BSCI392
11-30-07
Flying Theropods

Adapted from notes for GEOL104 by Tom Holtz

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Coelurosauria (Middle Jurassic - Recent) includes a bewildering diversity of forms, each with ecological specializations of interest. Taken as a whole, their evolution reflects a trend toward increasing "birdiness." Some specific trends include:

Coelurosaur diversity: We discussed tyrannosaurs and ornithomimosaurs in the previous lecture. A couple of other landmarks in the evolution of coelurosaur trends include:

Oviraptorosauria ("oviraptors"). (Early - Latest Cretaceous) North America and East Asia: Distinctive, with boxy skulls and a tendency to lose teeth develop impressive crests. They share with more birdlike theropods:

Despite this proto-birdiness, some oviraptors lived distinctly non-birdy lives. Indeed, the largest oviraptorosaur, Gigantoraptor was the size of a medium-sized tyrannosaur.

Alvarazsauridae. (Late Cretaceous): E.G.: Shuvuuia -slender chicken - turkey sized runners with:

Eumanirpatora: (Middle Jurassic - Recent) The coelurosaur flight-plan

Archaeopteryx - "The first 'bird'" (Late Jurassic)

When first discovered, in the 1860s, this creature was the only known feathered fossil. Thus, for over a century it has been a fundamental benchmark in paleontology - "the first bird." As more specimens of Archaeopteryx have been found and studied, and as OTHER feathered theropods have come to light over the last ten years, Archaeopteryx has come to seem less and less birdy. Indeed, if we were to see a living one, it would seem immediately weird with its:

To us, it represents something like the basal condition of Eumaniraptora, the monophyletic group of coelurosaurs in which feathers became functionally coupled with aerodynamics. Among their derived features:

Basal members of the major eumaniraptoran groups were broadly similar: