Partial mammal lower jaw-Brule fm.

[Nipponites]

Hello,

I have just received this partial lower jaw, it is supposed to be from Leptomeryx evansi, but i have seen many skulls of L. evansi on the internet, and this doesn't look similar. 

It comes from the Oligocene of  Orella member, Brule formation; South Dakota.

I have got three questions;

Who did this jaw belong to?

What part of the jaw did these teeth occupy?

Is that hole on the first photo normal? Or was made by an animal or disease?

 

 

Thanks to everyone!

[Mahnmut]

Hi Nipponites,

I cannot tell you a species, but a bit of anatomy to answer your second and third question.

This looks to be the left and foremost part of a mandibula, or lower jaw. The hole is the foramen mentale, in life the nervus mentalis runs there.

The rough surface in the second pic is the symphysis, it connected to its counterpart on the other half of the mandibula. So the teeth you see broken off in the last pic where the incisivi (and maybe a canine).

Best regards,

J

[Nipponites]

Thanks Mahnmut, grateful to learn something new.

[jpc]

This is defintely the front end of a left lower jaw lower jaw including the part that connects with the right jaw. It looks like a small oreodont.  Letpomeryx  has a diastema (tooth gap after the incisors which this specimen does not have).  Here is a drawing of Leptomeryx. 

[Nipponites]

Thanks jpc, I have searched all species from Brule formation on the internet, and Leptauchenia decora, a small oreodont as you said, looks quite similar.

 

Here is one from Natural History Museum of Milano:

[ParkerPaleo]

Assuming the stratigraphy is correct, it wouldn't be a Leptauchenia.  They are known from the Whitney/Sharps and above.  I suspect this is most similar to Miniochoerus gracilis.  

 

[Nipponites]

Thank you so much ParkerPaleo for the information, I will take a look at Miniochoerus.

 

 

 

[Coco]

Hi,

 

I think, given the wear on the teeth, it was an old specimen.

 

Coco

[kgbudge]

On 1/6/2022 at 3:56 AM, Mahnmut said:

Hi Nipponites,

I cannot tell you a species, but a bit of anatomy to answer your second and third question.

This looks to be the left and foremost part of a mandibula, or lower jaw. The hole is the foramen mentale, in life the nervus mentalis runs there.

The rough surface in the second pic is the symphysis, it connected to its counterpart on the other half of the mandibula. So the teeth you see broken off in the last pic where the incisivi (and maybe a canine).

Best regards,

J

Right, the distinctive rough surface in the second image is the suture joining the two halves of the mandible. In other words, it's where two bones (the two mandlible halves) grew together in the young animal and fused. This is a point of weakness where fossilized bone will tend to come back apart.