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Timothy Williams wrote:
Gather 20 species of birds at random, pluck off their feathers, and *then*
see how different they look.
Or, let's go one step further. Let's just compare their skeletons. With
most extinct theropods, all we have are dry bones. With modern birds,
distinctions can be made using so much more criteria - plumage, behavior,
internal anatomy, eggs and reproduction, etc. Strip birds down to their
bare bones, and there's not a huge difference between an emu and an
ostrich, or a crow and a starling. If all we knew of these species were
their skeletons, we might put them in the same family.
For these reasons, the "families" of extinct theropod dinosaurs and
"families" of modern birds are not directly comparable, I don't believe.
Chalk and cheese.
Which brings up a very good point: Are the taxonomic "splitters" actually
right? Are there indeed half a dozen species each of Apatosaurus and
Edmontosaurus? Where does individual variation end and specific variation
begin (e.g., Tyrannosaurus rex and Tyrannosaurus "x")? This seems to be a
big part of current paleontological research, and one that I am very
Based on the known material, we are very likely *underdescribing* dinosaur
species. But at the same time we also need to recognize that many things can
never be determined from the fossil record--reproductive habits, colors and
the like. Would it be more accurate, then, to say that dinosaur (or any
fossil vertebrate) species are not species in the traditional sense?
I believe that a better understanding of paleobiogeography may play a key
role in unraveling this riddle. It would be nice to examine regional
variation in wide-ranging genera, such as Triceratops. If there are multiple
species in this genus, they *theoretically* would not be sympatric. An
analogy would be lions and tigers--very similar skeletally, but living in
very different habitats.
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