Ozan Formation polycotylid plesiosaur tooth fragment

[pachy-pleuro-whatnot-odon]

Hi all,

 

I got this partial tooth in last week which I bought from a US-based seller claiming it was a mosasaur tooth - though I bought it already suspecting it is not. Having since received the specimen, I can confidently say it's plesiosaur, more than likely polycotylid, as the ornamentation exhibits dense packing of fine striations lingually and a near complete drop-off of striae labially with only some small ones remaining near the base of the crown at great intervals. In a lot of ways this type of ornamentation is reminiscent of that of Jurassic pliosaur teeth. But as the tooth is said to have come from the Ozan Formation, which dates to the Campanian and Maastrichtian and therefore a time after pliosaurs had gone extinct, it's obviously not possible for the tooth to be pliosaur. It's morphology would moreover be somewhat strange for a brachauchenine pliosaur, as the striations are indeed very fine. Cross-section of the tooth is sub-circlular without carinae but with a slight lingual curvature.

 

Now my question here would be if anyone knows what species this tooth might be attributable to. From my own experience identifying Jurassic pl(es)iosaur teeth I know this can be quite a challenge, but also know that there's often some minute indicators that can still help do so anyway. My current candidates, based on regional occurrence and time-bracketing would be Dolichorhynchops and Polycotylus. I, however, lack the proper geological and geographical resolution to narrow genus or species ranges down further.

 

@JarrodB @Jared C @JohnJ @Jackson g (and anybody else who might be able to help out)

 

[pachy-pleuro-whatnot-odon]

I realise I haven't mentioned the sizes yet: the base is 16.5 x 15mm; the top, where it's broken off 11.6 x 11.3mm; and the preserved part of the crown measures 21.5mm, or 23.6mm with root.

[Jared C]

I can't help out unfortunately, as I don't know much about plesiosaurs. But, I'm following with keen interest, since they're much more uncommon in the Ozan here. In all my Ozan excursions, I've only ever found one identifiable trace of a plesiosaur, and that was a caudal rib fragment. A tooth is super cool 

[pachy-pleuro-whatnot-odon]

6 minutes ago, Jared C said:

I can't help out unfortunately, as I don't know much about plesiosaurs. But, I'm following with keen interest, since they're much more uncommon in the Ozan here. In all my Ozan excursions, I've only ever found one identifiable trace of a plesiosaur, and that was a caudal rib fragment. A tooth is super cool 

 

Thanks! Yeah, when I spotted this tooth and plioplatecarpine mosasaur one for sale from the same seller, I knew I didn't have time to hesitate, as such teeth are always in great demand. But especially when I noticed the striations, I knew there was a good chance of this being plesiosaur and therefore much rarer. In fact, this is only my third US plesiosaur/polycotylid tooth, and the first from the Ozan. The fact that most of the ornamentation was still hidden by clay/matrix probably meant it didn't move as fast as it otherwise would have, allowing me to pick it up. But I was very excited when the tooth finally arrived and my suspicions turned out to be correct! I mean, I've seen quite a number of plesiosaur vertebrae from the Ozan and NSR come by here on the forum (e.g., the one that @Roz found or those in @Foshunter's collection, below), but don't think I've ever seen a tooth...

 

 

[pachy-pleuro-whatnot-odon]

On 4/7/2022 at 5:09 PM, pachy-pleuro-whatnot-odon said:

 [...] but don't think I've ever seen a tooth...

 

Well, seems memory failed me there, as there's this beautiful chance find @bluefish1766's kids made