Discovering Dino Diveristy

Posted on April 9, 2017

What do you think of when you hear “tyrannosaur”? I bet you thought of T-Rex. But did you know that there are over twenty-five species of tyrannosaur species, big and small, spanning millions of years? Before I visited the exhibition Tyrannosaurs: Meet The Family, I didn’t know that either. The interactive exhibit, currently at the Waterloo Region Museum, provides a fascinating family portrait of these fleet-footed carnivores

What is a “tyrannosaur”?

Tyrannosaurs are a group of dinosaurs that ate meat and walked on two legs. They had S-shaped necks, long tails, reduced forelimbs, and long hind legs; they looked like variations of a T-Rex. Tyrannosaur fossils occur in North America and Asia, first appearing near the end of the Jurassic period (152 million years ago). The tyrannosaurs that lived in the Jurrasic were small and hardly apex predators. It wasn’t until the Cretaceous Period (145 – 65.5 million years ago) that the tyrannosaurs got bigger and bigger.

Many tyrannosaur species were discovered after 2000; that’s ~100 years after the first identification of Tyrannosaurus and Albertosaurus. The information in Tyrannosaurs: Meet The Family is excitingly recent including a 2016-discovered species.

Image of Dilong paradoxus and T-rex fossils from the Tyrannosaurs: Meet The Family exhibition.

From mini to massive the tyrannosaurs were a diverse bunch. (Left: Dilong paradoxus; Right: Tyrannosaurus Rex)

Organizing Life

Each species in the exhibition had digitally interactive signage. The signs listed the obvious specs (species names and characteristics) and also included the dinosaur’s “likes” and “dislikes.” It was a cute touch that struck a balance between humor and scientific content. For example, Lythronax argenstes is one of the oldest tyrannosaur species and along with the standard information it:

Likes: Being the oldest member of my family.

Dislikes: Still feeling like T-Rex’s younger sibling!

In case you were wondering, L. argestes is smaller than a T-Rex.

The exhibition presented tyrannosaur fossils and skeletons as separate species, but what is a species? How do you distinguish one species from another? Biologists define species in many ways, and each framework is called a “species concept.” The most well-known is the “Biological Species Concept” described by Ernest Mayer:

A species is a reproductive community of populations (reproductively isolated from others), which occupies a specific niche in nature.

-Ernest Mayer (1982)

“Reproductive isolation” means that interbreeding cannot happen either because the offspring will not survive or offspring can survive but are sterile. A mule is a good example; it’s a cross between a male donkey and a female horse. Mules can be born and survive to adulthood, but they are usually infertile. Under the Biological Species Concept, horses and donkeys are different species because they do not produce fertile young.

The Biological Species Concept is useful but its universality is debated. Dinosaurs are extinct. We have no idea about their reproductive habits. The Biological Species Concept is not applicable here, and other species concepts come into play. The one that’s relevant to Tyrannosaurs: Meet The Family is the “Morphological Species Concept.” Morphology is what a living thing looks like, i.e. its form and its structures. When a paleontologist finds a fossil skeleton, they examine the morphology and compare it to a known species and determine whether or not the fossils share common structures.

The Morphological Species Concept is not without limitations. Morphology can vary between individuals and can change throughout an organism’s life. Not only can we humans look different from one another, but humans change in size and proportions as we grow from infants to adults. The same goes for other animals. The controversial dinosaur Nanotyranus lancensis has a thin, slender skull among other unique features and is argued to be either a juvenile T-Rex or a completely separate species.

Regardless, morphology is one of the best tools at a paleontologist’s disposal and can be one of the most salient ways for non-scientists to identify species differences. The exhibition’s digital signage highlighted key structural differences between the tyrannosaur species on display. One wall presented the skulls of several tyrannosaurs and pointed out the specific differences in head width and shape, the presence of “horns” or crests, and the variations in teeth. Tooth shape is not only an important morphological trait, but it also gives scientists ecological information. Different teeth do different things, and paleontologists can get a sense of a tyrannosaur’s diet by examining the shape and orientation of the teeth.

Tyrannosaur teeth varied from thin and knife-like for shearing meat (left) or stocky and robust for crushing bones (center).

Tyrant lizards

Tyrannosaurs are one of the best-described dinosaur groups due to a wealth of fossil information and constant research on the various species. However, there are still controversies about how the tyrannosaurs grew and aged (like with Nanotyrannus) and how they evolved. Up until last year, there was a ~20 million year gap in the tyrannosaur fossil record. Paleontologists finally got answers to important questions about how tyrannosaurs evolved to such enormous sizes in 2016 after scientists discovered a horse-sized tyrannosaur in Uzbekistan. Before then, they didn’t have this “missing link” in tyrannosaur sizes.

The transition from small to titanic is an important one and gave rise to the giant apex predators of the late Cretaceous (80-66 million years ago) including T-Rex. Ironically, Tyrannosaurus rex, which we all know and love, was one of the last members of the tyrannosaur group. Its fossil record spans the end of the Cretaceous, right at the cusp of the great extinction that wiped out the dinosaurs.

Tyrannosaurs: Meet The Family features physical, digital and immersive interactives for all ages.

Tyrannosaurs: Meet the Family contains cutting-edge science plus the added fun of immersive interactives with CGI dinosaurs of all sizes. The exhibition is accessible to young visitors but comprehensive enough to provide a wealth of information for adults. It covers the who, where and when of tyrannosaurs and gives visitors a big picture of this iconic dinosaur group through evolutionary time.

The exhibition was developed in Australia, and this is its first time in North America. It runs until April 30th at the Waterloo Region Museum. If you’re in the Kitchener-Waterloo region before then, I suggest you visit it before it’s gone.

Stay Curious,