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Ankylosaurs (was Re: Birds and mosasaurs)



At 10:54 AM 2/13/98 -0700, LN Jeff wrote:
>>  I agree that Bathonian 
>> teeth are still regarded as possibly dromeosaur or troodont or, with at
least equal 
>> probability, something entirely new.  
>
>     It would make them a prety long-lived lineage, I admit.  Howver,
>ankylosaurs extend from at least the late Jurassic (and further?) until
>the latest Cretaceous.  I do not know if the Cretaceous ankylosaur
>FAMILIES extend back to the Jurassic (someone who knows more might say
>something),

The Middle Jurassic ankylosaur Sarcolestes is included by most workers in
Nodosauridae (a family which makes it to the latest Cretaceous), and the
Middle Jurassic Tianchisaurus in Ankylosauridae (ditto).  Late Jurassic
representatives would be Dracopelta and Mymoorapelta, respectively.

Incidentally, tucked away in the Currie & Padian and Farlow & Brett-Surman
volumes are interesting new aspects of ankylosaur systematics, forthcoming
from Carpenter, Kirkland, Vickaryous, Ryan, and others.

Ankylosauria is defined as all taxa closer to Ankylosaurus than to
Stegosaurus (Carpenter's Ankylosauria chapter in C&P), with Nodosauridae and
Ankylosauridae apparently stem-defined sister taxa of each other
(presumably, everything closer to Nodosaurus than to Ankylosaurus, and vice
versa).

Ankylosauridae is further divided into Polacanthinae and the unnamed group
containing Shamosaurinae and Ankylosaurinae. (Vickaryous & Ryans chapter on
Ornamentation in C&P).  Shamosaurine ornamentation is characterized by
indistinct cranial scutes, whereas those of ankylosaurines are discernible
rostrally.

Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:th81@umail.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661