Phys. Sci 20 – Intro Marine Environment
Rise of the Tyrannosaurs – Scientific American, May 2015, p. 34-41.
When most people think of Tyranosaurs, they usually think only of Tyranosaurus rex,
the gigantic apex predator which lived from approximately 73 to 66 million years ago
during the late Cretaceous age, the final few million years of the age of dinosaurs. The
article, however, describes the long evolutionary history of the Tyranosaurs, going back
at least 170 million years to the mid-Jurassic age.
The great, powerful Tyranosaur lineage started out their evolutionary journey as small,
bipedal, human-sized predators, and for the most part were characterized by relatively
small dinosaurs. Recently discovered, beautifully fossilized Tyranosaur specimens from
China show that many of these dinosaurs were covered with course feathers. The
feathers, which may have been used for insulation, display, or both, further highlight the
evolutionary relationship of small predatory dinosaurs and birds. Also, an insulating
purpose of the feathers imply that the animals were at least partially warm blooded.
While no direct evidence is as yet available, it is likely that even the 10 to 12-ton
Tyranosaurus rex, and related large species, were partially covered in down or feathers
during some stage of their lives.
All Tyranosaurs became extinct at the end of the Cretaceous age, 66 million years ago.
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