Ozan Formation Sharks Teeth - Part 2

[ClearLake]

I have a few more teeth that I would like confirmation/correction on my ID's.  These are also from the Ozan Formation (Cretaceous - Campanian) of North Texas, near the North Sulphur River.  The bulk of the small teeth (all less than 7mm) I have picked from the matrix that have cusplets primarily fall into Scapanorhynchus or Cretalamna (with a few other genera, but probably not important here).  The teeth shown below I believe to be one of these two genera, but I am uncertain due to a combo of characteristics, so I am asking for some help in deciding what they are or if they are indeterminate (or if they are something else, that is fine to).

 

The first batch are four teeth that I am waffling between Cretalamna appendiculata or Scapanorhynchus texanus lateral teeth.  The root shape and cusplet shape look more like the other Cretalamna I have (these have the more triangular cusplets I associate with Cretalamna as opposed to the pointier ones I tend to see on Scapanorhynchus), but they definitely have a nutrient groove so I'm uncertain.  What else would/should swing me one way or the other?  Any opinions would be appreciated (even a whole different shark if warranted).

 

 

 

The second batch I think are Scapanorhynchus, but they are much narrower with less flared roots than other anteriors I have.  And they don't look like the symphyseal (or close to the symphesis) teeth that I have seen in publications or discussed on here is some threads.  I suppose I should have shown a comparison, but these are really tiny, skinny teeth relative to other small S. texanus teeth I have.  Thoughts?

 

 

 

 

Thanks for your help.

 

Mike

[ClearLake]

OK, lets try one more tooth (?) that I would like to see if anyone has an opinion about. Same location, etc as the teeth above.   @Al Dente, @ThePhysicist, @fossilsonwheels, @hemipristis, @MarcoSr, @bthemoose@JamieLynn

 

Here is a very small tooth (height =~3mm), or not.  One minute I want to call it a Ischyyrhiza avonicola (or similar species) rostral tooth, the next minute I wonder if it is some sort of dermal spine.  Any thoughts would be appreciated.  Note the fine enamel ridges near the base of the crown, most only go part way up but the two on either side in the detail picture below go almost all the way to the top of the crown.

 

                        

 

Thanks for your help.

 

 

[ThePhysicist]

On 3/28/2023 at 12:17 PM, ClearLake said:

The first batch are four teeth that I am waffling between Cretalamna appendiculata or Scapanorhynchus texanus lateral teeth.  The root shape and cusplet shape look more like the other Cretalamna I have (these have the more triangular cusplets I associate with Cretalamna as opposed to the pointier ones I tend to see on Scapanorhynchus), but they definitely have a nutrient groove so I'm uncertain.  What else would/should swing me one way or the other?  Any opinions would be appreciated (even a whole different shark if warranted).

Presence of the nutrient groove rules out Cretalamna, these are all goblin sand/tiger, I may return to the topic this weekend to see if I can better determine between the two. 

 

On 3/28/2023 at 12:17 PM, ClearLake said:

The second batch I think are Scapanorhynchus, but they are much narrower with less flared roots than other anteriors I have.  And they don't look like the symphyseal (or close to the symphesis) teeth that I have seen in publications or discussed on here is some threads.  I suppose I should have shown a comparison, but these are really tiny, skinny teeth relative to other small S. texanus teeth I have.  Thoughts?

These do look like a mix of "symphyseal" positions, and perhaps intermediate?

 

5 hours ago, ClearLake said:

Here is a very small tooth (height =~3mm), or not.  One minute I want to call it a Ischyyrhiza avonicola (or similar species) rostral tooth, the next minute I wonder if it is some sort of dermal spine.  Any thoughts would be appreciated.  Note the fine enamel ridges near the base of the crown, most only go part way up but the two on either side in the detail picture below go almost all the way to the top of the crown.

Technically speaking, rostral teeth are just giant (modified) dermal denticles. This is a denticle, the question of whether this is from the rostrum or not would require some reading on my part.

[ClearLake]

42 minutes ago, ThePhysicist said:

these are all goblin sand/tiger, I may return to the topic this weekend to see if I can better

Ok, thanks. I will delve into those a bit more. 
 

43 minutes ago, ThePhysicist said:

Technically speaking, rostral teeth are just giant (modified) dermal denticles. This is a denticle, the question of whether this is from the rostrum or not would require some reading on my part

Is that based on the shape of the root?  Is there something in particular I can read?  I’m happy to do that if I have access to it?  Thanks

[MarcoSr]

Looks like a sawfish rostral tooth to me.  But as already said, a rostral tooth is a modified dermal denticle, so it can be very difficult to tell some of them apart.

 

Marco Sr.

[Al Dente]

13 hours ago, ClearLake said:

I want to call it a Ischyyrhiza avonicola (or similar species) rostral tooth, the next minute I wonder if it is some sort of dermal spine.

 

I think these are dermal denticles, not from the rostrum. Case and Schwimmer (1988) in "Late Cretaceous fish from the Blufftown Formation in western Georgia" described the round based denticles as Ptychotrygon rostral spines (first photo below), but that is unlikely since there is no evidence that Ptychotrygon had rostral spines. The same denticle type was identified as Sclerorhynchidae indeterminate in Case, Cook, Kightlinger and Borodin "Middle Campanian Euselachian Diversity of the Southern region of the Atlantic Coastal Plain" (second photo below).

 

 

[ClearLake]

Thank you to @ThePhysicist, @MarcoSr and @Al Dente for your thoughts.  This is what I really enjoy about TFF, those with a lot more experience than myself willing to share their thoughts on some of the less obvious ID's.  When it comes to sharks (and their relatives) I just do not have the breadth of experience to recognize items that I have not come across in my very limited shark literature collection or seen in previous posts here.  Some other topics I can hold my own, but not sharks.  Those last couple of illustrations provided above are very helpful for me to see and better understand the nature of the denticles/rostral teeth/whatever other names similar items go by.  I am very happy to label mine as a Sclerorhynchidae denticle and leave it at that until someone can actually find these items associated in a fossil with some oral teeth.  I have found many Sclerorhynchids in this material from at least two different genera so that all makes perfect sense to me but doesn't allow me the confidence of: "well, I've only found XXX species so these must go with that".  Thanks again.

 

Mike

[MarcoSr]

12 hours ago, ClearLake said:

Thank you to @ThePhysicist, @MarcoSr and @Al Dente for your thoughts.  This is what I really enjoy about TFF, those with a lot more experience than myself willing to share their thoughts on some of the less obvious ID's.  When it comes to sharks (and their relatives) I just do not have the breadth of experience to recognize items that I have not come across in my very limited shark literature collection or seen in previous posts here.  Some other topics I can hold my own, but not sharks.  Those last couple of illustrations provided above are very helpful for me to see and better understand the nature of the denticles/rostral teeth/whatever other names similar items go by.  I am very happy to label mine as a Sclerorhynchidae denticle and leave it at that until someone can actually find these items associated in a fossil with some oral teeth.  I have found many Sclerorhynchids in this material from at least two different genera so that all makes perfect sense to me but doesn't allow me the confidence of: "well, I've only found XXX species so these must go with that".  Thanks again.

 

Mike

 

What makes IDs especially tough is when researchers identify specific features in a specimen as different things as Eric points out.  Researchers don't even agree on what to call a denticle in a sawfish rostrum i.e. rostral tooth, rostral spine etc.  Unless you find a fossil that shows the specific specimen in a sawfish rostrum, it is really speculation to claim it is a rostral tooth/spine.  If you look at modern rays, the dermal denticles have an incredible amount of feature diversity.  So there are a good number of dermal denticles that look very similar to actual Cretaceous rostral teeth/spines.

 

Marco Sr.

[JamieLynn]

I finally found my little one that is similar. Also from the Ozan formation. I agree that it's a denticle

 

 

 

 

[Notidanodon]

To add to @ThePhysicists point about the nutrient groove, the cusps on Cretolamna tend to be much more compressed as well  this image online shows it well

Id also be tempted to call 5 and 7 Odontaspis aculeatus

[ClearLake]

23 minutes ago, Notidanodon said:

Id also be tempted to call 5 and 7 Odontaspis aculeatus

Will

Interesting, thanks for the observation.  I'll study that a bit further.

[Mikrogeophagus]

One candidate you may have already looked into for the first four teeth is Carcharias samhammeri which I believe is found in the Campanian. I'm not really familiar with other sand tigers of the Campanian though.

[ClearLake]

17 hours ago, EPIKLULSXDDDDD said:

One candidate you may have already looked into for the first four teeth is Carcharias samhammeri which I believe is found in the Campanian

Thanks, that is not a species I was familiar with.  A quick search tells me that it is like some of the other species, I am probably not qualified to distinguish the various Carcharias/Odontapsis species.  But all the comments have certainly convinced me that the top four teeth belong in one of those two genera most likely.   Scapanorhynchus laterals are still a possibility but I am less inclined to put them there due to the differences with other laterals I have from the matrix.  Welton and Farish have a Carcharias sp A and B that are in the running for some of my teeth as well so I'll probably just have to wait for the next paper (Hamm?) to help sort out these teeth (or just confuse me more ).  

[Mikrogeophagus]

2 hours ago, ClearLake said:

I am probably not qualified to distinguish the various Carcharias/Odontapsis species.

Me neither 

 

All those sand tigers are constantly moving around and being reshuffled across genera, forming new ones, becoming synonymized, etc. A key part of science is acknowledging there are some things none of us fully understand yet. It stinks to not have a clear and confident answer to a question, but in regards to most sand tigers, I think we don't know a lot more than we do.