Cretaceous Micro Shark ID

[fossilsonwheels]

I have a few more micro shark teeth from the Mesaverde formation that I need ID help with. 

 

Up first is one of the coolest teeth I found in the micro mix. Roughly 2mm with some very cool looking cusplets. I originally thought it might be a Scyliorhinus tooth but I studied some teeth from other and I think I was wrong about cat shark. I thought maybe a tiny Protolamna but that is just a guess. I am actually pretty stumped. 

 

Any suggestions or thoughts are appreciated. 

[Mike from North Queensland]

Would help to see the other side of the root.

[fossilsonwheels]

20 minutes ago, Mike from North Queensland said:

Would help to see the other side of the root.

Yes it would but I am not going to try and remove it from the matrix. It is tiny and I do not have the skills required.

[fossilsonwheels]

Scyliorhinus tensleepensis is described from the Mesaverde formation so I may just label it as such unless somebody says it is absolutely not a cat shark. I am back to leaning toward that ID myself.

[Mike from North Queensland]

Try a short immersion in vinegar then soak in water as it looks similar to this tooth and the same species has been found in america.

The view on your tooth may just be positional for the root shape but the groove is the give away to the species.

 

Mike

[fossilsonwheels]

On 8/24/2019 at 2:26 AM, Mike from North Queensland said:

Try a short immersion in vinegar then soak in water as it looks similar to this tooth and the same species has been found in america.

The view on your tooth may just be positional for the root shape but the groove is the give away to the species.

 

Mike

I am going to practice that with some of the others fossils from this matrix before I do it with this one but I sure do appreciate the suggestion. Very helpful. Thank you

[siteseer]

We need to start with where in the Mesaverde the tooth was collected as it is hundreds of feet thick.  I have seen it characterized as a group containing formations and as a formation with at least a few members but it appears the latter interpretation is the accepted one.  There was an article by Case (1987) on a selachian fauna from the Teapot Dome Sandstone Member, sites in Washakie County, but that is the only one on sharks from the formation that I know of.

 

However, I don't think that tooth is Scyliorhinus tensleepensis because the crown of teeth that species (based on just two teeth) bear a labial overhang of enameloid with short vertical folds along the base of the crown which your tooth does not feature.  Your tooth is the right size and general shape for Scyliorhinus, but yes as Mike said, we would need to see the lingual face of it to have more to go on.  I don't think you can narrow it down to species in any case.  In fact because S. tensleepensis is based on just two teeth (Case, 1987) and was not compared nor contrasted with other Cretaceoous scyliorhinids known at the time, it could be argued that it should not have been described as a distinct species especially since the genus was considered something of a catch-all even in the 80's.  A  couple of detailed paragraphs are usually written to distinguish a new taxon from known apparent relatives of around the same age.  That was not done for S. tensleepensis.

 

It should be added that Cretaceous syliorhinids are still not well-understood worldwide tending to be represented by relatively few teeth in each deposit in which they occur.  Today, these sharks tend to frequent deepwater environments and they tend to be uncommon to rare in shallow water fossil deposits so they seem to have preferred deeper water in the geologic past as well.  Furthermore, Cenozoic teeth and even modern dentitions (well-documented catches of these sharks being uncommon) are not well-studied either though some researchers have turned toward changing that (see Herman, Hovestadt-Euler, and Hovestadt, 1990).  Cappetta (1987) predicted that many named fossil species assigned to Scyliorhinus would be assigned to other genera after modern dentitions were better-understood.

 

It's an interesting find in any case.

 

Jess

 

 

CAPPETTA, H.  1987.
Chondrichthyes II.  Handbook of Paleoichthyology, Vol. 3B:  Gustav Fischer Verlag, Stuttgart.

 

CASE, G.R.  1987.
A new selachian fauna from the Late Campanian of Wyoming (Teapot Sandstone Member, Mesaverde Formation, Big Horn Basin).  Palaeontographica, Abt. A, 197 (1–3): 1–37, 12 fig., 15 pl., 3 tabl.

 

HERMAN, J. & M. HOVESTADT-EULER, M. & D.C. HOVESTADT,.   1990.
Part A: Selachii. No. 2b: Order: Carcharhiniformes - Familiy: Scyliorhinidae in Stehmann, M. (ed.) Contributions to the study of the comparative morphology of teeth and other relevant ichthyodorulites in living superspecific taxa of Chondrichthyan fishes.  Bulletin de l'Institut Royal des Sciences Naturelles de Belgique, Biologie, 60: 181–230.

[fossilsonwheels]

On 8/25/2019 at 1:52 PM, siteseer said:

We need to start with where in the Mesaverde the tooth was collected as it is hundreds of feet thick.  I have seen it characterized as a group containing formations and as a formation with at least a few members but it appears the latter interpretation is the accepted one.  There was an article by Case (1987) on a selachian fauna from the Teapot Dome Sandstone Member, sites in Washakie County, but that is the only one on sharks from the formation that I know of.

 

However, I don't think that tooth is Scyliorhinus tensleepensis because the crown of teeth that species (based on just two teeth) bear a labial overhang of enameloid with short vertical folds along the base of the crown which your tooth does not feature.  Your tooth is the right size and general shape for Scyliorhinus, but yes as Mike said, we would need to see the lingual face of it to have more to go on.  I don't think you can narrow it down to species in any case.  In fact because S. tensleepensis is based on just two teeth (Case, 1987) and was not compared nor contrasted with other Cretaceoous scyliorhinids known at the time, it could be argued that it should not have been described as a distinct species especially since the genus was considered something of a catch-all even in the 80's.  A  couple of detailed paragraphs are usually written to distinguish a new taxon from known apparent relatives of around the same age.  That was not done for S. tensleepensis.

 

It should be added that Cretaceous syliorhinids are still not well-understood worldwide tending to be represented by relatively few teeth in each deposit in which they occur.  Today, these sharks tend to frequent deepwater environments and they tend to be uncommon to rare in shallow water fossil deposits so they seem to have preferred deeper water in the geologic past as well.  Furthermore, Cenozoic teeth and even modern dentitions (well-documented catches of these sharks being uncommon) are not well-studied either though some researchers have turned toward changing that (see Herman, Hovestadt-Euler, and Hovestadt, 1990).  Cappetta (1987) predicted that many named fossil species assigned to Scyliorhinus would be assigned to other genera after modern dentitions were better-understood.

 

It's an interesting find in any case.

 

Jess

 

 

CAPPETTA, H.  1987.
Chondrichthyes II.  Handbook of Paleoichthyology, Vol. 3B:  Gustav Fischer Verlag, Stuttgart.

 

CASE, G.R.  1987.
A new selachian fauna from the Late Campanian of Wyoming (Teapot Sandstone Member, Mesaverde Formation, Big Horn Basin).  Palaeontographica, Abt. A, 197 (1–3): 1–37, 12 fig., 15 pl., 3 tabl.

 

HERMAN, J. & M. HOVESTADT-EULER, M. & D.C. HOVESTADT,.   1990.
Part A: Selachii. No. 2b: Order: Carcharhiniformes - Familiy: Scyliorhinidae in Stehmann, M. (ed.) Contributions to the study of the comparative morphology of teeth and other relevant ichthyodorulites in living superspecific taxa of Chondrichthyan fishes.  Bulletin de l'Institut Royal des Sciences Naturelles de Belgique, Biologie, 60: 181–230.

The paper by Case was the only one I could find on the Mesaverde too so that was my point of reference. The matrix this came from was from Colorado and the specific information is on my desk at work so I will get that tomorrow. 

That is some fantastic information as usual Jess. Very helpful. I had not found any other Cretaceous Cat Shark teeth so I was pretty excited to find something that resembled a Scyliorhinus. 

I am going to practice up on separating some other fossils from that matrix before I tackle this one as I do not want to mess up with it. We want to talk Cat Sharks with the kids as they are fascinating sharks so hopefully the other side of the tooth tells me what I want to hear lol

I have not found a lot of shark teeth in my life but I have a few interesting ones lol