Mammal tooth ID needed. Cretaceous-JRF

[WyomingRocks!]

Hello, I have a number of Cretaceous aged mammal teeth that I would like to ID. Here is one I found recently in the JRF of Montana.

 

I have a hard time taking pics of small teeth but I hope these are good enough for someone to ID it. Thanks for any help!

 

It is about 3 mm wide.

[Fossildude19]

@jpc

[Meganeura]

So I dunno about cretaceous or not - but this looks to me like a raccoon premolar. 

 

[jpc]

Hi WyoRocks-

 

You keep coming up with good stuff in your sites. 

 

I can help you ID this to the subclass.  

Cretaceous mammals 101:

 

There are two things to look for in molars (let's just skip premolars, canines and incisors for now).  Does it have two sets of three cusps like yours?  If so it is a lower molar of either a marsupial or a 'modern' mammal.  Does it have three larger cusps arranged in an triangle?  If so, it is an upper molar of the same two groups. If it is has parallel rows of cusps that are all about the same size, then it is a multituberculate molar.  

 

Cret Mam 102:

See how yours has, again, two sets of three cusps?  Look at the lower ones.  Are all three kinda equal distance apart?  If so (and I think that is what I see in the third photo), then it is an placental mammal (what I call 'modern' above).  If the center one is offset and twinned with one of the others, then it is a marsupial.  With upper molars, if there are a series of small cusplets on the edge, next to the two cusps that are closest together, then it is a marsupial.  

 

Get it? 

 

While we are at it, note that the raccoon premolar does not have two sets of three cusps nor a triangle of three cusps; it has extra cusps that are almost as big as the main three. which is something that we start to see more of in the Paleocene and Eocene.    

 

Meanwhile, you oughta have a look at this:

https://digitallibrary.amnh.org/handle/2246/3575

Click on the 'view/open' link or the little illustration of the paper to see the actual paper. 

In Fig 13 the tooth labeled F, see how the two cusps on the top right corner are nearly on top of each other?  They are twinned.  

Edited November 15, 2022 by jpc

[WyomingRocks!]

@jpc thanks for the help and the document!