[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Teeth

>  The whole taxonomic story of this thing is a bit confusing so before I say
>  any more, I want to recheck my refs before I get blasted by somebody ;-)
>  It was the other way round: _Creosaurus potens_ was its original name
>  1911) and Gilmore referred it to _Dryptosaurus_ in 1920. It probably
>  in neither genus, and it's presently a nomen dubium.

Thanks George. You (partially)saved me the trouble. Bear with me, I am on
night shift and it may take me some time to follow through but I will get to
it! ;-)
 Rereading your original question, 

>>Any chance that _Dryptosaurus potens_ is based on your acro?<<

The answer would be a yes and a no. If you have Lull 1911 handy, refer to
figures 1 and 2. (p. 513) listed as _A. medius_. This is identical to teeth I
now have. However, I also rechekcked Weishampel, et al's "Dinosauria"
(p,310-311) . Clearly, Lull was referring to two different genera,
 _"Creosaurus potens" _ later to become_ " D .potens" _by Gilmore the other,
_ A. medius_ (Marsh)  and figured by Lull (1911) _as A. medius_ was  later
renamed _D. medius._
Therefore, yes the teeth I refer to as "Arocanthosaur" are the ones that
started off as _A. medius_ then _D. medius_ and as you have said, probably
referrable to neither Allosaurus, Creosaurus or Dryptosaurus.

It was this exact taxonomic problem that started me searching for the true
owner of these large teeth (in the literature as well as in the field). I
found the first one in 1993 and several more subsequently. The whole Allosaur
problem came about because Marsh originally believed that the entire Potomac
series, not just the Arundel Clay was of Late Jurassic age. Upon finding the
specimen in question he immediately attributed it to the other large late
Jurassic carnivore  that of course was Allosaurus. We now know unequivocally
that the Potomac is Early Cretaceous and are reasonably certain that the
Arundel is Aptian in age so Allosaurus _anything_ was out of the question.
Subsequent renamings have only confused the true affinities of the material.

However, using Marsh's original premise that the tooth is "allosaurid"  I
began researching into what allosaurids were still extant by the Aptian in
North America since the genus _Allosaurs_ was long gone by this time. I found
out about Acrocanthosaurus and noticing numerous possible similarities in
both age, stratigrapgy and biota of the  Antlers and Trinity, Cloverly and
Cedar mountain Formations,  I hypothesized that the Maryland material
_should_ be or at least could be related to _Acrocanrthosaurus. atokensis_ .
(And this has become for me a major paleobiogeogrphic study of the early
Cretaceous of North America, with special emphasis on the Maryland fauna).

After seeing the skull of Fran for myself, comparing casts of the teeth and
with a cast from OMNH I feel very confident in referring some of the large
carnosaur teeth to Acrocanthosaurus sp. 

Forthcoming papers by some members of thislist  who are working on Acro
material  may help to ice it for me once and for all!

Thomas R. Lipka
Paleontological/Geological Studies