Cardabiodon Or Cretoxyrhina

[Ramo]

This was found in the upper Greenhorn Limestone of Central Kansas. It seems that there has been quite a bit of confusion between Cretoxyrhina and Cardabiodon over the years. Thought I'd post some pictures so the "shark tooth people" on here could give their opinions.

Ramo

The last photo is the "in-situ" photo when found.

[fossilselachian]

Although I do not have access to any of my reference material at this time, I would call it Cardabiodon.

[missingdigits]

The world expert on Cardabiodon does lurk around here and has been known to offer his expertise every now and then. That would be nice.

Edited May 18, 2014 by missingdigits

[vertman]

Hey, Ramo, Shawn Hamm may be able to tell you for sure. I can send you his email if you want?

[siteseer]

Ramo,

I also think this is a Cardabiodon - rare find and it's in great shape on top of it. It's usually a good idea to just agree with Fossilselachian but I will also back up the ID with some comments since I have a few relevant articles at hand.

When I have an oddball tooth, the first thing I usually do is try to get some idea of the jaw position. Fortunately, both Cretoxyrhina and Cardabiodon are known by at least partial dentitions with Cretoxyrhina more common and known by at least one rather complete dentition.

Your tooth has a curving crown that is also rather high. Right off the bat, I lean away from Cretox because its teeth tend to angle more than curve and your tooth curves enough to make me think it is an upper lateral tooth. Cretoxyrhina upper laterals have a rather low and less tapering crown than Cardabiodon.

Your tooth also has rather prominent lateral cusplets. I haven't seen a lot of Greenhorn Fm. teeth but I know that both Cretoxyrhina and Cardabiodon are in the process of losing their cusplets by this time, the upper Greenhorn being about Middle Turonian age. Cardabiodon seems to bear more prominent cusplets than Cretoxyrhina of this age (especially in the laterals) so that's another indicator of the former.

Your tooth is one of the most southernly-known occurrences for Cardabiodon I've seen from North America, if not the Northern Hemisphere. I've heard of at least one another Kansas find.

Jess

P.S. To read up on Cardabiodon:

SIVERSON, M., 1999. A new large lamniform shark from the uppermost Gearle Siltstone (Cenomanian, Late Cretaceous) of Western Australia. Transactions of the Royal Society of Edinburgh: Earth Sciences, 90: 49-66.

here's a link to another article:

https://www.app.pan.pl/article/item/app50-301.html

For info on a Cretoxyrhina dentition:

SHIMADA, K., 1997. Dentition of the Late Cretaceous lamniform shark, Cretoxyrhina mantelli, from the Niobrara Chalk of Kansas. Journal of Vertebrate Paleontology, 17(2): 269-279.

This was found in the upper Greenhorn Limestone of Central Kansas. It seems that there has been quite a bit of confusion between Cretoxyrhina and Cardabiodon over the years. Thought I'd post some pictures so the "shark tooth people" on here could give their opinions.

Ramo

The last photo is the "in-situ" photo when found.

[MikaelS]

Its not a Cretoxyrhina. Cardabiodon occurs relatively abundantly in the Greenhorn (C. ricki in the lower part, C. venator in the upper part and transistional forms in the middle) whereas I have not positively identified the otherwise dentally similar Dwardius from the Western interior Seaway. The very wide neck indicates Cardabiodon rather than Dwardius and so does the absolute size of the tooth (Dwardius laterals are smaller). The profile view suggests Dwardius but I am inclined to suspect that we are dealing with a somewhat aberrant Cardabiodon tooth. Always a bit tricky to identify teeth that:(1) you can't examine first hand; (2) have an incomplete root; (3) are still partly covered in matrix.

[missingdigits]

Awesome. Thanks for the input Doc. It's really appreciated!

[Ramo]

Thanks a ton for the info. I really do appreciate it. I believe that Cardabiodon is probably more common in KS than most people think.

Ramo