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Comment Re:Nothing surprising here (Score 1) 265

Crocodilians and dinosaurs (and birds) share a common ancestor. They are all considered Archosaurs, along with pterosaurs and a handful of other extinct species that don't fit into neatly of those groups.

To put it another way, Archosaurs can be defined as a Blue Jay, an American Alligator, their most recent common ancestor, and all descendants (living and extinct) of that ancestor. (Any living bird and any living crocodilian will satisfy this definition).

Dinosaurs, using a similar definition, can be defined as a Blue Jay, a Triceratops, their most recent common ancestor, and all descendants (living and extinct) of that ancestor. (Any living bird and any ornithithischian dinosaur -- Triceratops, Iguanodon, Stegosaurus, Pachycephalosaurus, etc. -- will satisfy this definition. However, using common extinct saurischian dinosaurs such as Tyrannosaurus or Velociraptor will not.)

Comment Re:The real extinction (Score 1) 93

I think a better measure here is extinction at the genus level. Genuses are more likely to have fossil records and we can speak of the relative decline of the number of genuses in a proposed extinction event.

Exactly. Mass extinctions are measured by the % loss of genera, not a species count.

(Along those same lines, very few people can name more than one dinosaur species, but they can name several genera.)

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