea: Evolution and Palaeoecology of Elephants and Their Relatives, Edited by Jeheskiel Shoshani and Pascal Tassy, Oxford Science Publications, 1996

• Stegodontidae: evolutionary relationships by Haruo Saegusa, pp. 178 – 190, The Proboscidea: Evolution and Palaeoecology of Elephants and Their Relatives
• Palaeobiogeography of late Neogene African and Eurasian Elephantoidea by Jon E. Kalb, David J. Froehlich, and Gordon L. Bell, pp. 117 – 123, The Proboscidea: Evolution and Palaeoecology of Elephants and Their Relatives