The Common Descent Podcast

Listen to Episode 120 on PodBean, YouTube, Spotify, or your favorite alternative!

The most famous dinosaur of all time didn’t come out of nowhere. T. rex has a long history of cousins and ancestors, whose evolution and lifestyles have been the subject of mountains of research, debate, and popular depictions. This episode, we discuss the whole family tree of Tyrannosaurs.

In the news
Venom might have helped drive the diversity of fish and insects
One tusk reveals a mammoth’s life travels
Jurassic croc cousin is first of its kind in South America
The Sixth IPCC Report is out; climate change is scary, but there’s hope

The Tyrants

Tyrannosaurus rex was first named and described in 1905, the largest and most complete carnivorous dinosaur known at the time, and it soon earned super-stardom among paleontologists and the public. For a long time, T. rex represented nearly everything we knew about its lineage, the tyrannosaurs. But in the 21st century, a bevy of new discoveries and innovative research has revealed more details of this group: their early members, their diversity, and trends in their evolution.

The earliest tyrannosaurs didn’t look much like T. rex. Many were relatively small (3-5 meters long), with slender skulls and long arms, and some, like Proceratosaurus and Guanlong, had flashy head crests. The oldest known tyrannosaurs are from the Middle to Late Jurassic, and at that time they had already spread to Asia, Europe, and North America. Throughout the Cretaceous, tyrannosaurs further diversify across these northern continents, and in the Late Cretaceous, we see the emergence of a more familiar group called Tyrannosauridae.

The members of Tyrannosauridae include T. rex and many of its cousins: Albertosaurus, Tarbosaurus, Alioramus, and more. These dinosaurs have heavily built skulls with thick teeth and reinforced bones that supported a powerful bite. They also have long, slender legs well-adapted for efficient running and walking. And many of them were quite large, often reaching 10 meters (35 feet) long and weighing over a ton, while the largest species, including T. rex itself, could be over 12 meters (40 feet) and weigh several tons. These were dominant predators, superbly adapted for chasing prey and crushing bones.

Tyrannosaur lifestyles

Lots of research has been dedicated to the details of tyrannosaur diets. Evidence from coprolites and bite-marked bones suggests these predators were in the habit of shattering bone, which might have provided them with extra mineral nutrients. Research on T. rex suggests that tyrannosaurs had excellent senses of smell (with large olfactory lobes in their brains) and vision (with large, forward-facing eyes), and their limb and body proportions made them not only agile, but also quick and energy-efficient in motion.

Tyrannosaurs would have been striking to look at. They likely all had some degree of feathers (Yutyrannus and Dilong from China have been found with preserved feathers, and all tyrannosaurs are descended from ancestral feathery coelurosaurs), many had ornamented heads (proceratosaurids had crests and tyrannosaurids had skulls covered in bumps and knobs, with two small bosses over the eyes), and occasional skin impressions provide evidence of scales of varying shapes and sizes.

In recent years, a lot of research has been devoted to tyrannosaur ontogeny – growth and development. Though there is only scant evidence of tyrannosaur embryos, some species, like Tyrannosaurus, Tarbosaurus, and Albertosaurus, are known from many specimens of various ages, giving us a great look at how these animals changed as they grew. When it came to the largest species, teenage tyrannosaurs were so different from adults that they’re thought to have lived very different lifestyles, occupying different ecological niches as they grew.

Learn More

If you want an accessible overview of all things tyrannosaur, we recommend Dr. David Hone’s book The Tyrannosaur Chronicles: the Biology of the Tyrant Dinosaurs

If you prefer videos, here are some recent virtual talks about tyrannosaur biology:
Dr. Thomas Holtz, 2021
Dr. David Hone, 2017
Dr. Stephen Brusatte, 2015

T. rex growth series studied in incredible detail, 2020 (semi-technical)
Brusatte and Carr 2016. The phylogeny and evolution of tyrannosauroid dinosaurs (technical)

Stevens 2004. Binocular vision in theropod dinosaurs (Technical, paywalled) This includes the information on T. rex vision that we discussed in the episode

Some recent tyrannosaur finds we mentioned in the episode:
Moros, 2019
Dynamoterror, 2018
Nanuqsaurus, 2014

—

If you enjoyed this topic and want more like it, check out these related episodes:

• Episode 21 – Dinosaurs, an Introduction
• Episode 42 – Spinosaurs
• Episode 87 – Ceratopsians (Horned Dinosaurs)
• Episode 101 – Sauropods
• Episode 69 – Ankylosaurs

We also invite you to follow us on Twitter, Facebook, or Instagram, buy merch at our Zazzle store, join our Discord server, or consider supporting us with a one-time PayPal donation or on Patreon to get bonus recordings and other goodies!

Please feel free to contact us with comments, questions, or topic suggestions, and to rate and review us on iTunes