Polyacrodus

[readinghiker]

Out of over 17,000 teeth pulled out of ant hills in north central New Mexico, I came up with this one isolated tooth.

There are a scattering of other hybodontids in the fauna, but this is the only one of this kind.  I originally thought this

was Polyacrodus parvidens, but upon getting into the literature I have discovered that this species has a high central cusp

and the ornamentation isn't as strong as that on this tooth.  So now I am leaning to P.  cf. brevicostatus, and if this is the 

case, would be one of the first examples from this state.  Any ideas from all of the distinguished people on the Forum?

[jpc]

age?  

 

So are you saying you have collected 17K teeth and that this one is different?

 

 

[readinghiker]

JPC...

 

  This is Coniacian.  And yes, out of over 17,000 teeth screen washed from ant hills, this is the only Polyacrodus.  I also found one fossil

mammal incisor as well.  The vast majority of the teeth were Scapanorhynchus raphiodon  and Cretolamna sp.  There was also a new

ptychotrygon that will be named when this fauna is published, as well as the second New Mexico occurrence of the Scindocorax genus.

I have been working on these suckers for over three years, and the end is yet to come into sight.  In fact, on February 18 I will be going back

out to the site with the New Mexico Museum of Natural History and Science (of which I am a research associate) to try and find some of these

teeth in the matrix, rather than letting the ants do all of the work!

[Fossildude19]

@jdp

[The Amateur Paleontologist]

Sounds quite exciting Keep us updated!

[siteseer]

It's a partial tooth so it's tough to be definite (and I'm not a "hybodont guy" although I've had opinions on Asteracanthus before) but I think that's a Polyacrodus parvidens lateral tooth which would have a lower main cusp and also more prominent crown ridges and more distinct cusplets that distinguish that species from others.  P. brevicostatus tends to have finer ridges and rather irregular cusplets.

 

 

[jdp]

It miiight be, but my first impression of this is that this is a malformed dermal denticle.

[Kato]

23 hours ago, readinghiker said:

Out of over 17,000 teeth pulled out of ant hills in north central New Mexico, I came up with this one isolated tooth.

There are a scattering of other hybodontids in the fauna, but this is the only one of this kind.  I originally thought this

was Polyacrodus parvidens, but upon getting into the literature I have discovered that this species has a high central cusp

and the ornamentation isn't as strong as that on this tooth.  So now I am leaning to P.  cf. brevicostatus, and if this is the 

case, would be one of the first examples from this state.  Any ideas from all of the distinguished people on the Forum?

Hi, would you kindly post the relative size of this specimen?

 

I guess it has not been on my mind to sit and look at the debris around ant hills but, down here in southern NM, we do have tons of them! Also, I do recall going through northern Nevada and exploring ant mounds looking for small gems. Those ants are sure industrious.

 

Thanks!

[readinghiker]

To JDP,

  I have found several dermal denticles in this and other sites, and they are always a lot smaller and thinner.  This tooth fragment os 6.13 mm long. 2.79 mm wide, and 2.24 mm in height.

In all of the denticles I have found, as well as those in the Museum's collection, I have never seen anything this big or dense,  The reason I thought it was P. parvidens was the similarity to the pictures in Welton and Farrish's Cretateous Sharks of Texas book.  But I am open to all suggestions!

 

To siteseer,

  I am leaning in your direction as to it being P. parvidens.  The reason I questioned this was because this species has a high central cusp. Of all the papers I have looked at, there have been no posterior teeth.  The heterodonty of this species is unknown to me.  The ridges are very thick, like the ones on parvidens.  Also, the secondary cusp is far more rounded than on brevicostatus.  In Welton's book, the central cusp has a slight lingual inclination, and this tooth doesn't.  Do you (or anyone on the Forum) know of a paper or site that I can access that has a picture of a more posterior parvidens tooth?  Thank you for your information!  As always, just about any genus of sharks has its own mysteries and headaches!

 

To The Amateur Paleontologist,

  I need to post more regularly on the Forum.  I will do this more frequently.  After I finish writing up this species, it is on to either the Cantioscyllium or Rhinobatos families.  Out of this fauna, I imagine there will be at least 20+ species.

 

To Kato,

  See my reply to JDP for the measurements of this fossil.  This is the first time anthills have been this productive, at least for me, in New Mexico.  The site is about a mile south of the volcanic plug of Cabezon.  I once went with the Notre Dame field crew to the Fort Peck reservoir in Montana looking for Cretaceous mammals.  We dug up several anthills and found tons of multituberculates!  It was a great time, the hardest part was ignoring the four or five ceratopsians that were eroding out around us.  As Dr. Keith Rigby kept telling us, "We are here for the small stuff!"

[readinghiker]

Still working on this one tooth!  Here is another picture.  As you can see, the vertical folds all connect to a somewhat circular band around the apex of the main cusp.

The band looks to be of the same composition as the folds.  Has anyone seen this feature on any other Polyacrodus teeth?  I am still going back and forth as to whether

this is P. parvidens or P. brevicostatus, but I am leaning heavily towards the former, as brevicostatus displays a lingual bulge when viewed apically, which this tooth doesn't.

Again, thanks for all comments!