Re: New *Anchisaurus* paper

["Tim Williams" <twilliams_alpha@hotmail.com>]

> Yates, A.M., 2004.  *Anchisaurus polyzelus* (Hitchcock): The Smallest Known 
> Sauropod Dinosaur and the Evolution of Gigantism among Sauropodomorph 
> Dinosaurs.  Postilla 230: 58 pp.

I just read this over the weekend.  Nice work by Adam.

A few tidbits that stuck in my memory:

The phylogenetic position of _Herrerasaurus_ flip-flops between inside and 
outside the Theropoda, and Yates (2004) suggests that the theropod-like 
characters of _H._ (e.g., intramandibular hinge; elongate grasping/raking 
manus) may be due to convergence, and associated with a hypercarnivorous 
ecology for _H._.

_Mussaurus_ (which has procumbent teeth in the upper and lower jaws) shows 
many non-prosauropod-like characters, and so is unlikely to be a 
prosauropod.

_Ammosaurus_ is sunk into _Anchisaurus_, and the differences previously used 
to separate the two genera are attributed to size/ontogeny (e.g., 
"broad-footed" _Ammo_ vs "narrow-footed' _Anchi_) and postmortem damage to 
the material.

At least two sauropodomorph taxa are known from the Early Jurassic of New 
England: the basal sauropod _Anchisaurus polyzelus_ (including _Ammosaurus 
major_, _Yaleosaurus colurus_) and another taxon (previously referred to 
_colurus_) that differs from _Anchisaurus_ in the morphology of the manus.  
This second taxon shows affinities to the Plateosauria, and is therefore a 
true prosauropod (sensu Yates).

The _Ammosaurus_ material from the Navajo Sandstone of Arizona does not 
belong to _Anchisaurus_, but to a prosauropod that is possibly related to 
_Massospondylus_.  (Interesting, massospondylid material has been previously 
described from Arizona, but from the Kayenta Formation)


Tim

_________________________________________________________________
FREE pop-up blocking with the new MSN Toolbar ? get it now! 
http://toolbar.msn.com/go/onm00200415ave/direct/01/