Cretoxyrhina Denticulata? And A Possible Dwardius?

[Tony Eaton]

Perhaps this Texas artificial dental series of Cretoxyrhina is "primitive" enough to qualify as denticulata versus mantelli? Note the relatively more narrow and straighter crowns, vertical crown striations, and more robust cusplets. These are from the Woodbine/Eagle ford contact area, several feet above the brackish water Ostrea sandstone concretions that help clearly denote the upper Woodbine... The age should be Middle or Upper Cenomanian.

I'm also including a tooth that I pulled from this series. It seems to match "Dwardius" comparing some online pics, or maybe I'm offbase here? There is a funny face in the lengual pic, not sure if you'll notice.

Edited August 13, 2011 by Tony Eaton

[Tony Eaton]

Hieronymus helped point out a tooth that doesn't match too well (out of the 200+ Cretoxyrhina teeth I had found this tooth position perhaps varied the most). Posting a revised dentition replacing the upper 8th tooth counting from the right.

I'm also attaching some clearer picks of the odd ball tooth that may not be a Cretoxyrhina and may perhaps fit in with Dwardius ("Cretolamna") woodwardi???

...............

edit 8/16 with comments on the "Dwardius" like tooth.

I am editing versus posting a reply as to avoid (bumping) a post that isn't garnering any responses

One day I'm sure another person will try to track down if they have a NA Dwardius so here are some references I've come across.

In trying to ID this tooth I've read most of the literature on Cretolamna woodwardi / Dwardius woodwardi. Regarding NA, it seems like most of the discussion is around the lack of specimens. The closest published NA shark that I've found is from figure 6 from the Williamson article cited below. However, the early Turonian example from Arizona has a more rounded "U" shaped root and the root is not as heavily ridged.

Selachians from the Greenhorn Cyclothem ("Middle" Cretaceous: Cenomanian-Turonian), Black

Mesa, Arizona, and the Paleogeographic Distribution of Late Cretaceous Selachians

Author(s): Thomas E. Williamson, James I. Kirkland, Spencer G. Lucas

Source: Journal of Paleontology, Vol. 67, No. 3 (May, 1993), pp. 447-474

Here are some early, associated British specimens for a freely downloadable Geologists' association of the London vol. 13 from 1894 (page 228). Although it is a shame the scanner decided to grab most of the teeth in black and white instead of grey scale it is still clear that the root lobe is more U shaped compared to my tooth. (Browsing google go to page 200 and see lamna appendiculata illustrated.)

http://books.google.com/books?id=EiwRAAAAIAAJ&dq=proceedings%20geologists%20association%201894&pg=PA200-IA3#v=onepage&q&f=false

Ultimately I will conclude that one vague tooth isn't enough to determine what this is. The ridged v like root is more like a primitive Cretoxyrhina than Dwardius, so unless I come across some more teeth to analyze I think this one will have to stay in the unknown category and it may simply be a more primitive Cretoxyrhina?

Edited August 16, 2011 by Tony Eaton

[MikaelS]

Its a C. mantelli or C. agassizensis, depending on how far one wants split up the Cretoxyrhina lineage into chrono-species. Its not the typical Cretoxyrhina lateral but it is nonetheless within the range of variation for that genus.

[Tony Eaton]

Thanks Dr. Siversson.

[irenochka62]

On 09.08.2011 at 09:10, Tony Eaton said:

Возможно, эта техасская серия искусственных зубов Cretoxyrhina достаточно «примитивна», чтобы квалифицироваться как denticulata по сравнению с mantelli? Обратите внимание на относительно более узкие и прямые коронки, вертикальные бороздки и более прочные выступы. Они взяты из зоны соприкосновения брода Вудбайн / Игл, в нескольких футах над солоноватой водой Конкреции песчаника Остреи, которые помогают четко обозначить верхнюю часть Вудбайна ... Возраст должен быть средним или верхним сеноманом.

Я также включаю зуб, который я вырвал из этой серии. Кажется, это похоже на "Двордиуса", сравнивающего некоторые онлайн-фото, или, может быть, я здесь за пределами базы? На лингвистической картинке смешное лицо, не уверен, заметите ли вы.

Did you do this reconstruction of the Cretoxyrhina denticulata dentition yourself?