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Re: Sauropod Necks



At 01:04 PM 7/16/00 -0400, Dinogeorge@aol.com wrote:
In a message dated 7/16/00 9:54:18 AM EST, sarima@friesen.net writes:

<< But even if so, the ancestors of sauropods must have been very *similar*
to
 prosauropods, in order to get from a _Herrerasaurus_-like condition to the
 sauropod condition.  That is why I said "prosauropod-ish", not
"prosauropod". >>

It more likely went from sauropod-ish to prosauropod-ish to herrerasaur-ish
and, separately, to ornithischian-ish. Early sauropods retain all five
functioning pedal digits, whereas in prosauropods the fifth digit is reduced,
vestigial, or lost (only a splint metatarsal V remains). It is extremely
unlikely that sauropods re-evolved a complete fifth pedal digit from the
prosauropod or herrerasaur condition. The primitive dinosaur state is five
functional pedal digits, from which the dinosaurs with reduced to missing
pedal digits V must be descended.

I wasn't really at that level of detail. The plesiomorphic condition for dinosaurs appears to be a gracile bipedal carnivore. Sauropods are robust, quadrupedal herbivores. The route from the first condition to the second most likely must pass through a stage of intermediate (gracile/robust) semi-bipedal herbivores or omnivores. It is this stage that I was referring to by the phrase "prosauropod-ish".


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May the peace of God be with you.         sarima@ix.netcom.com