Examining Cryolophosaurus: Shedding Light on a Little-Known and Important Jurassic Dinosaur

An enigmatic theropod Cryolophosaurus: Reviews and comments on its paleobiology

By: Changyu Yun

Summarized by Ohav Harris, a geology major at the University of South Florida and is currently a junior. He plans to pursue a doctorate degree in paleontology and become a paleo-educator in some capacity, either working in a museum or a university. In his free time, Ohav enjoys collecting Pokémon cards, reading manga, and fishing.

What data were used? The author, Yun, used many previously published peer reviewed papers to review and evaluate the ideas that exist regarding Cryolophosaurus’s evolutionary relationships, or phylogenetics. The only known fossil data for this dinosaur are hip fragments, various vertebrae, rib fragments, femurs, part of its foot, and the holotype (the fossil that the description of the genus/species is based on), which include the skull and neck vertebrae – all of which were found in Antarctica. The sparse remains of Cryolophosaurus make it difficult to make definitive statements of its relationship to other theropods (bipedal dinosaurs that are primarily carnivorous), though researchers are confident that it is a theropod. Yun includes an array of possibilities from various sources that attempt to answer the question of this dinosaur’s phylogeny and examines what fossil data of Cryolophosaurus there are to make comments on its ecology and biology.

Methods: Yun analyzes Cryolophosaurus’ anatomy and geographical placement, makes comparisons to better known dinosaurs, and references scientific papers that discuss this Cryolophosaurus to draw conclusions regarding its possible phylogeny, ecology, and biology. Certain features of this animal, like the shape of its skull, the structure of its feet, and the purpose of its skull crest, are discussed and used to support Yun’s claims of the nature of Cryolophosaurus.

Reconstruction of Cryolophosaurus by Daniel Goitom. The defining crest is boldly colored, so as to attract the attention of a mate. Cryolophosaurus’s primitive, needle-like feathers would have been an excellent source of thermal insulation in the Antarctic climate in which it lived.

Results: While the exact phylogeny of Cryolophosaurus is tricky, and not yet fully understood, there are a few things that can be said about it. The skull of Cryolophosaurus has features of tetanurans, dinosaurs that are more closely related to modern birds, like Allosaurus, and earlier, more primitive therapods like Ceratosaurus. Tetanurans and Ceratosaurus are closely related, but took different evolutionary paths. The tetanurans are made up of two groups, carnosaurs and coelurosaurs, which contain a majority of the most famous therapods like Allosaurus and Tyrannosaurus respectively, and all modern birds (descending from the coelurosaurs). Because Cryolophosaurus’ skull has both features of tetanurans and earlier theropods, it can be inferred that it is a transitional fossil that links the first theropods in the Jurassic and all subsequent therapods and modern birds. It is also likely that, based on its shared features between both theropod groups, Cryolophosaurus is an early tetanuran. This possibility is briefly discussed in the paper. It was also determined that Cryolophosaurus was an apex predator in its Antarctic environment, able to make swift movements and out-speed its prey to capture them. This is based on the animal’s astragalus (the bone in the foot between the shin and tarsals) and calcaneum (the bone just under the astragalus that forms the heel) being fused through ossification, or the growth of new bone material. Because dinosaurs walked on their tiptoes, this would not affect their stability as it would for humans. Additionally, those two bones are located right next to each other in dinosaur feet, which means that Cryolophosaurus only had one “ankle” bone where it would usually have had two. Taphonomic evidence (relating to the processes a body undergoes after death, including fossilization), supports the idea of Cryolophosaurus being an apex predator, as herbivore teeth have been found in its stomach. Sauropods, the long-necked dinosaurs, have also been found in the same formation as Cryolophosaurus, which could suggest they were also potential prey. Interestingly, the Cryolophosaurus holotype was found disarticulated with shed teeth nearby. These teeth are believed to have belonged to another Cryolophosaurus, suggesting that this dinosaur may have had cannibalistic tendencies. The characteristic crest of the dinosaur (Fig. 1) is believed to have been used as a display for attracting mates, with differences in bodily characteristics between males and females.

Why is this study important? Cryolophosaurus is an important dinosaur for theropod evolution because it is likely a transitional fossil connecting the earliest therapods to the tetanurans that came after. Understanding this dinosaur’s place in the phylogeny of theropods is important because it can elucidate various unknowns about their evolution. Cyrolophosaurus’ environment was also unique, being the only therapod yet discovered in Antarctica, which was a colder climate than what other dinosaurs in the Jurassic were living in. This provides a new perspective into dinosaur ecology, particularly through the lens of dinosaurs adapted for colder climates.

The big picture: Dinosaur paleontology is generally regarded by the public as being centered around the most popular Late-Cretaceous genera like Tyrannosaurus, Triceratops, and Velociraptor without much consideration for their ecology or even other dinosaurs from different periods. This study sheds light on one such lesser-known dinosaur, Cryolophosaurus, and states its importance to the phylogeny of theropod dinosaurs as well as its ecological role. Understanding the “niche” and lesser known dinosaurs is extremely important to the understanding of dinosaur paleontology, as those dinosaurs often provide much insight, not only into their evolution and development, but also to the unique nature and attributes of dinosaurs as a whole.

Citation: Yun, Changyu, 2020. An enigmatic theropod Cryolophosaurus: Reviews and comments on its paleobiology. VOLUMINA JURASSICA, 2019, XVII: 103–110

My Experience at the Wyoming Dinosaur Center

Ohav here–

Earlier in the spring, I got an email containing a flyer for an internship that grabbed my attention with a simple question: “Do you like dinosaurs and digging in the dirt?”. As an aspiring paleontologist, I thought, to no surprise, “I love both of those things!”, and I looked into the offer further. A few references and an interview later, I had managed to get a position! That May, I would be going to Thermopolis, Wyoming.

When I started my first day, I was surprised at how dense with information the museum was. I knew that being in a small town, the museum would be much smaller than its contemporaries. Even so, I was not prepared for the amount of stuff in that building! Still in awe of all the beautiful specimens in the main hall, the other interns and I began our orientation. There were a handful of programs and activities available which we would work together to lead, the following of which were the most common.

First, were the Museum Tours: the most basic of the activities, but by no means the least fun. It is exactly as it sounds: a tour of the museum. However, we interns were allowed and encouraged to put our own personal spins on them. This meant making our own scripts, deciding which exhibits to focus more on and which can be breezed through, cherry-picking the coolest fun facts to share with our groups, and even including pop culture references. For example, we would often describe the length of our Supersaurus, Jimbo, by using the metric of Jeff Goldblums. Since Jimbo is 120 feet long and Jeff Goldblum is 6’4’’, we estimated that Jimbo was about 19 Jeff Goldblums long. This went over particularly well with those familiar with his iconic role in Jurassic Park.

Second, were the Bus Tours. The Bus Tours were also simple: drive a van full of people up the mountains of the Morrison Formation to our most significant dig site, Something Interesting (SI), and give them a tour of the place. The tour, in short, was a look through a window to about 150 million years ago, and explored not only the dinosaurs found there, but also the geochemistry and even the seasonality of prehistoric Thermopolis.

Third, were the Shovel Readies, which involved taking group(s) up the mountain to one of our four active sites to dig for a few hours. These would occur either in the morning or the afternoon.

Fourth, and my favorite activity of all, was the Dig For a Day program, or DFD. DFDs were a combination of the previous activities plus an expedition to the Sundance Formation, which underlies the Morrison and yields marine fossils. A DFD day would start with an SI tour, followed by a few hours of digging at one of our sites, then lunch, then prospecting (looking for new fossil sites) at Sundance. Although most guests found dinosaurs more interesting than the marine invertebrates, the promise of being able to keep whatever invertebrate fossils they found sweetened the deal. Finally, after the Sundance, we would conclude the day with a museum tour, which included a sneak peek into our collections and prep lab.

Working with so many wonderful people, who themselves are amazing scientists, was an unforgettable experience. Living with them added to the overall experience too, as we all got to know each other quite well, making the group dynamics all the more interesting. Of course, this is expected from a group of people who love dinosaurs and other prehistoric life spending seven weeks together in the same house. More than anything, though, I loved being able to teach guests about the history of life. Because the museum exhibits were organized with a “tour through time” in mind, it was especially easy and fun to walk guests through the steps life took to get to where we are today. In addition to teaching, I was able to learn a lot. The other interns’ tours alone allowed me to gleam a significant amount of information and insight, since their versions always had things I didn’t know in them. Beyond the tours, I learned much from the museum staff who trained us, learning how to find pathologies and taphonomies in fossils from the head prep lab manager and how to find and map them in the field from the dig site manager. In the lab especially, I came to see some of the most interesting things which made me think more and more about the intricacies of dinosaur morphology and what pathologies that they may have developed.

My biggest take-away from my internship was being able to learn from so many people and being able to pass that knowledge on to others. I was extremely fortunate to work in such an amazing establishment and learn so much, as well as make so many good friends. Going up the mountains of the Morrison, nearly every day for seven weeks, was something I won’t forget. Walking where the dinosaurs walked and digging their remains, and being able to educate all the while, was a small taste of what I hope to do in the future. Now, I must say: if you ever find yourself on a road-trip to Yellowstone or otherwise find yourself in Wyoming, please take the time to stop by the Wyoming Dinosaur Museum in Thermopolis. This hidden gem has much to offer, and the town is charming too!