Pathological tooth ID from Bakersfield

[JBMugu]

Hello,

Found this interesting tooth in Bakersfield, in the Round Mountain Silt formation on Dec 24, 2017. To me it looks like a pathological upper tooth from a cow shark (hexanchus). There seems to be a very small inclusion on the side of the tooth (second photo), but hard to say if it was there when the shark lost it. The tooth is about the size of an American penny coin. Any validating comments or ideas are appreciated.

 

 

[ynot]

I agree with the patologic nature of the tooth, but do not think it is hexanchus. (the root looks wrong for hexanchus.)

It looks like 2 teeth have been fused together, possibly symphisael/mesial teeth.

My guess is a Physogaleus contortus.

 

Nice tooth!

[Troodon]

Cool tooth, I agree with your assessment, upper Hex.  No signs of any serrations.

[Tidgy's Dad]

A beautiful oddity. 

I wonder if it caused the shark any problems? 

[ynot]

26 minutes ago, Troodon said:

No signs of any serrations.

Many of the P. contortus I have from there do not have serrations.

[Troodon]

1 hour ago, ynot said:

Many of the P. contortus I have from there do not have serrations.

That was not my rational for calling it hex.  Crowns and root seem to best match hex.  But it's super cool.

[ynot]

17 minutes ago, Troodon said:

That was not my rational for calling it hex.  Crowns and root seem to best match hex.  But it's super cool.

There is a deep separation of the 2 crowns (especially on the labial side) and they are approximately the same size. There is also indications of separation in the root.

 

Lets see what @siteseer, @MarcoSr, @sixgill pete have to say about it.

[sixgill pete]

@ynot @TroodonI have to agree with Frank on this one. I think it is an upper Hexanchus. Possoibly the 2 parasymphyseals fused together.

[Troodon]

8 minutes ago, sixgill pete said:

@ynot @TroodonI have to agree with Frank on this one. I think it is an upper Hexanchus. Possoibly the 2 parasymphyseals fused together.

I think that's the case, the crowns are not attached just the root and the crowns fit.

[MarcoSr]

Can you please give a size of the specimen in millimeters versus "about the size of an American penny"?

 

Marco Sr.

[JBMugu]

Very interesting discussion, thank you guys. The tooth is about 19.2mm by 12.3 mm. Photos attached.

[MarcoSr]

12 minutes ago, JBMugu said:

Very interesting discussion, thank you guys. The tooth is about 19.2mm by 12.3 mm. Photos attached.

 

 

 

Based upon the size and the crown and root features, I would agree that your specimen is Hexanchus.  Your specimen is two upper teeth with a fused root probably as a result of injury or tooth crowding.  You can see the two teeth (in the red oval) in the below JPEG from Compagno 1984 for the extant Hexanchus griseus.

 

 

 

Marco Sr.

[ynot]

OK, I bow to the superior knowledge of Y'all.

Hexanchus.

[JBMugu]

1 minute ago, ynot said:

OK, I bow to the superior knowledge of Y'all.

Hexanchus.

 You hypothesized the tooth being two teeth fused together, I thought it was one tooth that split due to damage/injury. Thank you all for weighing in with your expertise.

[siteseer]

8 hours ago, ynot said:

There is a deep separation of the 2 crowns (especially on the labial side) and they are approximately the same size. There is also indications of separation in the root.

 

Lets see what @siteseer, @MarcoSr, @sixgill pete have to say about it.

 

Hi Tony,

 

That's a weird one alright.  I haven't seen anything similar from STH before.  I can see it as a Hexanchus tooth but I also wonder if it could be two small odontocete teeth fused together.  The crowns look more short and conical like a whale tooth than you would see in a Hexanchus cusp.  Small odontocete teeth can have bent tips though not to the extreme as seen in the photos.  Pathologic Hexanchus teeth are quite rare and of those most have just a twisted cusp.

 

The only other thing I could think of was Hemipristis parasymphyseals but I would expect them to be longer relative to the height if the root.

 

Jess

 

[Al Dente]

It might be Hexanchus but the cusps are not as long or pointed as ones I've seen online. An alternative could be Cetorhinus huddlestoni. The shape of the crown looks right but this fossil would be close to maximum size for C. huddlestoni.

[MarcoSr]

4 hours ago, Al Dente said:

It might be Hexanchus but the cusps are not as long or pointed as ones I've seen online. An alternative could be Cetorhinus huddlestoni. The shape of the crown looks right but this fossil would be close to maximum size for C. huddlestoni.

 

Eric

 

Cetorhinus was my first thought based upon the crown features.  However, that is why I asked about the size of the specimen.  I have several hundred Cetorhinus teeth from STH with the largest only 7mm.  This specimen is almost 3 times that size.  Look at the size of the holotype in Welton's  2014 paper.

 

 

 

 

EDIT: Also from 2014 Welton paper:

 

 

 

See the size of C. maximus teeth from Ebert 2013.

 

 

 

 

 

Marco Sr.

Edited December 26, 2017 by MarcoSr
added rational

[MarcoSr]

4 hours ago, siteseer said:

 

Hi Tony,

 

That's a weird one alright.  I haven't seen anything similar from STH before.  I can see it as a Hexanchus tooth but I also wonder if it could be two small odontocete teeth fused together.  The crowns look more short and conical like a whale tooth than you would see in a Hexanchus cusp.  Small odontocete teeth can have bent tips though not to the extreme as seen in the photos.  Pathologic Hexanchus teeth are quite rare and of those most have just a twisted cusp.

 

The only other thing I could think of was Hemipristis parasymphyseals but I would expect them to be longer relative to the height if the root.

 

Jess

 

 

Jess

 

I also thought about Hemipristis.  However Hemipristis has a toothless gap at the jaw mid-line which separates what I call the medials (you call parasymphyseals) and Hemipristis is not a common species from STH.  Although I too was expecting different crown features, see the below Hexanchus griseus dentition from J-elasmo. With the specimen being pathological and with the wide variation of these first two teeth in the upper dentition the crown features of this specimen seem very possible.

 

 

Marco Sr.