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Re: wow! another application form! :-)



On Thu, 3 Dec 1998, luisrey wrote:

> Dinosaurs are as modified reptiles as mammals are

Mammals are no longer considered "modified reptiles" -- or perhaps it
would be more accurate to say that the ancestors of mammals are no longer
considered reptiles.

Reptilia has been defined as the traditional four extant groups (turtles,
tuataras, squamates [lizards+snakes], and crocodylians) plus all
descendants of their most recent common ancestor. This excludes all
synapsids (mammals and proto-mammals, formerly known as "mammal-like
reptiles). But it does include dinosaurs (including birds).

> Maybe humans can also be described as modified, terrestrial fishes?

That's true in a sense -- "fish" is a paraphyletic term including all
craniates except for tetrapods (which includes ourselves). Several taxa
that were formerly limited to "fish" (Osteichthyes and Sarcopterygii) have
been expanded under phylogenetic taxonomy to include tetrapods. 

> Or amphibians?

Amphibia was redefined as all animals sharing more recent ancestry with
living amphibians (frogs, salamanders, blindworms) than with living
amniotes (reptiles and mammals), so, in that sense, we are not modified
amphibians. We are modified tetrapods.

--T. Mike Keesey                                   <tkeese1@gl.umbc.edu>
THE DINOSAURICON                http://www.gl.umbc.edu/~tkeese1/dinosaur