Three-Toed Horse Tooth

[GPayton]

I found this small lower tooth from a horse a couple weeks back on the Brazos River. Initially, I wrote it off as just another Equus sp. since horse teeth are probably the most common fossil in the Beaumont formation that I hunt in next to turtle shell fragments, but after looking at it again yesterday and comparing it to pictures in Hulbert's book on Floridian fossil vertebrates, I'm starting to rethink my earlier identification. For one, the design of the occlusal surface doesn't match those of ordinary Equus teeth. The tooth I have is an m3 I believe, and comparing it to examples of Equus m3's shows this discrepancy quite well. The tooth is also very small, despite the roots having been worn off a long time ago - the crown length is exactly 2 cm and its width is 0.5 cm. 

I know that pre-Equus horse fossils can be found in the Brazos now after just having an astragalus I found identified as such, and after seeing @Lorne Ledger's very nice upper molar from a Nannippus pulled from the same stretch of the Brazos that I hunt. It's definitely within the realm of possibility. Any help would be appreciated! 

 

[Coco]

Please put your photos directly posted on the forum. Your 1st link crashed my computer !

 

Coco

[GPayton]

Very sorry about that @Coco! Usually I have no trouble posting the pictures directly without using links, but this time they wanted to give me some trouble. The problem should be fixed now. 

[Darktooth]

I think this may be bovine. But I am no expert.

[Lorne Ledger]

Yep agree, it looks like a little horse tooth to me, prolly nannippus

 

[Shellseeker]

13 hours ago, GPayton said:

I found this small lower tooth from a horse a couple weeks back on the Brazos River. Initially, I wrote it off as just another Equus sp. since horse teeth are probably the most common fossil in the Beaumont formation that I hunt in next to turtle shell fragments, but after looking at it again yesterday and comparing it to pictures in Hulbert's book on Floridian fossil vertebrates, I'm starting to rethink my earlier identification. For one, the design of the occlusal surface doesn't match those of ordinary Equus teeth. The tooth I have is an m3 I believe, and comparing it to examples of Equus m3's shows this discrepancy quite well. The tooth is also very small, despite the roots having been worn off a long time ago - the crown length is exactly 2 cm and its width is 0.5 cm. 

I know that pre-Equus horse fossils can be found in the Brazos now after just having an astragalus I found identified as such, and after seeing @Lorne Ledger's very nice upper molar from a Nannippus pulled from the same stretch of the Brazos that I hunt. It's definitely within the realm of possibility. Any help would be appreciated! 

 

In measurements of Tridactyl Horse teeth, the most important measurement is the anterior posterior length (APL) of the chewing surface. In your case , 20 mm.

In Florida , I have found Nannippus peninsulatus, Nannippus aztecus, and Nannippus morgani.  Your Nannippus species in Taxas are different. Here is a comparison of lower left m3's for peninsulatus and aztecus.

[GPayton]

Thanks for the help guys, but I think I just solved it! I was reading up on some of the papers that have been published that describe the dentition of Gulf Coast tridactyl horses in detail, specifically this one: http://digitallibrary.amnh.org/handle/2246/997. There are some very nice and very detailed illustrations of the dentition charts for Nannippus, Hipparion, Cormohipparion, and Neohipparion, amongst others. After comparing my tooth to each of the known Nannippus species, which I was sure had to be the right ID, I found that it didn't really match any of them. The shape of the entoconid was always just slightly wrong, since my tooth has an extra wrinkle or two in the occlusal surface in that spot. However, the m3 for Cormohipparion goorsi was a perfect match. Even better, the species is only known from the Gulf Coast of Texas, and the type specimen was collected just 30 minutes from where I live! Here's a screenshot I took of the relevant dentition chart: 

I'm sure lots of other forum members could use the paper to ID some of their own tridactyl horse teeth if they haven't already found it online for themselves. I know I'll definitely be keeping it bookmarked for referral in the future. 

[siteseer]

Larry should take a look.  @fossillarry