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Re: Leg Bones of Dinos and Non-dinos



Amado Narvaez wrote:

> a critical factor in determining what a dinosaur is involves examining
> the structure of the hind legs...

  That's the way it was taught in an upper-division vertebrate zoology
class I took in 1993.  Evolution of the ball-and-socket hip joint was
particularly stressed, as facilitating the large sizes which some
dinosaurs attained.

  In that context, a question from one of our examinations is amusing.
There were a whole bunch of toy plastic "dinosaurs" (some weren't),
all lined up.  They included brachiosaur, triceratops, _T._rex_,
pteranodon, plesiosaur, and dimetrodon.  The question was, "Which of
these animals would be most suitable for a Hallowe'en costume, and
why?"  (The test date was late October.)  We were supposed to
demonstrate sound zoological reasoning in our response.

  The answer hinged on knowing the hip, foot, and leg anatomy of the
candidates.  The best choice was _T._rex_, and an acceptable
explanation would have been a statement worthy of 1950s-vintage
schlock science fiction: "They walked like men."  Or at least, more
nearly so than any of the other critters offered.

                                --  Jay Freeman, used astrophysicist