Dr. Advait Jukar – Solving Mysteries in South Asian Fossil Communities

Dr. Advait Jukar–Deep Time – Peter Buck Fellow at the Smithsonian Institute–wants to really understand ancient ecosystems in South Asia, but doing so means beginning with some of the very basics. Challenges include not just a lack of available fossils from the region, but also the lack of detailed records from early paleontologists and a dearth of contemporary research.

He is, in a sense, an explorer.  (All paleontologists are.)  If we think of paleontology as a sculpture in progress, many scientists are working on the fine details.  Dr. Jukar, on the other hand, has the clay and the tools, but the sculpture itself hasn’t even begun to take form.

Consider what he has to work with: isolated proboscidean teeth and skulls, for example, collected by Hugh Falconer and his crew in the early 1800s.  They didn’t record where the bones were found, let alone where each fossil was in relation to the other.  Those who later described these fossils made dubious claims regarding the species.  And few people to this day have revisited this data or expanded upon it. 

 

Image of Dr. Advait Jukar at work with an Elephas hysudricus molar; courtesy of Dr. Jukar

 

Compare this to Maiasaura fossils in the Northwest US.  So many fossils of this species have been excavated that Dr. Holly Woodward Ballard has created the Maiasaura Life History Project.  Its goal is to uncover more details about this particular species than any other currently known extinct creature.  She has a wealth of data at her disposal. Unlike Dr. Jukar, the fossils she can study have been found fairly well articulated, very well documented, and in remarkable abundance.  There are adults, sub-adults, juveniles and embryos.  She and her colleagues are able to add to existing scientific literature using the latest technology.  It’s an exciting project with absolutely fascinating possibilities.

 

FIGURE 6. Survivorship curve for Maiasaura. Sample size of 50 tibiae was standardized to an initial cohort of 1000 individuals (assumes 0% neonate mortality). Survivorship is based on the number of individuals surviving to reach age x (the end of the growth hiatus marked by LAG x). Age at death for individuals over 1 year old was determined by the number of LAGs plus growth marks within the EFS, when present. Error bars represent 95% confidence interval. Mean annual mortality rates (μ^) given for age ranges 0–1 years, 2–8 years, and 9–15 years. Vertical gray bars visually separate the three mortality rate age ranges; courtesy Dr. Woodward Ballard for this post

 

 

 

But so, too, is Dr. Jukar’s intended research.   Focusing on the tail end of the Neogene, about 4 million years ago, through the Quaternary, he wants to understand herbivorous mammals—their community, their ecology, their biogeography.  It’s just a question of building the necessary foundation first.

“I started to compile all of these species lists,” he explained by phone, “and saw that there were lots of species of proboscideans in South Asia during that period of time.  We have gomphotheres; we have stegodons; we have elephants.”

One way to understand an animal’s impact on its environment is to assess its body mass.  How big (or small) were these animals?  And therefore, how much did they need to eat?  A larger animal would presumably need to eat a larger amount of vegetation.  Similarly, a larger animal might reproduce less frequently than smaller animals.  Body mass reveals clues about how an animal fits into the ecosystem.

However, he continued, “I hit a wall because there was no way for me to estimate how big these elephants were.  The problem was they were largely known either from skulls or teeth, and the traditional methods to estimate the weight of an extinct elephant were using shoulder height or the length and circumference of the long bones. So if I have a skull but I don’t have long bones, I’m sort of in a bind, because now I can’t estimate how much this animal weighed when it was alive.”

He looked to methods that others have used in the past. One method used by his colleagues at Howard University seemed to be a promising fit.  They used the occipital condyle breadth of seacows—a proboscidean relative–as an indicator for body mass.  Dr. Jukar’s PhD advisor, Mark Uhen, mentioned that this method had also been used on yet another large mammal: the whale. 

The occipital condyle is a bone found at the base of the back of the skull, connecting the skull to the spinal column.  It’s a relatively small bone.  Why would this have an impact on determining body mass?

“If occipital condyle breadth is correlated with the size of the animal,” Dr. Jukar said, “and if the occipital condyle is the point where the skull attaches to the rest of the skeleton, then maybe the size of the skull scales with the size of the overall body. And if that’s true, then maybe the occipital condyle breadth will scale with the size of the limb bones as well.”

 

Image of the back of a mastodon (nicknamed ‘Max’) skull at the Western Science Center in California displaying the occipital condyle bone resting on the metal stand; photo taken by Jeanne Timmons

 

In other words, if a paleontologist has but one skull of an extinct proboscidean and no other related fossils, can that person measure the breadth of the occipital condyle as a way to determine the size and weight of that animal?

To test this theory on proboscideans, he researched available scientific literature and visited a number of museum collections.  Ultimately, he and his two co-authors, S. Kathleen Lyons and Mark Uhen, compared the occipital condyle breadth to the length and circumference of leg bones within extant elephants and extinct relatives.  Two elephant species were studied, as were six gomphotheres, three mastodons and one stegodon.  

Image of a fossil Moeritherium at the Yale Peabody Museum; photo taken by Jeanne Timmons

 

While careful to note that this method has its limitations, the results were promising.  The equations are different for each proboscidean family (gomphothere body structure and size is not the same as that of a mastodon) and they do not work for some of the smaller proboscidean species, such as Moeritherium.  In layperson’s terms, this research works for taller, lumbering proboscideans, not those with much shorter limbs and a perhaps waddling gait. Their paper and its results were published in the Zoological Journal of the Linnean Society: A cranial correlate of body mass in proboscideans.

This, though, is just the tip of the iceberg in terms of Dr. Jukar’s research.  An enormous collection of fossils from India resides in the Natural History Museum of London.  Found in an area referred to as the Siwalik Hills (or the “Siwaliks”) at the base of the Himalayas, Scottish paleontologist Hugh Falconer and his team collected them in the 1800s.  Among them are several stegodon teeth and skulls. 

Image of Dr. Advait Jukar measuring a Stegodon ganesa fossil in the Natural History Museum of London collection; courtesy of Dr. Jukar

 

The two species of stegodon excavated from the Siwaliks are, to this date, known as Stegodon insignis and Stegodon ganesa.  The species have very similar teeth, but their skulls seem to differ greatly.  The skull of S. insignis, according to Dr. Jukar, is “almost triangular in shape with relatively small tusks,” which Falconer chalked up to sexual dimorphism.

“Which I just thought was the weirdest thing to ever say about stegodons because the skulls are clearly different. They’re clearly not sexually dimorphic.”

Moreover, there seems to be confusion regarding which fossils Falconer assigned to which stegodon species that continues to this day.  

“So what was going on in his mind? I have no idea.  It’s a problem! Because since then, people have said that both of these must be the same species without really truly investigating them. 

“Any Stegodon tooth that they’re finding in the Siwaliks, they’re calling Stegodon insignis or Stegodon ganesa or a hyphenated version of the two: Stegodon insignis-ganesa, which is taxonomic heresy.” 

And here Dr. Jukar was emphatic: “You CANNOT do that with the taxonomic code.”

“And that was Osborn’s fault.”

He was referring to Henry Fairfield Osborn, former professor then curator of the American Museum of Natural History in the late 1800s.

“Osborn [is known to have asserted], ‘I agree with what Falconer said, so I’m going to hyphenate these two words.’  Which created such a mess.  So we have no idea what’s going on there. 

“There’s a lot of work to be done with elephant taxonomy, biogeography and systematics and comparisons between China, the Levant, East Africa and India.”

 

Image of the Levant (Public Domain)

 

Dr. Jukar and other colleagues have also recently published papers on the earliest known fossil of Hexaprotodon, an extinct hippo, from South Asia, and the first record of a Hippaprionine horse (Plesiohipparion huangheense) from the Indian Pliocene.

He is currently working with Dr. Adrian Lister of the Natural History Museum in London to further understand the various proboscidean fossils in the Siwalik collection.

This is important work, but Dr. Jukar pondered its reception to the wider world.

“For a long time paleontologists have been criticized as being mere stamp collectors because we find things and then we name them and then we try to figure out in what larger group they belong to.  But that is the basis of our data.

“Only when I have a comprehensive sense of what the species are, when they lived and where they lived can I start doing these more complicated community-level analyses.

“But because the basic science of naming a fossil might not be very exciting, [as it doesn’t directly impact] human life very much, it doesn’t get a lot of attention. 

“I am definitely interested in the big picture questions of dispersal from Africa into South Asia, about the ecology of these groups, about how communities have changed through time, but I can’t really do a rigorous analysis until I figure out who the [basic] players are in this place.”

Image of Dr. Advait Jukar with a Mammuthus columbi (Columbian mammoth) skull; courtesy of Dr. Jukar

 

References:

  1. Colbert E. (1996). Henry Fairfield Osborn and the Proboscidea. In:  Shoshani J, Tassy P. The Proboscidea : evolution and palaeoecology of elephants and their relatives, Oxford: Oxford University Press, xxii – xxv
  2. Dr. Advait Jukar’s website: https://advaitjukar.weebly.com
  3. Jukar, Advait M., Lyons, S. Kathleen, Uhen, Mark D. (2018.  A cranial correlate of body mass in proboscideansZoological Journal of the Linnean Society, Volume 184, Issue 3, 20 October 2018, Pages 919–931, https://doi.org/10.1093/zoolinnean/zlx108
  4. Jukar, Advait M., Patnaik, Rajeev, Chauhan, Parth R., Li, Hong-Chun, Lin, Jih-Pai (2019). The youngest occurrence of Hexaprotodon Falconer and Cautley, 1836 (Hippopotamidae, Mammalia) from South Asia with a discussion on its extinction, Quaternary International, January 2019, https://doi.org/10.1016/j.quaint.2019.01.005
  5. Jukar, Advait Mahesh, Sun, Boyang, Bernor, Raymond Louis, (2018). The first occurrence of Plesiohipparion huangheense (Qiu, Huang & Guo, 1987) (Equidae, Hipparionini) from the late Pliocene of India,  Bollettino della Società Paleontologica Italiana; 57(2):125-132 · August 2018
  6. Saegusa H. (1996). Stegodontidae: Evolutionary Relationships. In:  Shoshani J, Tassy P. The Proboscidea : evolution and palaeoecology of elephants and their relatives, Oxford: Oxford University Press, xxii – xxv

 

It was a GREAT pleasure and honor speaking with Dr. Advait Jukar.  Many, many thanks for your time, Advait, your help, your fascinating insight and your gorgeous images!! I cannot wait to read your future scientific papers!

 

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Meet Dr. Katy Smith – Mastodon Detective

If you imagine the Great Lakes region over 10,000 years ago, you might see large, hairy beasts with relatively straight tusks grazing around boggy areas or moving within dense forests.  Their fur and overall appearance might cause you to confuse them with woolly mammoths, but these are the mammoths’ shorter, stockier cousins.  And if any of them would let you get close enough to inspect their mouths, you’d see in an instant that their teeth are completely different than those of mammoths.

 

[image of contemporary boggy area in Alaska, courtesy Getty Images]

 

Whereas mammoths are believed to have eaten grasses and even flowers, mastodons needed teeth suited to the mastication of hardier stuff: shrubs, parts of trees, perhaps pinecones?   Mastodon teeth, with the bumps and ridges one might associate with carnivores, are easily recognizable as ‘teeth.’  Mammoths, in contrast, needed to grind food, producing teeth with spherical lengths of ridges across each tooth.

ISM - Mastodon tooth

 

[image courtesy of Ron Richards, Indiana State Museum, for this post: Mammoths and Mastodons in Indiana – Part 1.  Can you tell which tooth belongs to which species?]

 

ISM - Mammoth tooth

 

[image courtesy of Ron Richards, Indiana State Museum, for this post: Mammoths and Mastodons in Indiana – Part 1.]

And while woolly mammoths pervade popular culture and interest, there are some, like Dr. Katy Smith, Associate Professor of Geology at Georgia Southern University and Curator of the Georgia Southern Museum, who prefer their lesser-known cousins and have made fascinating contributions to our understanding of them.

Mastodon discoveries usually produce the fossils of a single animal, and rarely a complete skeleton. Rarer still, finding skeletal remains of multiple mastodons at the same site.

Such a unique discovery occurred in 2005, when more than 300 fossils were found in Hebron, Indiana.  Now known as the “Bothwell site,” it was originally going to be the location of the landowner’s pond.  Instead, Indiana State Museum paleobiologist Ron Richards and his crew uncovered bones that included numerous mastodons (Mammut americanum), giant beaver (Castoroides) and hoofed animals with even-toes (artiodactyls).

ISM - 2005 Bothwell Mastodon 2

 

ISM - 2005 Bothwell Mastodon 1

[images of the Bothwell site dig, courtesy of Ron Richards, Indiana State Museum, for this post: Mammoths and Mastodons in Indiana – Part 2.]

 

Four years later, the Bothwell site became the focus of Katy Smith, her dissertation, and two subsequent papers she co-wrote with Dr. Daniel Fisher at the University of Michigan.

But let’s take a moment to consider what paleontologists uncover. However rudimentary this may seem, it is important to note that bones are generally not discovered in neat order, intact and with each skeletal component attached where it would have been in the life of the animal.

Consider, too, that not all bones survive.  And those that do are often broken or in terrible condition.

So even at a site such as Bothwell, which produced lots of fossils, a paleontologist’s job is no less challenging.  The pieces of information are incomplete, mere clues to the animals that died there.

The questions, however, are profuse.

Why were so many animals found in that one spot?

If, as it is currently debated, mastodons shared behavioral traits with modern-day elephants, was this a family unit?

If so, was this group—like elephants–comprised largely of female and juvenile mastodons?

And why were other unrelated animals discovered among them?

Did a sudden disaster kill them all?  Were humans involved?

 

Embed from Getty Images

 

Sexual dimorphism is another way of referring to the traits that make an animal either female or male.  Some of us would assume, since mastodon pelvic bones were not among the Bothwell fossil assemblage, that the sex of these animals would remain unknown.

There were 13 mastodon tusks, only four of which were complete. And this, remarkably, is what prompted Katy Smith’s research.

“I wanted to know if I just had tusks, what can I do to figure out if I’m looking at a male or a female,” she explained by phone.

Katy Smith - measuring an African elephant tusk

 

[image of Dr. Katy Smith measuring an African elephant tusk in (what this author believes must be one of the greatest places on earth) the basement and fossil collection of the University of Michigan; courtesy of Dr. Katy Smith]

 

“Other people have looked at [sexual dimorphism], but I wanted to look at it specifically with the Bothwell mastodons, because they were inferred to be female, and female mastodons are less common in the fossil record than males.

“When I presented preliminary results from my research in a paleontology class, the professor said, ‘Why don’t you try multivariate analysis?’ And it just kind of spiraled from there.”

Multivariate analysis,’ as the name implies, means using more than one type of measurement or observation towards a hypothesis.  In other words, rather than simply using size as a determination of sexual dimorphism, applying numerous methods and statistics that support or disprove it.

Already, the amount of information scientists have pulled from tusks alone is fascinating.

Tusks are teeth.  They are described, in Dr. Smith’s dissertation as “hypertrophic incisors.” And, unlike human teeth, they continue to grow the entire life of the animal. So where we can simply look at a human tooth and know immediately whether it is from an adult or a child, the same cannot be done with tusks.

What their hardy structure records includes the age of the animal, growth in winter or summer months each year, their overall diet, and periods of nutritional stress.  (As described in an earlier post, Proboscidean molars can even provide details regarding where they roamed during life.)

But much of this information can only be gleaned from well-preserved, intact tusks, as well as from cutting into and examining their chemical composition.

“If you don’t know what the sex of the animal is before you look at tusk microstructure,” she said, “it can be hard to interpret what you’re looking at.”

Part of what Dr. Smith hoped to discover were similarities in the tusks where sex and age had already been determined.  If certain structural elements were the same across female mastodon tusks, such that they tended to differ from male mastodon tusks, this might help determine sexual dimorphism in future tusk discoveries.

She also hoped to discover any similarities between the tusks of extant elephants and mastodons.

Katy Smith -longitudinally bisected tusk

 

[image of longitudinally bisected tusk, courtesy of Dr. Katy Smith] 

 

Thus, she studied and measured tusks of both species from numerous museum collections. (Asian elephant tusks were not used, as female elephants of this species tend to have either tiny tusks or no tusks at all.)  She rather amusingly refers to the approximate amount of tusks involved as “5,000 pounds of tusk.”

Her dissertation and the two papers describe the type of analysis performed in detail.  Among them were canonical variates analysis (CVA) and discriminant function analysis (DFA).

“Fortunately, we didn’t have to cut into the tusks to do those measurements. You just insert a stiff wire into the pulp cavity.”

“We think about tusks sometimes as stacks of sugar cones, because they actually grow in a kind of [layered] cone structure. So you think about one sugar cone, and then you put another one inside that one and then another one inside that one and so on and so forth. And the last sugar cone is empty. There’s nothing in it. That represents the pulp cavity.”

“[Analyzing the] pulp cavity is probably one of the best single measurements that you can use to distinguish between male and females. [I]n females, that pulp cavity will terminate before the gum line, and in males, it will terminate after the gum line, closer to the tip.

“This is something that we saw in almost every mastodon. So it was kind of cool.”

 

Katy Smith - female mastodon

 

[image of female mastodon skull and tusks, courtesy of Dr. Katy Smith]

 

“If we could have cut every tusk, I would have,” she admitted, and laughed. “But it was a matter of collecting these measurements at different museums. And so I would just go there and collect all of them, and that was how we’d get the pulp cavity depth.”

“I’ve always been interested in paleontology,” she said when I asked her how she got started.

“I’m one of those kids who just never grew out of it. My parents used to take me to the museum all the time, and I used to spend hours and hours staring at the dinosaur dioramas there, just loving it.  I told my kindergarten teacher I wanted to be a paleontologist. I never changed! My 5-year-old self grew up and became a paleontologist.”

But her interests moved away from dinosaurs when she realized that their fossil record in Wisconsin, her home state, was rare to nonexistent.

After all, she said, “I started just wanting to explore what was underneath my feet.”

It wasn’t until grad school at Michigan State, where she met the late Dr. Alan Holman, that she realized her passion for mastodons.  His own interest in the species was infectious, and it was through him that she learned of the numerous mastodon (Mammut americanum) fossil discoveries in the area.

“Wow!” she said, recalling her initial reaction. “There are over 300 mastodons in Michigan. This is exciting!”

Katy Smith - male mastodon

[image of male mastodon skull and tusks, courtesy of Dr. Katy Smith]

Not surprisingly, she did her PhD work at the University of Michigan, home to Proboscidean expert Dr. Daniel Fisher, who was her advisor.

“I wanted to work with him,” she explained, “because I wanted to continue working on mastodons, and he had a couple of ideas for projects. One of them included this assemblage of mastodons from Indiana, which were—supposedly—all female.”

What she discovered regarding the Bothwell site is both thought-provoking and fascinating:

  • 8 tusks were determined to be female; the other 5 are unknown
  • the ages of the mastodons range between 19 and 31 years old
  • there is evidence that at least one juvenile might have been among them (a “juvenile tooth crown” was found)
  • given that two mastodons died in winter, and another two died either in late summer or early autumn, this indicates that the collective deaths of these animals didn’t happen at the same time (hence, not a single event)
  • none of the mastodons appeared to be under nutritional stress when they died
  • members of a family unit would be expected to have the same “isotope profiles”–chemical signatures in their teeth–but these do not

Based on the evidence provided, Dr. Smith wonders whether these animals were part of a meat cache for humans (members of the Clovis culture) that co-existed at that time.

But perhaps the single most remarkable result of her research is helping other paleontologists–who often have nothing more than a single tusk–determine the sex of that animal using her different types of analysis.

Prior to her dissertation, only one female mastodon tusk had been analyzed for growth rate.  To date, I am unaware of any other publication (paper or book) that helps detail the sexual dimorphism in mastodons by tusks alone.

When I remarked upon this, I asked her if others had cited her work.  Her response, after stating that others had, was equally fascinating to me.

“It’s always the hope as a scientist that you’re contributing in some way,” she said, “and you know that you’re contributing if somebody else is using what you’ve done.”

 

An enormous and sincere THANK YOU to Dr. Katy Smith for her generous and fascinating answers to my many questions, her gracious help when I had trouble understanding certain points, and for being so much fun with whom to connect! I cannot express how much I wish I could attend her classes, nor how fascinating I found her dissertation. I am profoundly grateful that she shared it with me!

A sincere thank you to my Dad, as well, for helping me understand tooth components (i.e.: dentin, cementum)!

**A quick reminder that I am neither a scientist nor a paleontologist, so any errors in this post are my own.

Bothwell Mastodont Dig, courtesy of Indiana State Museum; many thanks to Bruce Williams and Leslie Lorance!

—————

References:

 

Other references:

 

Cohoes mastodon size comparison

[image of sign in the NY State Museum illustrating the size difference between an extant elephant, a woolly mammoth and the Cohoes mastodon; picture taken by the author]

The Treasure in Gold Mines: Fossils! – Yukon Paleontology, Part 2

I admit to having preconceived notions of what it means to find fossils and to mine for gold.  It never occurred to me that these two occupations might be interconnected.  Nor would I have ever described the image below as what it actually is: placer gold mining.

Placer Gold Mining - Monitor

 [image of a water monitor, placer gold mine in Quartz Creek, courtesy of the Government of Yukon. Can you find the rainbow?]

That water jet is called a ‘monitor’, and it slowly melts the permafrost, exposing the alluvial gold from the gravel below.

It also reveals fossils.

“Since the beginning of the Gold Rush, people have been finding Ice Age fossils there,” explained Dr. Grant Zazula by phone.

The Gold Rush, an event that peaked in 1898, brought people from all over the world to the Klondike area of the Yukon.  It was once solely the home of several indigenous cultures, including the Inuit, Han, Tagish, Tlingit and Tutchone. But the hope of finding treasure—in an industry that required inexpensive equipment (a pan, a rock pick)—brought thousands to an area that most would consider inhospitable.

 

 

Embed from Getty Images

 

gold miner Gerry Anhert

[image of gold miner, Gerry Ahnert, courtesy of the Government of Yukon]

One of the techniques used to find gold at that time was borrowed from California mining: water monitors.  Monitors were also relatively inexpensive and highly effective.

Back then, as now, these monitors revealed not only gold, but a wealth of fossils.

Assistant Palaeontologist Elizabeth Hall organizing a days collection of bones in the tent at our field camp near Dawson city

[image of Paleontologist Elizabeth Hall organizing a day’s collection of bones at the field camp near Dawson City, courtesy of the Government of Yukon]

“I’m always pretty fascinated by these stories immediately post-Gold Rush of people finding mammoth skulls,” said Dr. Zazula.

One can see a number of black-and-white images of these and other fossil finds in Ice Age Klondike, written by Dr. Zazula and Duane Froese.  Finds such as this prompted museums to send representatives out to the region to bring back fossils for their collections. One such expedition in 1907 and 1908 is detailed in the Bulletin of the American Museum of Natural History in NY.

“Without the gold mining, these fossils would never be found,” Dr. Zazula continued, referring to today’s fossil discoveries. “They’re using heavy equipment and other types of equipment to move this frozen ground because [it] is essentially locked in permafrost that wouldn’t be accessible without the gold mining.”

Upper section

Looking upstream at 2011 stripping operation

Unsampled tehpra (inaccessible) visible in wall of monitoring drain

TK-11-03TK-11-06

QCreek mine - LOVE THIS - monitor and permafrost - DawsonFieldwork_2011_TKuhn_029

 [images of gold mines near Dawson City, courtesy of the Government of Yukon]

Melting the frozen ground with these jets isn’t as damaging to fossils as one might imagine. Dr. Zazula described a process in which fossils are slowly removed from the heights of the muck—the frozen silt—and slide down into the valleys below.  When remarkable fossils are seen by paleontologists, the miners always accommodate them, enabling Dr. Zazula and his colleagues to excavate them manually.

Arctic Ground Squirrel fossil skull

 [fossil Arctic Ground Squirrel skull emerging from the muck, image courtesy of the Government of Yukon]

Zazula sampling squirrel nest

[Dr. Grant Zazula sampling frozen sediment along a vast wall of muck at Quartz Creek, courtesy of the Government of Yukon]

 

It’s an incredible partnership, one that began in the 1960’s with Dr. Richard Harington of the Canadian Museum of Nature. Dr. Harington made annual summer trips to visit the miners and discuss their fossil finds.  It is a tradition that Dr. Zazula and the other two Yukon paleontologists before him have maintained.

But consider the expanse of the Yukon Territory.

Land near Dawson City

[image of land near Dawson City, courtesy of the Government of Yukon]

And consider that, as Dr. Zazula stated, “[t]here are 100 active gold mines, give or take a few dozen here or there. And virtually all of them produce Ice Age fossils.  So in a summer, we can collect 5,000 specimens. There’s a lot of material coming out of the ground, and we’re trying to recover it as much of it as we can. It’s almost industrial-scale paleontology.”

This gave me pause: one Yukon paleontologist in the entire Territory, who—in addition to keeping in touch with about 100 mines in the Klondike—is responsible for all of the other fossil discoveries and research of the area.

“Prior to 3 years ago, it was really a one-person operation and that was me,” he admitted.

With the acquisition of funds, however, Dr. Zazula now has two assistants in the field: Elizabeth Hall and Susan Hewitson.

Elizabeth, Dick, and Susan with fossil Bootherium skull

[image of Elizabeth Hall, Dick Mol holding a fossil Bootherium skull, and Susan Hewitson, courtesy of the Government of Yukon]

They have established a field camp near Dawson City in close proximity to the gold mines. This enables them to be in daily contact with the miners in the short mining season—the end of May through October.  Dr. Zazula described this work as driving on back roads to the various mines, getting to know the miners and collecting the fossils released from the permafrost.

Elizabeth Hall recording a collection of bones at a gold mine

 

[image of Elizabeth Hall recording bones at a gold mine, courtesy of the Government of Yukon]

“Since we’ve done that, our collection has just exploded in terms of the quantity of material that we’re finding.  But it also really establishes and strengthens the relationships that we have made with the gold miners as well.”

Dawson City

 [Dawson City, the previous capital of the Yukon Territory until 1953; At the height of the Gold Rush, this town consisted of numerous wooden buildings and a sea of canvas tents behind them; image courtesy of the Government of Yukon]

“[The] program really hinges on [these] two people,” Dr. Zazula wrote. “Elizabeth Hall oversees most of the field work in the Klondike and is the collections manager, and Susan Hewitson [is] a field technician in the summer months.

“They do most of the work to collect the fossils, clean the fossils, identify the fossils, catalog the fossils and organize the database. This really frees up my time to write, do research and other outreach work.”

Elizabeth Hall holding baby mammoth

[image of Elizabeth Hall holding a baby mammoth tooth, courtesy of the Government of Yukon]

Elizabeth, Susan and her husband Alex collecting bones in 2012

[image of Elizabeth Hall, Susan Hewitson and her husband collecting fossils, courtesy of the Government of Yukon]

 

“Elizabeth started her as a summer student assistant about 10 years ago, and we finally created a full time position for her 3 years ago. We were also students together at Simon Fraser University. She is in the middle of completing a masters degree in Earth and Atmospheric Sciences at University of Alberta; her thesis work is on fossil microtine rodents from Old Crow, Yukon.”

Elizabeth Hall in field

[image of Elizabeth Hall, courtesy of the Government of Yukon]

“When it’s good for gold, it’s a good time to be an Ice Age paleontologist in the Yukon because there’s so much material that’s coming out of the ground.”

Tyler Kuhn

 [Paleontologist Tyler Kuhn with a mammoth tusk found at a placer mine in Dawson City, Yukon; courtesy of the Government of Yukon]

 

Again, an enormous thank you to Dr. Grant Zazula for his fascinating insight and most generous time.  

Thank you, again, to Dick Mol.  

And thank you to all of the gold miners who enable Dr. Zazula, Elizabeth Hall and Susan Hewitson to conduct their research and collect fossils!!

Dick Mol and Grant Zazula - Yukon

[image of Grant Zazula and Dick Mol, holding a steppe bison skull; taken by Florian Breier, courtesy of Dick Mol]

———————

Yukon Paleontology Program: http://www.tc.gov.yk.ca/palaeontology.html

Yukon Beringia Interpretive Centre: http://www.beringia.com/

Publications and articles referenced:

Exciting New Info About Mastodons and Humans – Yukon Paleontology, Part 1

“Good morning!”

It’s not just a greeting; it sounds like a proclamation.

The voice on the other end of the phone is deep, melodic, and—as our conversation progresses—punctuated with moments of laughter.  We have been discussing paleontology in the Yukon, and with each new detail, I begin to wonder why this territory is not making regular international headlines.

Dr. Grant Zazula’s work is fascinating, and it is neither a short phone call nor the only communication we’ve exchanged. And yet, it is all that I can do not to encourage him to keep going, long after social decorum dictates that he has been more than generous with his time.

Dr. Zazula and mastodon leg

[image of Dr. Grant Zazula with a mastodon ulna, part of the Earl Bennett mastodon, courtesy of the Government of Yukon]

Dr. Zazula is the Yukon paleontologist, a job that has only existed since 1996. His own tenure began in 2006.  With an office in Whitehorse, the capital of the territory, his work oversees an expanse of Canada that abuts Alaska.  It is a land of dramatic beauty, where colors dance in the sky and mountains tower in silent grandeur.

Embed from Getty Images

His most recent paper, co-written with 14 other people, made news throughout the world and continues to attract media attention. In it, the scientists present data that completely overturns previously believed information about extinct animals and the impact that humans may or may not have had upon their survival.

“[T]here were two radiocarbon dates in the literature from Yukon mastodons,” he explained in an email. “One that was ~18,000 and the other 24,000 years old.”

“Based on analysis of the paleoecology, that was a time when steppe-tundra grasslands covered Alaska, Yukon and Beringia. There were probably no trees, few shrubs and almost no standing water. It was very cold and, especially, dry. This seemingly is not good mastodon habitat. So either the dates were incorrect, or our understanding of mastodon ecology, behavior and adaptations need[s] to be revised.”

Various species of mastodon once existed throughout the world.  Although their fossils look elephantine, they are not believed to be direct ancestors of today’s elephants. They are, however, part of the same umbrella mammalian group: the Proboscidea (so-named for the trunks possessed by many—but not all–of their members).  In North America, that group contained the American mastodon (Mammut americanum), the woolly mammoth (Mammuthus primigenius), and the Columbian mammoth (Mammuthus columbi).

Cohoes mastodon

 [image of the Cohoes mastodon, NY State Museum, Albany; taken by the author]

Mastodons tended to have straighter tusks and were shorter than their mammoth cousins. They also ate hardier vegetation, food that required a much different tooth structure than mammoths.

ISM - Mastodon tooth

[image of mastodon tooth, courtesy of the Indiana State Museum]

ISM - Mammoth tooth

[image of mammoth tooth, courtesy of the Indiana State Museum; for more info about the differences between mammoths and mastodons, see this post.]

Parts of Siberia, Alaska and the Yukon were once connected in an area known as “Beringia.”  The Bering Strait did not yet exist, enabling animals and eventually the first humans to cross into our continent.  It is believed that humans arrived in what is now North America about 14,000 years ago.

And this is where the research of Dr. Zazula and his colleagues becomes particularly important.

Prior to their paper, one theory to mastodon extinction laid the blame upon first humans: it was proposed that they overhunted these animals.

Sampling 36 fossils and presenting 53 new radiocarbon dates, Dr. Zazula and his colleagues found that mastodons within Alaska and the Yukon were much, much older than the originally published dates.  In other words, their research suggests that mastodons from what was once Eastern Beringia were no longer present when the first humans appeared.

The path to this remarkable research did not happen overnight.

The foundation appears to have been laid by two different events: by the chance meeting of Dr. Zazula and a gold miner, and later, by the PhD work of a graduate student.

If one reads the acknowledgements on the aforementioned paper, Dr. Zazula references Earl Bennett as both the donor of a partial mastodon skeleton and his inspiration to learn more about mastodons within the Yukon.

“Earl is a great Yukoner,” Dr. Zazula wrote when asked about this. “He mined for gold underground in the winters with a pick and shovel, decades ago. He worked on big gold dredge machines. And, he loves paleontology.

“While mining, he made collections of Ice Age bones that were just left around the mining camp or were encountered while mining. He eventually amassed an amazing collection.

“In the early 1970’s a gold dredge on Bonanza Creek hit a skeleton of a mastodon. An incredibly rare find! Someone collected it and was looking to sell it. So, Earl bought the skeleton just to make sure that it never left the Yukon. He had it in his garage for decades.

“One day a mutual friend introduced me to him in a coffee shop, about a year after starting my job [as the Yukon paleontologist]. He said that he had a mastodon skeleton and wanted me to see it. I ‘corrected’ him, saying that it was more likely a mammoth, because we almost never find mastodons in the Yukon. He assured me he know the difference and said he would see me tomorrow at my office.

“The next day he backed his truck up and in it was a partial mastodon skeleton. I couldn’t believe it. There were several postcranial bones, some vertebra, scapula, parts of the skull and parts of the mandible with teeth. It was amazing. I wanted to find out how old it was, and that was one of the inspirations for this project. Earl is a good friend now and big supporter of our research.”

Bennett mastodon skeleton

[Paleontologist Grant Zazula with a partial American mastodon (Mammut Americanum) skeleton found on Bonanza Creek and donated to the Yukon fossil collection by Earl Bennett, from Ice Age Klondike, courtesy of the Government of Yukon]

That partial skeleton was indeed one of the many fossils sampled for the paper.

Dr. Jessica Metcalfe, one of the co-authors, also prompted this research when conducting work for her PhD.

“[S]he was doing a project looking at stable isotope ecology of mammoths and mastodons in various places in North America,” said Dr. Zazula.

Jessica Metcalfe with mammoth bone

[image of Dr. Jessica Metcalfe with mammoth bone, courtesy of the Government of Yukon]

Her work included Yukon fossils that were sent to the lab at the University of Arizona to be radiocarbon dated.   Those dates turned out to be older then 50,000 years old.

“So that’s what got me thinking,” he continued, “‘well, maybe those original published dates are wrong.’”

“The first step was to re-date [the specimens that had produced the original published dates]. The new dates turned out to be >50,000 years. So we knew there was a problem with the previous dates. We figured then we should date as many as we could get our hands on.”

This lead Dr. Zazula to connect with Dr. Ross McPhee, another co-author.

“I got in touch with him early because he oversees collections at the American Museum of Natural History, [and] he has a big interest and lots of experience working on Ice Age extinctions. [H]e’s an excellent writer and really kind of kept us going with some of the writings. He was really integral to keeping things together.”

The paper eventually involved a total of 15 people.

“I feel pretty strongly that if you worked on it and contributed to it, then you should be considered an author,” Dr. Zazula stated.  “So it ended up being a long list.”

One of the first aspects their paper addresses is the reason behind why the original published dates are incorrect: the dating analyses were contaminated by fossil conservation methods.

“Humic acids in soils can be absorbed by the bones and teeth and chemically bind themselves to the collagen,” he wrote, explaining further. “So, modern ‘young’ carbon in those acids basically contaminates the ‘old’ collagen in the ancient fossil. And, it can be tricky to remove.

“The same with consolidants in museums. Varnish, glue, and other substances to preserve fossils can be absorbed into the bone and chemically bind with the collagen in the bone. These substances probably contain young, modern carbon which messes up the radiocarbon dating measurements.”

When asked whether museums continue to use the same preservation products that contaminated the dates, he wrote, “Yes, for sure. The thing is now museums keep better records of what they use. Many of the fossils we dated were collected in the 1940’s or at least several decades ago. Museums were not that vigilant about keeping detailed records on those things then. Also, they seemed to put preservatives on everything. Now, at least if we know what was put on it, the chemistry can by developed to remove it. Most of the common preservatives now are soluble in alcohol or acetone and can be dealt with. The problem is when they are unknown.”

We discussed this further by phone.

“One thing about Alaska and the Yukon,” he said, “is that the Ice Age bones that come out of the ground are so well preserved because of the permafrost. In other localities, say, the deserts of the American Southwest or the Great Basin or the Plains, where bones have been out in the sun and [are] dry and hot, they [sometimes] fall apart really easily when they come out of the ground. They need to be glued and consolidated with these various types of museum products.

“So you kind of have to weigh the different values.

“Say if it’s a specimen that’s already been radiocarbon dated, and it starts to slowly disintegrate, well, then you kind of have to intervene or else you’re just going to end up with a box of dust and broken bone. You have to decide whether the importance is more with display or preservation of the morphology versus needing to radiocarbon date or other types of analysis.

“[Y]ou have to look at the pro’s and con’s of whether the sampling [for radiocarbon dating] will ruin the specimen or not, and what is the potential information that can be gained by doing it. To me, I feel that having a research collection [in the Yukon], it’s all about research and learning new things from these specimens.”

Ultimately, I wondered whether Dr. Zazula expected the results he and his colleagues uncovered.

“I wasn’t quite sure,” he answered. “I had the gut feeling that these previously published radiocarbon dates were probably wrong. It didn’t make a lot of sense ecologically to have mastodons living in the far North when it was seemingly habitat they couldn’t live in: habitat with grassland and cold, dry steppe tundra conditions, no trees and very few shrubs.

“But there [was] also a part in the back of my mind that thought, ‘well, if those [previously published dates] were right, that’s maybe even more interesting because they are telling us something about mastodons and their behavior and their adaptations that we didn’t know before.’”

————

It was a great honor and pleasure to connect with Dr. Grant Zazula! Not only patient with my myriad questions, he is an adept and fascinating ambassador for the Yukon. A Mammuthus columbi-sized thank you to him!

A Mammuthus columbi-sized thank you to Dick Mol, as well, who is the reason behind this post!

Dick Mol with horse skull

[image of Dick Mol with fossil horse skull, found near Dawson City, Yukon; courtesy of the Government of Yukon]

Yukon Paleontology Program: http://www.tc.gov.yk.ca/palaeontology.html

Articles and publication referenced:

 

Listen to Dr. Zazula discuss his paper on the CBC’s Quirks & Quarks: http://www.cbc.ca/radio/quirks/quirks-quarks-for-dec-6-2014-1.2864605/mastodons-made-an-early-exit-from-the-north-1.2864634

 

Paleontologist Spotlight: Dr. Penélope Cruzado Caballero – Hadrosaurs!

Hadrosaurs are commonly referred to as “duck-billed dinosaurs.” An herbivore that once roamed Europe, Asia and North America, this particular species of dinosaur has provided exciting finds in the form of “dinosaur mummies”.

The “Trachodon mummy”, discovered in 1908 in Wyoming, now resides in the American Museum of Natural History.   This provided skin impressions in the rock surrounding the fossil.

Dakota”, found in North Dakota in 1999, provided actual skin, tendons and ligaments.

There are currently two subfamilies of hadrosauridslambeosaurine and saurolophine (previously known as hadrosaurine).  Their differences lie in the hollow crest of the former; the lack thereof of the latter.

Hadrosaurs were the first dinosaur that Dr. Penélope Cruzado Caballero discovered in her fossil digs.

“I love them,” she writes.

Dr. Cruzado Caballero works both in Argentina and in Spain. In Argentina, she is a researcher at CONICET (Consejo Nacional de Investigaciones Científicas y Técnicas).  She is a professor at the  Paleobiology and Geology Research Institute (Instituto de Investigación en Paleobiología y Geología) at the National University of Rio Negro. In Spain, she is also a member of the Aragosaurus Group, a research group affiliated with the University of Zaragoza.

She has written extensively on hadrosaurs.  Despite her very busy schedule that included traveling between continents, she very graciously responded to my questions below.

Dra. Penélope Cruzado Caballero y Dr. José Ignacio Canudo

(Image courtesy of Dr. Penélope Cruzado Caballero; Dr. José Ignacio Canudo and Dr. Penélope Cruzado Caballero with Blasisaurus canudoi* fossils–a new species described by Dr. Cruzado Caballero, Dr. José Ignacio Canudo, and Xabier Pereda-Superbiola in 2010.  The species name “canudoi” is in honor of Dr. José Ignacio Canudo.)

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1. How long have you been a paleontologist?

I started research as a student in 2004, but I became an official paleontologist in 2012 when I finished my thesis.

2. Where have you dug for fossils?

Fundamentally, I have dug in several places in Spain (Burgos, Cuenca, Huesca, Lérida, Teruel and Zaragoza), but I have also dug in France (Esperaza) and am now digging in Argentina (Las Lajas).

3. Have you discovered any new species in your work?

Yes. During my thesis, I had the opportunity of discovering a new species of crocodile (Allodaposuchus subjuniperus),  and I have participated in the discoveries of a possible new ornithopod and a possible new sirenid.

4.  From your articles, it looks like your work focuses on Hadrosauridae and Lambeosaurinae. Is this correct?

Yes, my thesis doctoral was about the hadrosaurs’ remains from Huesca (Spain).

5. What interests you about this group of dinosaurs?

Hadrosaurs were my first introduction into the world of dinosaurs, and I like their paleontology. I love them.

6. Do you work with scientists from all over the world? If so, from what countries and on what projects?

Currently, I collaborate with Argentinian and Spanish scientists to study hadrosaur relations and behavior in Europe and South America.

7. What types of fossils are found in Spain?

In the Aragosaurus Group, I have had the opportunity to find and dig every type of vertebrate within the Mesozoic era and Paleogene period.

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Dr. Cruzado Caballero’s articles: http://scholar.google.com/citations?sortby=pubdate&hl=en&user=XoIYrhkAAAAJ&view_op=list_works

The Aragosaurus Group at the University of Zaragoza, Spain: http://www.aragosaurus.com/

Instituto de Investigación en Paleobiología y Geología, at the Universidad Nacional de Río Negro, Argentina: http://investigacion.unrn.edu.ar/index.php/institutos

Featured articles co-written by Dr. Cruzado Caballero:

A New Crocodile from the Upper Maastrichtian of Spain: Implications for the Initial Radiation of Crocodylids, Plos One

New material and phylogenetic position of Arenysaurus ardevoli, alambeosaurine dinosaur from the Late Maastrichtian of Arén (North Spain), Journal of Vertebrate Paleontology

La Cantalera: an exceptional window onto thevertebrate biodiversity of the Hauterivian-Barremian transition in the Iberian Peninsula, Journal of Iberian Geology

*Blasisaurus canudoi gen. et sp. nov., a new lambeosaurine dinosaur (Hadrosauridae) from the Latest Cretaceous of Arén (Huesca, Spain), Canadian Journal of Earth Sciences

I’d like to extend an Argentinosaurus huinculensis-sized THANK YOU to Dr. Penélope Cruzado Caballero for taking the time to answer my questions despite her busy schedule, and for her generous and fun responses to my emails! What a great pleasure! 

¡Muchas, muchas gracias!