Unidentified shark

[readinghiker]

Hey all!  Still working on the Cabezon fauna, which looks to be never ending!  I have, so far, over 16,000 fossils

(mostly selachian teeth) recovered from ant hills.  I just went out yesterday and got another 100 pounds of ant

hill to go through.  Although most of the teeth are scapanorhynchus and cretolamna, there are several other 

species represented, including some very small orectolobids.  I also run across a few that I have not seen in the

literature or in other museum collections, so I am going to post a few this week to pick your brains.  The first one

could be a symphysial of something, but the labial face is different than anything I have seen.  The cusp is almost in

bas relief to the root.  This is not a result of weathering, as the enamel of the cusp turns inward at the base before

it reaches the root.On the lingual face, the root is more pronounced (in the picture of the labial face, you can see the

root reach up to half the crown size).  Any ideas?  And this is just the first of a few I will post.  I have three photos,

so there will be three posts of them.

Thanks!

Randy

 

[readinghiker]

[ThePhysicist]

Lovely tooth. I'm guessing Cretaceous since you mentioned Scapanorhynchus and Cretolamna. I vote Cretoxyrhina sp.

[readinghiker]

Yes, this is Cretaceous.  Cretoxyrhina would be a very good guess, but I am still hung up on the way the base of the crown on the labial face stands out from the tooth.  Here is a photo of the lingual face.

[ThePhysicist]

1 hour ago, readinghiker said:

but I am still hung up on the way the base of the crown on the labial face stands out from the tooth.

Sorry, not sure what you mean by "stands out." Seeing a good dental band/bourlette, I'm more convinced this is a ginsu. I guess there's room for it to be Cretolamna, but I would think there would be indications of cusplets, which I don't see (some cretoxyrhina can also have small cusplets, depending on position and what time period). I think it could be a symphyseal. Here are a couple of ginsu symphyseals for comparison (though these are skinnier, couldn't find a photo of the right position):

[readinghiker]

Cretoxyrhina would be a good bet.  When I stated that the bottom of the crown stands out, I meant that the dental band is very pronounced.

More research to do!  Thank you for heading me in that direction.  I am just plowing into the final 100 pounds of anthill,

and some of the rarer teeth include hybodonts  (which will be no fun trying to sort out), and sawfish oral teeth, which are really tiny.  Then there are the very

rare rhinobatos, just found another of those today.  The work goes on!

[ThePhysicist]

Best of luck! Be sure to share your finds with us! Hybodont and sawfish oral teeth are some of my favorites; I've only found one rhinobatos (male) to date.

[fossilsonwheels]

Helpful post. I have a similar looking tooth to the one @ThePhysicist posted from Cenomanian of Russia. I thought it was Cretoxyrhina so it’s cool to see another one with that ID. 

 

I love Cretaceous micros so I look forward to seeing more of your teeth. There is an a Orectolobiformes collection thread. I’d love to see yours posted there some time ! 

[readinghiker]

I will be posting more as the days progress.  Thanks for your interest!

 

[siteseer]

I've been looking at this tooth the past few days.  I don't think it's a symphyseal because the root lobes are too expanded and rounded.  It's awfully small to be from Cretoxyrhina unless it's from a baby.

 

 

[readinghiker]

As for the size, most of the several thousand teeth from this site are small.  This could be a result of the size of material the ants could use to build up their anthill, or there is a possibility of this being a shark nursery. There are a few large teeth in situ around the anthill, but not many.  There are far more small teeth in situ.  At another site  a couple of dozen miles away, the vast majority are large adult teeth of the various sharks (see New Mexico Museum of Natural History and Science bulletin #52, which is a monograph on this second site, and is available as a free download). If you don't think this is Cretoxyrhina, any idea of what it could be?

 Thanks for your input!