Two Cretaceous Shark Teeth -- Russia and Texas

[bthemoose]

I recently acquired two Cretaceous lamniform shark teeth that I'm trying to identify. The first one, from Russia, was sold as Cardabiodon sp., but I'm curious if that's correct or if it's something else. The second tooth, from Texas, didn't come with an ID. Thanks in advance for any help you can provide!

 

#1 - Cardabiodon? sp.

This tooth is from the Cenomanian of Russia and was found near Fedorovka Village, Tambov Region. The tooth measures 28.51 mm on the slant and 14.91 mm at its widest across the root.

 

 

 

 

#2 - Unidentified

This tooth is from the Lake Waco Spillway in Texas, from the Del Rio Formation, which I believe is Albian in age. The tooth measures 15.93 mm on the slant and 11.15 mm at its widest across the root.

 

 

 

Edited August 13, 2021 by bthemoose

[bthemoose]

@siteseer @Anomotodon @ThePhysicist, do any of you have thoughts on these, perhaps? I’m currently thinking Cretoxyrhina denticulata for the Russian tooth and C. vraconensis for the Texas one.

[ClearLake]

Well, I'm no expert in identifying shark teeth, that's for sure, but in looking through "Fossil Sharks and Rays from the Cretaceous of Texas", I would call it Cretolamna appendiculata which I know are found at that site.  The root interlobe area seems a bit more squared in your specimen but the discussion mentions that in the upper teeth.  Just my two cents.

[ThePhysicist]

I'm fairly sure these are both anterior Cretoxyrhina. I'm less familiar with C. vraconensis and C. denticulata. Siversson et al. (2013) says that for C. vraconensis "most anterior teeth have either a demarcated heel or a cusplet on one or both sides of the cusp." I need to do some more reading before I can say definitively, but it looks like C. vraconensis for both. 

 

[bthemoose]

1 hour ago, ThePhysicist said:

I'm fairly sure these are both anterior Cretoxyrhina. I'm less familiar with C. vraconensis and C. denticulata. Siversson et al. (2013) says that for C. vraconensis "most anterior teeth have either a demarcated heel or a cusplet on one or both sides of the cusp." I need to do some more reading before I can say definitively, but it looks like C. vraconensis for both. 

 

Thanks for the publication! C. vraconensis does look like a pretty good fit for both. 

 

2 hours ago, ClearLake said:

Well, I'm no expert in identifying shark teeth, that's for sure, but in looking through "Fossil Sharks and Rays from the Cretaceous of Texas", I would call it Cretolamna appendiculata which I know are found at that site.  The root interlobe area seems a bit more squared in your specimen but the discussion mentions that in the upper teeth.  Just my two cents.

 

Thanks for taking a look -- Welton and Farish is a great reference! Cretalamna tend to have pretty distinctive cusplets vs. the flattened heels on these teeth.

[ClearLake]

1 hour ago, bthemoose said:

Thanks for taking a look -- Welton and Farish is a great reference! Cretalamna tend to have pretty distinctive cusplets vs. the flattened heels on these teeth.

No problem, always happy to throw out a half-baked opinion!  Haha. I just figured the cusplets on yours were broken or eroded. Walton and Farish does not have C. vraconensis so I’ll have to look at the reference cited for my education. Always good to learn something new. 

[Anomotodon]

Sorry, did not notice this topic before. I agree that both teeth are C. vraconensis; C. vraconensis, C. denticulata, C. agassizensis and C. mantelli are just chronospecies with the first three restricted to Upper Albian- Early Turonian. There is also a lot of stratigraphic overlap between published descriptions of these species, for example C. mantelli is known from Upper Cenomanian... I haven't seen any publications more recent than Siversson et al., 2013 (cited by @ThePhysicist above) discussing C. denticulata in detail, however, it seems that there are issues with its taxonomic status as well. 

 

Although there is this interesting read that suggests that Cretoxyrhina-Macrorhizodus-Isurus are a single evolutionary lineage (ghost lineage in Campanian-Paleocene interval) and therefore all of the aforementioned species should be in the genus Isurus...

[Anomotodon]

On 8/14/2021 at 9:29 PM, ClearLake said:

No problem, always happy to throw out a half-baked opinion!  Haha. I just figured the cusplets on yours were broken or eroded. Walton and Farish does not have C. vraconensis so I’ll have to look at the reference cited for my education. Always good to learn something new. 

 

Actually - in the Cretolamna reconstructed dentition from Welton & Farish second upper anterior is Cretoxyrhina vraconensis and possibly a couple other teeth

[bthemoose]

Thanks for taking a look @Anomotodon, and for your confirmation of the C. vraconensis ID! That’s an interesting paper you linked to as well. I wasn’t aware of Isurus (or whatever the correct genus may be) schoutedeni. Another species to add to the list… 

[ClearLake]

9 hours ago, Anomotodon said:

 

Actually - in the Cretolamna reconstructed dentition from Welton & Farish second upper anterior is Cretoxyrhina vraconensis and possibly a couple other teeth

Great info, thanks. I’ll make a note in my book when I get back home and read that paper. Who knows, maybe I have some C. vraconensis intermixed in my other forms. 

[MikaelS]

On 8/25/2021 at 12:12 PM, Anomotodon said:

 

 

Although there is this interesting read that suggests that Cretoxyrhina-Macrorhizodus-Isurus are a single evolutionary lineage (ghost lineage in Campanian-Paleocene interval) and therefore all of the aforementioned species should be in the genus Isurus...

Good articles are referenced frequently. Those that are not that great are referred to on the odd occasion. Then we have the really bad ones, where the author finally manages to find a journal that will accept it.