Oregon Fossil Teeth ID (Horse?)

[GeoJ]

Hello, I found some fossil teeth on a friends ranch in Eastern Oregon and was hoping for some help with ID. The area has been described as Mascall Formation (16 Ma) from the Miocene, however there aren't any detailed geologic maps of the region and I suspect some areas may be closer to the Pliocene. The teeth were found as float material from several places. I think #1 or #2 may be Merychippus or Pliohippus (horses) and #4 may be Equus (horse). #1-3 were all found in the same general area and I am fairly confident it is Mascall Fm (Miocene). However, #4 was found in another area and appears to be Equus. Since Equus is from the Pliocene, I am thinking it could be from the younger (Pliocene) Rattlesnake Fm or an undescribed strata. I am a little more unsure about #3 and think I could be a rhino or similar large mammal. Thank you for your help,

[Meganeura]

4 Looks to definitely be Equus, and 1 reminds me very closely of the Nannippus found here in Florida, also from the Miocene. agreed that 2 is also horse, but i'm not sure what. And at least for me personally, 3 will probably require some more pics to ID!

[PaleoNoel]

I believe 3 is likely a fragment of rhino tooth. 

[siteseer]

@fossillarry

[Brandy Cole]

Number One looks more like camel to me. 

 

Number Two looks like bison.

 

No clue on Number Three.

 

Number Four may be pre equus if I'm seeing an isolated protocone there.

 

I agree that clearer pictures of the biting surfaces would help a lot with these.

Edited July 24, 2022 by Brandy Cole
Left out important description

[Harry Pristis]

All horse, with the possible exception of #3 which apparently is severely damaged.

[siteseer]

I think #1 could be a Merychippus lower tooth.  I should add that many species once assigned to Merychippus have been reassigned to other genera.  Merychippus is known from the Mascall Formation.

 

Tooth #2 looks like a Merychippus upper tooth.  It's shorter than later hipparion-type teeth and I don't think it's because of a lot of wear. 

 

Yeah, #4 is a more recent horse but it might be something from the Late Miocene.  It seems too curved to be Equus.  Larry will take a look.

[fossillarry]

Number 1 and 2 are Acritohippus isonesus. Number 4 appears to be over 50 mm in crown height, taller then any merychippine genus. Unfortunately the occlusal surface is to unworn to be certain about its pattern. While the protocone is slightly worn I can't tell if there is an anterior spur or not. If it was found in the same vicinity and same strata as the Acritohippus teeth  which is around Early Barstovian then my only guess is that it could be "Merychippus "coloradense. which has not been been found in Oregon before.  I believe number 4 is to shot to be any species of Equus.