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Re: Theropod "migrations"



In a message dated 4/25/99 1:25:49 PM EST, tkeese1@gl.umbc.edu writes:

<< I thought Ceratop[s]idae was node-based, with Ceratop[s]inae
 (=Chasmosaurinae) and Centrosaurinae (=Pachyrhinosaurinae) as stem-based
 clades within, meaning that if it's not a ceratop[s]ine or a
 centrosaurine, it's not a ceratop[s]id. I have it as a non-ceratopsid
 ceratopsomorph, just above _Montanoceratops_.  >>

Umm--who cares? I mean about node-based, stem-based, whatnot. Tomorrow the 
definitions will change yet again; I might change some of them myself--a hoot 
until someone else changes them to something else. There's no Code for 
taxonomic definitions, just for taxonomic names. Redefining taxa has a long 
tradition in dinosaur paleontology.

If Ceratopidae, Ceratopinae, and Centrosaurinae form a node-stem triplet (a 
la Sereno), as you have it, then I'd make Turanoceratops a basal ceratopine. 
Supraorbital horns are apomorphic for Ceratopinae and T. has them. So does 
Zuniceratops, by the way, so it's a basal ceratopine, too (don't know which 
is higher up the tree [they're pretty close]; not enough material). 
Montanoceratops has no supraorbital horns, so it's a good candidate for the 
stem below Ceratopidae (which is also where its other characters place it).

But if Ceratopidae and Protoceratopidae form a node-stem triplet with[in] 
Neoceratopia, then the stem from Neoceratopia to the node Ceratopidae is also 
part of Ceratopidae (but outside the two subfamilies), and then 
Montanoceratops is a basal ceratopid rather than a protoceratopid.