Monday, September 13, 2021

Interview with Paleontologist: Rhiannon LaVine

Rhiannon (Rhi) LaVine is an invertebrate paleontologist who is an NIH-IRACDA postdoctoral fellow in the Biodiversity Institute at the University of Kansas. Her research interests revolve around questions relating to the mechanisms that generate and influence patterns of morphological diversity in organisms and how that shapes their evolutionary trajectories. She is particularly interested in exploring this topic using fossil arthropods such as trilobites and trilobite-like animals. Rhi received her Ph.D. from the University in Chicago where she began this line of research using agnostine arthropods. Prior to graduate school, she received her B.S. from the University of Wisconsin - Whitewater where she investigated the response of gastropod faunas to the end-Permian mass extinction both in her undergraduate research and through the Natural History Research Experiences (NHRE) internship program hosted at the National Museum of Natural History, Smithsonian Institution in Washington D.C.


Rhi with an assortment of fossils

Question 1: What was your earliest sign of interest in paleontology that you can remember?


RV: Doesn’t everyone around my age say, “Jurassic Park”? I hate to say that I’m not much different in that respect. Before the film was released, my late father read the book and shared it with me when I was around 7 or 8 years old. He was also a substitute teacher at the time and (hilariously) read passages of it to some of his classes---namely the gruesome Nedry vs. dilophosaur scene, which was our favorite. It was one of the many things over which my dad and I bonded, and following the film’s release (which we saw in theaters), I had my big ol’ dinosaur phase that just about every kid goes through. That led to a deeper interest in fossils and geology which, unfortunately, became somewhat stifled as I became more recognized for my artistic talents instead of my academic interests. Thankfully I was in the right place at the right time in college to have that passion reignited.

 

Question 2: Did you have anyone who served as a role model when you were younger?  Do you still have any now?


RV: I am my father’s daughter and have always looked up to him. He was someone who never hesitated to chase his dreams (even the ridiculous ones that took him out to LA to be a drummer) and stand up for what was right. He was a much-loved high school teacher who served as inspiration to many and a kind ear to all. I’ve always said that if I end up being half as good of an educator as he was, my career will have been successful.

More recently I have been lucky enough to learn quite a bit from Sue Kidwell, whose career of pioneering work has really shaped how we address and ask questions of the fossil record. I can honestly say that she is an inspiration, especially when it comes to maintaining the drive to continue pushing against the status quo in our field.


Question 3: You primarily work with invertebrates.  Tell us more about your work and what it's all about. 

RV: The first thing that I was asked in grad school was “what’s your question?”, which was a not-so-subtle hint that I should divorce myself from focusing on a particular study organism and think about questions that could be applied broadly. That being said, my work gets at questions relating to how patterns of morphological diversity are generated. Heritable variation is the raw material upon which natural selection acts, after all. I’m interested in figuring out what causes that variation and how, if at all, it scales up to trends that we see at the macroevolutionary level. I tackle this using geometric morphometric methods, meaning that I rely on shape data. As for the system, it just so happens that marine invertebrate fossils, specifically arthropods, are ideal because they preserve very well (often minimally-distorted) and there are a lot of them (allowing for good sample sizes). As an example of the sort of work that I like to do, for my dissertation I worked with agnostine arthropods, which are tiny, blind, trilobite-like critters. I measured them in a way that would reveal developmental constraints on their form, which could indicate long-term constraints on morphological diversity in this group of organisms as a whole. The current work that I’m doing in my postdoctoral position doesn’t get at the generation aspect of variation, but instead explores the extent of morphological variation in a group of trilobites and how it manifests phylogenetically, biogeographically, and through time.


Left: an agnostine arthropod cephalon (head) mounted on the tip of a toothpick. Right: Landmark and semilandmark configuration for geometric morphometric analyses.

Question 4: Was there anything you did or learned as you were on your way to your current career that you feel got you to where you are?  What sort of field experience, a class, networking with the right people, or possibly something different?

RV: I would say that networking and early research experience were the key elements. I often talk to prospective undergraduates who are worried that if they don’t go to a big name school, their hopes and dreams of becoming a paleontologist will be dashed. Well, here I am with my start in a relatively small undergraduate institution and I somehow stumbled upon this career. I firmly believe that I got to where I am because my undergraduate advisor pushed me to network and get involved in research early on. I went to and presented at GSA and other conferences, talked with other students in my field, reached out to potential advisors, and I was generally enthusiastic and active in the geoscience community. I feel as though if I did go to a bigger school for my undergraduate degree, I may have been just another face in the crowd. The fact that I did go to a small school provided me with the opportunity to receive more direct mentorship and guidance.

 

With colleague and “trilobite twin” Matt Witte at GSA

Question 5: What would your advice be to anyone trying to make a career in paleontology (or science in general)

RV: Get involved in research as soon as you’re able to do so. Even if you’re in high school, contact your local club to see if there are any outings that you can join. Reach out to paleontologists at a nearby museum or university to volunteer to help with their collections or, even better, see if they need someone to do some otherwise tedious fossil counting/measuring for a project. Get your hands dirty and make yourself visible to those who are in the field of study that you’re aiming to pursue.


Question 6: What was or is your favorite project so far? (geology or paleontology)

RV: My favorite project is not so much a project as it is a long-term endeavor that focuses on figuring out what’s going on in a particular unit called the Spence Shale: a middle Cambrian Lagerstätte on the border of Utah and Idaho. Not only does it contain a wide array of complex and, frankly, weird preservational environments, but it is bursting with such diverse and amazingly-preserved fossils, many of which remain undescribed. I started working on this unit near the beginning of my dissertation, specifically targeting the agnostoid fauna. Later on my colleague, Julien Kimmig, spearheaded the bulk of the work on this unit. Now, with help from L.J. Krumenacker (who we temporarily coaxed over from the vertebrate paleo side), we are hopefully beginning to put the pieces of the Spence puzzle together.


Rhi (center) with colleagues L.J. Krumenacker (left) and Julien Kimmig (right) after trenching the type section of the Spence Shale.

Question 7: Do you have a favorite destination when it comes to fossils?  Why?

RV: A a perfect continuation from the previous question: my favorite destination is Spence Gulch, the type section of the Spence Shale. It’s an idyllic little stream cut within a forest in Idaho. It’s quiet, scenic, and one can just spend the entire day easily splitting apart the rocks to find bountiful and beautiful fossils. This site really spoils you. I’m pretty certain that if it was someone’s first fossil-hunting site, it’d ruin them for any other site because the bar would be set so high. I’ve not encountered too many other places like it.


Views of Spence Gulch

Question 8: A popular image of paleontologists is that they are constantly out in the field digging up fossils, which is true sometimes  What people don’t realize is that a lot of paleontology work is conducted in a lab as well.  In your experience how much time have you spend in the lab and in the field?  What do you prefer?


RV: For me it’s about 10% fieldwork and 90% “in the lab”. Of course, “in the lab” means a lot of things: in the lab prepping/sorting fossils, rifling through museum collections, sitting behind a computer running analyses, doing literature reviews, etc. I wish I could justify more fieldwork in my research. There’s really nothing comparable to getting out there, cracking open a piece of shale, and finding something new that no one has ever laid eyes on. “Lab” work is the price I pay to be able to go out into the field from time to time.

 

Question 9: Are there any fossils you’d like to work with that you haven’t yet?


RV: I would love to work on insect fossils! Unfortunately I can’t think of too many questions that both pique my current interests and that the fossil record of insects can reasonably accommodate.

 

Question 10: Do you ever get criticized on any of your work?  How do you handle it?


RV: Don't we all? In my experience thus far, the vast majority of my colleagues are wonderful people who offer criticism in a helpful manner. I have encountered people who get possessive over their study system of choice and are on the lookout for anything to pick apart, though. I’d like to say that I handle it with the practiced grace of a respectable academic, but my inner (outer?) punk tends to get riled up. I usually end up taking a deep breath, stopping myself from being confrontational, and reminding myself that it comes with the territory.

 

Question 11: A common idea is that paleontology is just a “for fun” science, with no real impact or noticeable effect that helps the world.  Do you think paleontology has a bigger part to play to than this?  How?


RV: One of the main things that I try to drive home with all of my students (or even just people with a passing interest in what I do) is the absolute vastness of deep time, and I think that’s something that we can only begin to wrap our heads around via the study of paleontology. It’s easy for someone to rattle off numbers associated with absolute ages of the earth without actually understanding what that number means. It’s also pretty easy to look at all of the life forms that exist today and think that’s all we need to consider in order to understand the natural world.  By contrast, when you’re able to incorporate the fossil record, you’re able to begin to understand how life has emerged and changed over enormous spans of time, resulting in the mind-blowing diversity that we see today. Suddenly we’re able to start to piece together the puzzle of how modern biodiversity came to be within that structure of seemingly unfathomable vastness of time.


Collecting from Miners Hollow in the Wellsville Mountains

Question 12: Who was the first paleontologist you met?  How was that interaction?

RV: Rex Hanger, professor at the University of Wisconsin - Whitewater. At the time, I was an art major who was severely dissatisfied with my program and career path. As a lark, I took the Geology 204: Earth and Life History course because I’d always had an interest in geology and paleontology, but I never really saw myself as a STEM person. Rex made the subject incredibly accessible and thus I came to the realization that I could maybe pursue paleontology as a career. I approached him one day after class and told him that I was considering changing my major to geology. I will never forget the big smile on his face---of course, I probably would have grinned too if a weird, tattooed kid in a tattered Bauhaus shirt came up to me and asked me to be their advisor. From that moment on he became my mentor, immediately plugging me into a research project and setting me on the trajectory that led me to where I am now.

 

Question 13: What is your favorite prehistoric animal?  Was it different when you were younger?


RV: Oh dear, can I pick one from each phylum? I’m probably expected to pick a trilobite, so in that vein I’ll choose Zacanthoides typicalis. It’s a somewhat common trilobite found in my favored field site, but even so I always get excited when I find one. They’re so charismatic! I refer to this group of trilobites as “the punk rockers of the Cambrian trilobite world” for a reason. When I was a kid, I was into dinosaurs and, of course, I was enamored with the “velociraptors” from Jurassic Park. I wasn’t even really deterred when I found out that Velociraptor sp. was, by comparison, a puny little thing. I thought it was even cooler that it was a knee-high terror.

 

Question 14: If you could use a time machine to go back and pick only one prehistoric animal to bring back from history and observe alive and in person, which would it be and why?


RV: Opabinia regalis because, well, just look at that thing! What was it even doing?!

 

Opabinia regalis watercolor by Christopher DiPiazza

Question 15: Back to the time machine.  This time you can go back to any place and time period and have a look at what the environment was really like.  Which one would you pick and why?


RV: The ​Cambrian, of course! I may have a bit of a bias, but being able to see that comparatively alien world in action would be extraordinary


Question 16: Which is your favorite museum?  Why?

RV: I ​will always have a soft spot for the Field Museum of Natural History in Chicago. It was the first big museum that I ever visited. In fact, I found a picture of me as a kid with Bushman the Gorilla and recreated the picture over 30 years later before I left the city for my current position

The Evolving Planet exhibit is a wonderful walk through earth’s history. There were many days that I would visit it and space out to the soothing sounds of the Cambrian seascape.


Rhi and Bushman at the Field Museum, over 30 years in between.

Question 17: What hobbies do you have?  (Don’t have to be paleo-related.)


RV: I definitely make an effort to keep a work-life balance, which means that my hobbies are not related to paleontology. When the weather cooperates I get outdoors to go running or hiking; the latter of which usually involves me taking my camera along so I can dive into the underbrush and take photos of neat insects and such. I am also an avid curler (the sport, not the hairstyling). Beyond it just being great fun and challenging, I’ve met some of the coolest people in the curling community. It’s a sport with a foundation in good sportsmanship and camaraderie---I highly recommend that anyone who has ever had even a passing interest to try it out if they can. Finally, no shame: I’ll admit that I get really into tabletop games such as Dungeons & Dragons and Vampire: the Masquerade. I always play a ranger in the former and Clan Brujah in the latter.

Sunday, September 5, 2021

Lambeosaurus: Beast of the Week

 This week we will be checking out another amazing hadrosaur.  Make way for Lambeosaurus!

Lambeosaurus was a hadrosaur ("duck-billed" dinosaur) that lived in what is now Canada during the late Cretaceous period, 75 million years ago.   Adults measured 23 feet (7 meters) long from beak to tail.  The genus name translates to "Lambe's Lizard" in honor of the paleontologist, Lawrence Lambe.  Like all hadrosaurs, Lambeosaurus would have eaten plants when alive.

Lambeosaurus lambei life reconstruction in watercolors by Christopher DiPiazza.

Lambeosaurus was a member of the lambeosaurine group of hadrosaurs, which are characterized by having more narrow snouts and often elaborate, hollow, bony crests on their heads.  Corythosaurus and Hypacrosaurus are two other members of this group which were particularly closely related to Lambeosaurus.  Within the Lambeosaurus genus there are actually two distinct species, Lambeosaurus lambei and Lambeosaurus magnicristatusLambeosaurus lambei was discovered first, lived earlier by a few million years, and had a crest that jutted out in the front accompanied by a solid, bony, rod-like structure growing out of the back of its head.  Lambeosaurus magnicristatus lived slightly more recently, and had a larger, rounder crest that grew forward out of the top of its skull. 

There are two species of LambeosaurusLambeosaurus lambei (left) and Lambeosaurus magnicristatus (right). 

The exact function of Lambeosaurus' crest may always be a mystery, but many experts agree it most likely evolved for some sort of display within the species.  The front portion of the crest was also hollow, and attached to the nasal cavities of the animal, so it is commonly suggested they had a role to play in making unique sounds, as well.  Among Lambeosaurus lambei specimens, there seems to be a variety in crest size between individual adults.  Some paleontologists believe that this represents sexual dimorphism, the males with slightly larger crests than the females.  Babies and juveniles are also known from Lambeosaurus, which had tiny crests that start in the front of the skull, and expanded backward as the animals matured. 

Skull cast of Lambeosaurus lambei on display at the Academy of Natural Sciences in Philadelphia.

Lambeosaurus had a very long, slender snout that was tipped with a rounded bill.  This feature would have been ideal for clipping tough vegetation that would then be ground up by many small teeth in the back of the mouth, which acted together as a unit, called a dental battery.  Like all reptiles, Lambeosaurus would have been able to regenerate teeth continuously as they became worn or lost.  

Baby Lambeosaurus skull on display at the Royal Tyrrell Museum. (photo credit: Roland Tanglao)

Like all hadrosaurs, Lambeosaurus would have been able to walk on all fours or just its hind legs, as a biped, depending on what suited it.  Its front limbs were relatively the middle three fingers on each hand were fused together and tipped with a large hoof-like claw.  Its tail was long and extremely robust, and would have served as a counterbalance for the animal if it walked or ran on its hind legs.  The tail also could have served as an effective weapon to keep predators away or even knock them over if swung hard enough, if needed.  

References

Dodson, Peter (1975). "Taxonomic implications of relative growth in lambeosaurine dinosaurs". Systematic Zoology24 (1): 37–54.Simpson, D.P. (1979). Cassell's Latin Dictionary (5th ed.). London: Cassell Ltd. p. 883. 

Evans, David C.; Reisz, Robert R. (2007). "Anatomy and relationships of Lambeosaurus magnicristatus, a crested hadrosaurid dinosaur (Ornithischia) from the Dinosaur Park Formation, Alberta". Journal of Vertebrate Paleontology. 27 (2): 373–393.

Horner, John R.; Weishampel, David B.; Forster, Catherine A. (2004). "Hadrosauridae". In Weishampel, David B.; Dodson, Peter; Osmólska, Halszka (eds.). The Dinosauria(2nd ed.). Berkeley: University of California Press. pp. 438–463.

Sunday, August 22, 2021

Mastodonsaurus: Beast of the Week

 This week we'll be checking out a gigantic swamp beast.  Make way for Mastodonsaurus!

Mastodonsaurus was a member of the ancient order of vertebrates, called the temnospondyls, which were related to today's amphibians. (some studies suggest modern amphibians are also a branch of the temnospondyl order) Mastodonsaurus includes a few species, which lived in what is now Eurasia, fossils found in Germany, England, and Russia, during the Triassic period, 230 million years ago.  Mastodonsaurus was a meat-eater when alive and the largest species, Mastodonsaurus giganteus, could exceed 20 feet (6m) in length from snout to tail.  The genus name translates to "breast tooth lizard" which is a bit misleading since it wasn't a lizard nor do any of its teeth particularly resemble breasts of any kind. (But the broken one that was first examined by scientists who named it apparently did.)

Life reconstruction in watercolors of a territorial dispute between two Mastodonsaurus giganteus by Christopher DiPiazza.

Mastodonsaurus had a proportionally huge, flattened, skull, with large eye sockets on the top.  This is an adaptation to be able to raise its eyes above the water and still stay relatively hidden while stalking prey. Modern crocodilians and certain frogs have the same feature for the same purpose.  The inside of Mastodonsaurus' mouth was lined with sharp, cone-shaped teeth, ideal for making sure whatever animal it bit couldn't escape.  The most astonishing feature, however, was the pair of extra long, tusk-like teeth growing up from the tip of its bottom jaw.  These two teeth would fit through actual holes present in the top of the animal's mouth when closed.  The rest of Mastodonsaurus' body reinforced the idea that it was primarily an aquatic animal.  It's legs were proportionally small and weak, but it had a long, strong tail that it could have used to propel itself through the water of its swampy home.  

Mastodonsaurus skull on display at the Muschelkalk Museum. Photo credit: Ghedoghedo 

Mastodonsaurus would have been the top predator of its environment.  At its adult size it would have been able to devour a variety of other animals that it shared its habitat with.  It was likely an ambush predator, relying on stealth to snap up fish that swam to close to its mouth, or even grabbing land animals as they came to the water to drink.  It is unlikely Mastodonsaurus would have left the water much when alive.  Its anatomy just wasn't equipped to spend extended time on land.  There are also fossil beds of many Mastodonsaurus that all died practically on top of each other.  This implies they were trapped in a body of water that was drying up as they were forced closer and closer to the center until their deaths.  

References

Damiani, Ross J. (2001). "A systematic revision and phylogenetic analysis of Triassic mastodonsauroids (Temnospondyli: Stereospondyli)". Zoological Journal of the Linnean Society. 133 (4): 379–482.

Moser, MarkusSchoch, Rainer 2007 "Revision of the type material and nomenclature of Mastodonsaurus giganteus (Jaeger) (Temnospondyli) from the middle Triassic of Germany" Palaeontology 505:1245-1266:

Schoch, R.R. (1999). "Comparative osteology of Mastodonsaurus giganteus (Jaeger, 1828) from the Middle Triassic (Lettenkeuper: Longobardian) of Germany (Baden-Württemberg, Bayern, Thüringen)"Stuttgarter Beiträge zur Naturkunde Serie B278: 1–175.

Sunday, July 25, 2021

Giganotosaurus: Beast of the Week

This week we'll be checking out a giant carnivore that has been continuing to gain popularity since its discovery.  Make way for Giganotosaurus carolinii

Giganotosaurus was a meat-eating dinosaur that lived in what is now Argentina during the late Cretaceous period, between 99 and 97 million years ago. The genus name translates to "Giant Southern Lizard".  Giganotosaurus is famous for being one of the largest carnivorous dinosaurs known, the largest specimens estimated at about 41feet(12.5meters) long from snout to tail, based on known fossil material.  

Gigianotosaurus life reconstruction in watercolors by Christopher DiPiazza

Gignotosaurus was a member of the carcharodontosaurid family, a branch of carnivorous dinosaurs that flourished during most of the Cretaceous period as the dominant land predators until they were eventually replaced by tyrannosaurids in the northern hemisphere and abelisaurids in the southern hemisphere.  Carcharodontosaurids are characterized by having relatively long skulls that slightly taper towards the tip of the snout. Their jaws were lined with blade-like ,serrated teeth, which is how this group earned its name, the "shark-toothed lizards".  Acrocanthosaurus and Concavenator are two other members of this family that have been featured on Prehistoric Beast of the Week.  

Giganotosaurus had a huge skull that measures between five and six feet long. The surface above its snout and eyes was rough in texture, implying there was some sort of horn-like keratin material growing there in life.  This dinosaur probably had some kind of low crest on its head in life either for display within the species, or possibly for some sort of combat.  The teeth were blade-like and serrated, like those of a shark, and the jaws were long and laterally narrow.  The tip of the lower jaw jutted down a bit, forming a "chin".  It is thought that this "chin" could have added extra momentum if Giganotosaurus was making contact with the front of its jaws as it bit.

Giganotosaurus skeletal mount on display at the Fernbank Museum of Natural History in Georgia. (image credit: Johnathan Chen)

All these jaw features imply Giganotosaurus wasn't adapted for crushing bone with its jaws, but rather making fast slices through soft tissue.  This reflects a hunting strategy aimed at making the prey animal bleed to death with deep cuts, rather than paralyzing it with a crushing blow, like a Tyrannosaurus might.  This makes sense since Giganotosaurus would have shared its environment with several large species of sauropod dinosaurs, some of which were larger than Giganotosaurus, and all of them would have been slower, so the strategy of slicing hunks of flesh off over a longer period of time, causing severe bleeding, makes sense for hunting a prey item that was too large to be taken down in one powerful bite.

That is all for this week!  Feel free to comment below!

References

Calvo, J. O.; Coria, R. A. (1998). "New specimen of Giganotosaurus carolinii (Coria & Salgado, 1995), supports it as the largest theropod ever found". Gaia15: 117–122.

Coria, R. A.; Salgado, L. (1995). "A new giant carnivorous dinosaur from the Cretaceous of Patagonia". Nature377 (6546): 224–226.

Coria, R. A.; Currie, P. J. (2002). "The braincase of Giganotosaurus carolinii (Dinosauria: Theropoda) from the Upper Cretaceous of Argentina". Journal of Vertebrate Paleontology22(4): 802–811.

Leanza, H. A; Apesteguía, S.; Novas, F. E; de la Fuente, M. S (2004). "Cretaceous terrestrial beds from the Neuquén Basin (Argentina) and their tetrapod assemblages". Cretaceous Research25 (1): 61–87.

Novas, F. E.; Agnolín, F. L.; Ezcurra, M. D.; Porfiri, J.; Canale, J. I. (2013). "Evolution of the carnivorous dinosaurs during the Cretaceous: The evidence from Patagonia". Cretaceous Research45: 174–215.

Therrien, F.; Henderson, D. M.; Ruff, C. B., 2005, "Bite Me: Biomechanical models of theropod mandibles and implications for feeding". In: Carpenter, K., The Carnivorous Dinosaurs. Life of the Past. Indiana University Press. pp. 179–237

Monday, July 12, 2021

Hypacrosaurus: Beast of the Week

This week we're checking out an important and well-studied plant-eater.  Make way for Hypacrosaurus!

Hypacrosaurus was a hadrosaurid ("duck-billed" dinosaur) that lived in what is now North America during the late Cretaceous period, between 75 and 67 million years ago.  When alive, like all members of its family, it would have eaten plants.  The largest adults measured about 30 feet (9.1 meters) from beak to tail.  The genus name translates to "Near the Highest Lizard" which is a seemingly odd genus name.  It's because the first Hypacrosaurus fossils uncovered were soon after the first Tyrannosaurus (the "highest" of dinosaurs at the time) fossils, and the two were similar in size, T.rex being a bit larger.  (This comparison made more sense at the time when we knew about WAY fewer dinosaurs.)

Hypcrosaurus altispinax life reconstruction in watercolors by Christopher DiPiazza.

Hypacrosaurus was a member of the lambeosaurine group within the hadrosaur family.  Lambeosaurines are known for having hollow bony crests growing from the tops of their skulls.  Parasaurolophus, and Hypacrosaurus' especially close relative, Corythosaurus are more famous members of this group.  Hypacrosaurus' crest was similar to Corythosaurus' in that it shaped almost like a sort of round helmet that starts about midway up the snout and ends at the base of the skull, behind the head.  Hypacrosaurus' crest was a bit shorter and wider than Corythosaurus', however.  Like its relatives, the crest was hollow and could have aided it in making specific kinds of sounds meant to communicate with members of its own species.  The crest also could have very well aided in visual display, since we know these dinosaurs grew the crests as they matured.  Different-sized and shaped crests would indicate the maturity of an individual when viewed by its peers.

Hypacrosaurus altispinax skull on display at the American Museum of Natural History in New York.

Hypacrosaurus, the genus, actually includes two distinct species that lived during different times.  Hypacrosaurus altispinax was discovered first and was found in Alberta, Canada.  Hypacrosaurus stebingeri was slightly smaller and had a lower crest than H.altispinax and was discovered in Montana, USA.

Hypacrosaurus is one of the few kinds of fossil dinosaurs scientists were able to find lots of eggs and babies from.  So much so, that they were able to study how these dinosaurs grew and aged throughout their lives.  Hypacrosaurus babies had only tiny, barely noticeable crests, and grew extremely fast for animals their size.  In fact, according to studies that examined multiple specimens of various sizes and looking at markings on the inside of their limb bones, paleontologists suggest Hypacrosaurus was sexually mature between only two to three years of age.  They didn't reach full adult size, however, until they were about ten to twelve.  The reasoning why an animal would have grown so quickly could have something to do with a need to avoid predation.  As the dinosaur grew, the variety of predators able to hunt it diminished.  The ability to reproduce early in life also probably played a part in its relationship with predators, since most dinosaurs likely never made it to adulthood.  

Skull of a baby Hypacrosaurus on display at the Museum of the Rockies in Montana.

Lastly, scientists were able to find preserved cells in beautifully preserved cartilage of a baby Hypacrosaurus specimen.  Not only that, but they were able to observe that these cells were in the process of dividing when the dinosaur died, and ultimately were able to extract traces of genetic material from it!  Not only was this cool for finding dinosaur genetic material, but it also proved that genetic material can survive MUCH longer than previously thought if the conditions are specific enough.

References

Bailleul, A. M.; Zheng, W.; Horner, J. R.; Hall, B. K.; Holliday, C. M.; Schweitzer, M. H. (2020). "Evidence of proteins, chromosomes and chemical markers of DNA in exceptionally preserved dinosaur cartilage"National Science Review7 (4): 815−822.

Cooper, Lisa N.; Lee, Andrew H.; Taper, Mark L.; Horner, John R. (2008). "Relative growth rates of predator and prey dinosaurs reflect effects of predation"Proceedings of the Royal Society B275 (1651): 2609–2615.

Erickson, G.M.; Zelenitsky, D.K.; Kay, D.I.; Norrell, M.A. (2017). "Dinosaur incubation periods directly determined from growth-line counts in embryonic teeth show reptilian-grade development" (PDF)Proceedings of the National Academy of Sciences114 (3): 540–545.

Horner, John R.; Currie, Phillip J. (1994). "Embryonic and neonatal morphology and ontogeny of a new species of Hypacrosaurus (Ornithischia, Lambeosauridae) from Montana and Alberta". In Carpenter, Kenneth; Hirsch, Karl F.; Horner John R. (eds.). Dinosaur Eggs and Babies. Cambridge: Cambridge University Press. pp. 312–336.

Tuesday, June 29, 2021

Thescelosaurus: Beast of the Week

 This week we will be looking at a little dinosaur that definitely deserves more attention.  Check out Thescelosaurus!

Thescelosaurus was a relatively small plant-eating dinosaur that lived in what is now North America, during the latest part of the Cretaceous period, between 68 and 66 million years ago.  From beak to tail the largest specimens were almost 15 feet (4.5 meters) long.  The genus name translates to "godlike lizard/reptile" in reference to how surprised scientists were at how well preserved and complete the first studied specimen's bones were.  

Watercolor reconstruction of Thescelosaurus neglectus by Christopher DiPiazza.

Thescelosaurus is currently known from three species, Thescelosaurus neglectus, which was the first named and lived in the United States, named after the fact that the specimen was kept in a box for years until it was formerly examined for the first time. Thescelosaurus garbanii was also from the United States but was slightly larger and more robust.  Thescelosaurus assiniboiensis was the smallest of the three species and lived in what is now Western Canada.  When alive, Thescelosaurus would have shared its environment with famous dinosaurs, like Tyrannosaurus, Triceratops, Pachycephalosaurus, Acheroraptor, and Edmontosaurus.

In general Thescelosaurus is characterized by being a pretty robust dinosaur, despite the fact that it wasn't overall a very large.  It would have walked on its hind legs, but some suggest it could have possibly moved or rested on all fours at least some of the time.  Its front limbs were relatively long and strong, and tipped with five fingers on each hand.  It had a flexible neck and a proportionally small skull with a narrow beak in the front of its jaws and teeth lining the sides ideal for shredding plants once inside the mouth. This dinosaur also had teeth at the tip of its snout, where the beak was, which may have helped it strip leaves off of stems and shoots as it ate.

Thescelosaurus skeleton on display at the Canadian Museum of Nature in Ottowa, Ontario, Canada.

Some Thescelosaurus also had overlapping bony plate-like structures on their ribs.  At first some believed these were to aid in breathing but they lack the sort of surface texture that normally would imply there were muscles attached in life.  Thanks to specimens of Thescelosaurus that weren't quite mature when they died, we know these plates may have started as cartilage and would have solidified into bone as the animal aged.  Perhaps they provided extra protection in some sort of intraspecies combat only mature individuals engaged in?  We may never know.

That is all for this week!  As always feel free to comment below!

References

Boyd, Clint A.; Cleland, Timothy P. (2008). "The morphology and histology of thoracic plates on neornithischian dinosaurs"Abstract with Programs - Geological Society of America; Southeast Section, 57th Annual Meeting40 (2): 2.Boyd, Clint A.; Brown, Caleb M.; Scheetz, Rodney D.; Clarke, Julia A. (2009). "Taxonomic revision of the basal neornithischian taxa Thescelosaurus and Bugenasaura". Journal of Vertebrate Paleontology29 (3): 758–770. 

Brown; Caleb M.; Boyd, Clint A.; and Russell, Anthony P. (2011). "A new basal ornithopod dinosaur (Frenchman Formation, Saskatchewan, Canada), and implications for late Maastrichtian ornithischian diversity in North America"Zoological Journal of the Linnean Society163 (4): 1157–1198. 

Brown, Caleb Marshall; Evans, David C.; Ryan, Michael J.; Russell, Anthony P. (2013). "New data on the diversity and abundance of small-bodied ornithopods (Dinosauria, Ornithischia) from the Belly River Group (Campanian) of Alberta". Journal of Vertebrate Paleontology33 (3): 495–520. 

Galton, Peter M. (1995). "The species of the basal hypsilophodontid dinosaur Thescelosaurus Gilmore (Ornithischia: Ornithopoda) from the Late Cretaceous of North America". Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen198 (3): 297–311. 

Galton, Peter M. (1997). "Cranial anatomy of the basal hypsilophodontid dinosaur Thescelosaurus neglectus Gilmore (Ornithischia; Ornithopoda) from the Upper Cretaceous of North America". Revue Paléobiologie, Genève16 (1): 231–258.

Stein, Walter W. “The Paleontology, Geology and Taphonomy of the Tooth Draw Deposit; Hell Creek Formation (Maastrictian), Butte County, South Dakota. .” The Journal of Paleontological Sciences, Apr. 2021, pp. 1–108.

Sunday, June 6, 2021

Tlatolophus: Beast of the Week

 This week let's celebrate a newly described dinosaur.  Check out Tlatolophus galorum

Watercolor life reconstruction of Tlatolophus by Christopher DiPiazza.

Tlatolophus was a hadrosaurid ("duck-billed") dinosaur that lived in what is now Coahuila, Mexico, during the Late Cretaceous, about 73 million years ago.  It was a massive animal, measuring about 39 feet (12 meters) from beak to tail and would have eaten plants when alive.  The genus name translates to "word crest" because this dinosaur's bony head crest resembles the Aztec glyph meant to represent speech. 

Aztec word glyph which coincidentally resembles Tlatolophus' crest, just rotated. Originally from Codex Barbonicus. Image taken from Mexicolore.co.uk.

Like many large dinosaur fossils, Tlatolophus is known from incomplete remains.  That being said, the parts that were unearthed give important information about this dinosaur.  Most amazing is the fact that almost the whole skull was intact, including the elaborate crest.  (It's frustrating when a new hadrosaurid, family of dinosaurs known for having diverse crests, is discovered with no head, leaving us completely in the dark as to what it would have really looked like.)  Tlatolophus' crest was shaped like a sideways teardrop, sweeping back, behind the animals head and flaring out at the end.  The crest was hollow and connected to the animal's nasal cavity, suggesting it may have aided in producing some sort of sound in life.  

Photograph of Tlatolophus' beautifully complete skull, featured in the recent paper cited below.

Like all hadrosaurids, Tlatolophus had a beak in the front of its snout which would have had a keratin sheath growing over it in life.  This beak would have evolved for clipping off mouthfuls of vegetation which would then be shredded by the many tiny, tightly packed, teeth in the back of the mouth.  Tlatolophus also likely would have been able to walk on all fours, or on its hind legs depending on what suited it best.  It is thought that hadrosaurids most comfortably walked on all fours, but would rear up to reach higher plants while feeding, or to run faster as bipeds to escape predators.

Tlatolophus also had a long tail, proportionally longer than what is typically seen in other hadrosaurids, which made up about half the animal's total body length.  It is a total mystery why this specific hadrosaurid evolved such a long tail.  Maybe it had something to do with courtship display?  Maybe it was evolved to hit rival adults for dominance?  Long tails are also effective weapons against predators that may try to attack from behind.  A strong impact from a tail like that would surely knock a similarly-sized tyrannosaurid over, giving Tlatolophus time to escape.  We may never know for sure, however.  

It is interesting to note that paleontologists deducted, based on features of the skull, that Tlatolophus was closely related to another, more famous, hadrosaurid that also sported a striking crest, Parasaurolophus.  What's interesting is that Tlatolophus is even more closely related to Parasaurolophus, which is found in Canada and the United States, more than the hadrosaurid that it coexisted with in Mexico, called Velafrons.  It just goes to show how much different populations of closely related dinosaurs were moving around and settling in different areas over the millions of years they reigned.  

That is all for this week!  As always feel free to comment below!

References

Ramírez-Velasco, Á. A.; Aguilar, F. J.; Hernández-Rivera, R.; Gudiño Maussán, J. L.; Rodriguez, M. L.; Alvarado-Ortega, J. (2021). "Tlatolophus galorum, gen. et sp. nov., a parasaurolophini dinosaur from the upper Campanian of the Cerro del Pueblo Formation, Coahuila, northern Mexico". Cretaceous Research. in press: Article 104884.