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Re: Re: Ankylosaurs & Nodosaurs



>Again, this depends a lot on the definition of your nodosaurids.  If 
>_Polacanthus_ and its relatives are removed from the nodosaurids (as 
>the polacanthids) then it cuts down nodosaurid diversity by quite a 
>lot.
>But, there is also a view that _Edmontonia_, _Panoplosaurus_, and 
>other Campano-Maastrichtian nodosaurids which can be defined (among 
>other features) by an edentulous premaxilla should be separated as a 
>new family, the Edmontoniidae.  That would mean that the nodosaurids 
>became completely extinct before the end of the Cretaceous.

I believe "Panoplosauridae" would have priority.

>Also, whereas ankylosaurids are known from late in the Cretaceous in 
>North America (_Ankylosaurus_, _Euoplocephalus_, _Dyoplosaurus_), 
>there are no nodosaurids/polacanthids/edmontoniids from the 
>Cretaceous of Asia (at least none that I know of).  I think it's fair 
>to say that in the Late Cretaceous, ankylosaurids had the upper hand 
>over their less heavily-armoured cousins.

Only if you qualify by saying "in ASIAMERICA in the Late Cretaceous".
Asiamerican faunas are very different from European or Gondwana dinosaurian
assemblages in the Late K.

Of course, the Antarctic and European Late K ankylosaurs are nodosaurids or
polacanthids.  South America and Africa have not (yet) yielded Late K
ankylosaurs (that I've heard of), and the Lametans thyreophoran situation is
confused, to say the least.

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