Oligocene-Era Mammalian Tooth ID Help?

[Piper]

I came across this jaw fragment from a spot in the White River Formation, Central WY.  I'm going crazy trying to ID this thing- any suggestions?

 

 

Edited July 14, 2022 by Piper

[Fin Lover]

Are you able to attach the pics as .jpegs?

[Piper]

4 minutes ago, Fin Lover said:

Are you able to attach the pics as .jpegs?

Done! Thanks for letting me know- HEIC files are a pain in the . 

[Fossildude19]

@jpc  @MarcoSr

[fossillarry]

It's a right lower m3 from Leptomeryx sp. A small early basal ruminant . Nice tooth.

[Harry Pristis]

For comparison:

 

[Piper]

1 hour ago, fossillarry said:

It's a right lower m3 from Leptomeryx sp. A small early basal ruminant . Nice tooth.

Thanks so much for the ID! 

[MarcoSr]

13 hours ago, Fossildude19 said:

@jpc  @MarcoSr

 

The below excerpt is from "Korth Boyd Person Anderson 2022 Fossil mammals from ant mounds situated on exposures of the Big Cottonwood Creek Member of the Chadron Formation latest Eocene early Oligocene Sioux County Nebraska" discussing teeth of Leptomerycids that I donated which came from our M&M Ranch in Nebraska:

 

 

"Discussion—Only two genera of leptomerycids have been reported from the Chadronian and Orellan: Leptomeryx Leidy, 1853, and Hendryomeryx Black, 1978 (see Webb, 1998). The cheek teeth from the Sioux County ant mounds are higher crowned and have more fully developed crests than in Hendryomeryx (Wilson, 1974; Black, 1978; Storer, 1981b; Heaton and Emry, 1996; Webb, 1998). The specimens are small for Leptomeryx, comparable in size to those of the smallest species L. exilis (Table 45) but have smooth enamel on the cheek teeth and lack the well-developed protostyle on upper molars of L. exilis (Cook, 1934; Korth and Diamond, 2002).  All Chadronian species of Leptomeryx and the Orellan type species L. evansi are larger than the ant mounds specimens and can have moderate to heavily crenulated enamel on the molars (Heaton and Emry, 1996). The ant mound specimens also lack the accessory ridge running posteriorly from the apex of the protoconid in the on the lower molars (Palaeomeryx fold) of L. evansi and L. speciosus (Heaton and Emry, 1996: fig. 10; Korth and Diamond, 2002: fig. 1).

The morphology of m3 distinguishs the species of Leptomeryx (Heaton and Emry, 1996: fig. 9). However, there are no m3s referable to Leptomeryx in the ant mound collection likely due to their larger size. In addition, proportions of the referred upper molars in the ant mound collection (longer than wide) differ from that of other species of Leptomeryx where the upper molars are generally equal in length and width or wider than long (Table 45; Scott, 1940: 553; Korth and Diamond, 2002: tables 1, 4). There are only two complete upper molars (M1 or M2) in the ant mound collection (SDSM 156895, 156899). Elsewhere L. exilis has been reported from the Orellan and Whitneyan (Korth and Diamond, 2002)."

 

 

 

From the above discussion, it is clear that for the most accurate ID, you need tooth size measurements and must be able to see all of the tooth features clearly.  Also, to ID the species of a partial Leptomeryx jaw, the jaw must have a good m3.

 

Marco Sr.

[jpc]

Thanks for sharing this latest, marco sr.  I would have simply called it Leptomeryx.