Chris,
Are you suggesting that there was not an enormous catastrophe at K-T?
Was there a virus that selectively wiped out dinosaurs, ammonites and
enantiornithines, but crocs were immune to it (he asks half-seriously)?
At least I'm glad you admit that Goniopholididae may have been among
the extinctions at K-T. What about Peirosauridae and Paralligatoridae? Or
are those families cladistically unacceptable taxa?
Furthermore, I find it hard to believe that every species of dyrosaurid
and sebecosuchian, plus all species of the crown group at K-T, all made it
through with no losses. Were they all so endowed with coping mechanisms
that it far surpassed those of all of the dinosaurs and the vast majority of
birds.
I don't think the fossil record is good enough to come to such a
conclusion. Anyway, I would be interested to know about how many
crocodyliform genera you think successfully crossed K-T. Certainly more
than 5, but is it more than 20? I think that was the gist of the original
question (to which I answered that it was an absolute minimum of five).
--------Ken
******************************************
From: chris brochu <christopher-brochu@uiowa.edu> Reply-To: christopher-brochu@uiowa.edu To: dinosaur@usc.edu Subject: Re: K-T crocodylians Date: Tue, 24 Jul 2001 19:30:03 -0400
> I personally can't imagine how they could get through >unscathed.
I see two problems with this statement:
1. It presupposes that there really was an enormous catastrophe at the end of the Cretaceous. It's not my crocodylocentric view coloring my perspective here - remember, I've worked on dinosaurs too.
2. There really, honestly, truly are no data to indicate anything other than normal background extinction rates within crocodyliforms, and none at all within crown-group Crocodylia. The only lineage I see biting it within the Maastricthtian (not necessarily at its end) is "Goniopholididae" (probably not monophyletic and hence not natural), and it's not a crocodylian assemblage. There simply is nothing to suggest any kind of elevated extinction rates within the group. Whether you, or anyone else, cannot imagine such a scenario is at variance with what we actually see.
chris
------------------------ Christopher A. Brochu Assistant Professor Department of Geoscience University of Iowa Iowa City, IA 52242
christopher-brochu@uiowa.edu 319-353-1808 phone 319-335-1821 fax
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