Changing Our View of Dinosaurs: The Deep Roots of Bird Evolution

For many of us, the movie, Jurassic Park, summarizes our concepts of dinosaurs: giant long-toothed ferocious reptiles. Though the Victorians once considered them slow, stupid, and plodding, for those who grew up in the Jurassic Park era, dinosaurs were smarter, more vicious, and fast as hell.

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While these features may well have been true of these animals, our reptilian concepts may be decidedly Victorian and out-of-date. Though I had heard about dinosaurian plumage, it wasn’t until recently after reading My Beloved Brontosaurus by Brian Switek that I realize the likelihood that most, if not all, dinosaurs had some sort of plumage. For instance, Godefroit et al. (2014) recently reported a finding of an early ornithiscian dinosaur named Kulindadromeus zabaikalicus dating from the Jurassic of Siberia. Fossils of this animal showed evidence of a mix of both scales and feathers, which strongly suggests that much of the dinosaur clade may have shared these features given that the animal was an earlier non-therapod ancestor to the monstrous giants with which we’re more familiar.

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Illustration of K. zabaikalicus from Godefroit et al. (2014).

Though there may still be some ongoing debate about the nature of these feathery fossil imprints (some scientists have proposed they’re actually collagen imprints, not protofeathers), the prevailing scientific opinion seems to be in support of plumage. For instance, amber-encased feathers from the Late Cretaceous found in Grassy Lake, Alberta, Canada, show a range of finely detailed feather morphologies, ranging from avian-like feathers down to simpler protofeathers seen in dinosaur fossil imprints, strongly supporting the notion that non-avian dinosaurs likely had feathery appendages.

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A fossilized protofeather from McKellar et al. (2011).

Artist renderings of dinosaurs are starting to dramatically change to reflect all this knowledge. In fact, in this month’s Scientific American, there’s an article by paleontologist, Stephen Brusatte, called “Rise of the Tyrannosaurs” with illustrations that dramatically reflect changing ideas. It’s that article in particular that prompted me to write the blog today because of how bird-like our ideas of Tyrannosaur are becoming. One Tyrannosaur in particular by the name of Yutyrannus is especially avian in rendering, driving home the fact that dinosaurs had many reptilian features because they were derived from reptiles, but they likely also had many bird-like characteristics which the Victorians could have never even dreamt about just looking at fossilized skeletons. Truly, these animals were a transition between reptiles and birds, and it didn’t take as long as the avian dinosaur, Archeopteryx, for that to be realized.

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From Scientific American.

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