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Re: recapitulation



Thanks Dinogeorge, I wanted to respond with precisely the insight you have given, but was waiting to come up with the name of a small therapod with no tooth serrations, yet you said it better and in fewer words! With gratitude! Ray Stanford

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From: Dinogeorge <Dinogeorge@aol.com>
To: zooamy@zoo.latrobe.edu.au; starsong@prodigy.net
Cc: dinosaur@usc.edu
Date: Thursday, January 22, 1998 12:05 PM
Subject: Re: recapitulation

In a message dated 98-01-22 07:26:55 EST, zooamy@zoo.latrobe.edu.au writes:

<< The juvenile skulls of Velociraptor bear distinctive
teeth, they are unserrated and have a constricted base, whereas those of
adults are typical blade-like serrated theropod teeth. Now if ontogeny was
recapitulating phylogeny we would have to assume that the unserrated tooth
with constricted base was the ancestral condition. By outgroup comparison
we can see that the adult tooth morphology is the ancestral one.  >>

In the BCF phylogeny, this is not necessarily the case. The ancestral tooth
morphology--going all the way back to the common ancestor of Dinosauria--could
well be the unserrated teeth with constricted base that are found in the
smallest theropods and birds, from which would be individually derived the
great variety of large, serrated theropod teeth. There is really no such thing
as a "typical" theropod tooth; the teeth are quite distinctive among the major
theropod groups. Large theropod teeth are usually serrated, but the serration
patterns and shapes are distinctive and >all<  might well be derived
independently of one another from the simple, unserrated ancestral form.