Odd Hell Creek Mammal, Eutherian?

[ThePhysicist]

Hi y'all, I came across this odd lower mammal molar from the HCF and I still can't make a more precise determination. It doesn't seem to follow the metatherian tooth design, so I guessed it must be eutherian.  It seems to have only four cusps. Any insight is appreciated, and I can provide more photos if need be. @jpc

Edit: I can't seem to tag people, could someone page jpc?

 

Edited October 18, 2023 by ThePhysicist

[Coco]

@jpc

 

Coco

[jpc]

Here I am.  Referring to your last photo, there is fifth cusp on the talonid (the lower half of the tooth seen in the left half of said photo.  Where your blue line bends along the bottom edge close to the leftmost cusp.  This is a a marsupial (metatherian) characteristic.  On the other hand, there are only two cusps on the taller part (the trigonid), and that is confusing and non-marsupialian.  So, I stand with you... uncertainty rules.  I only checked Lillegraven's Mesozoic mammals book.   there are other sources out there to look at.  

 

Edited October 18, 2023 by jpc

[ThePhysicist]

9 hours ago, jpc said:

Referring to your last photo, there is fifth cusp on the talonid (the lower half of the tooth seen in the left half of said photo.  Where your blue line bends along the bottom edge close to the leftmost cusp.

Okay, I saw that but it's so subdued I didn't consider it one. Here are some more photos, not that it helps the ID:

 

9 hours ago, jpc said:

On the other hand, there are only two cusps on the taller part (the trigonid), and that is confusing and non-marsupialian.  So, I stand with you... uncertainty rules.  I only checked Lillegraven's Mesozoic mammals book.   there are other sources out there to look at.  

Thanks for your input, ya two cusps on the trigonid is odd, it's not broken and doesn't appear pathological? I've so far referenced the publications below, and yet to see something resembling it. I think I'll reach out to a few other professionals to see if it's interesting.

 

* Clemens, William A. Fossil Mammals of the Type Lance Formation, Wyoming. Part II, Marsupialia. University of California Press, 1966.

* Kielan-Jaworowska, Zofia, et al. Mammals from the Age of Dinosaurs: Origins, Evolution, and Structure, Columbia University Press, 2004. 

* Wilson Mantilla GP et al. 2021 Earliest Palaeocene purgatoriids and the initial radiation of stem primates. R. Soc. Open Sci. 8: 210050.
https://doi.org/10.1098/rsos.210050

* Richard C. Fox. 2015. A revision of the Late Cretaceous–Paleocene eutherian mammal Cimolestes Marsh, 1889. Canadian Journal of Earth Sciences. 52(12): 1137-1149. https://doi.org/10.1139/cjes-2015-0113

 

18 hours ago, Coco said:

@jpc

 

Coco

I also can't react to posts, thank you!

[ThePhysicist]

On 10/18/2023 at 8:49 AM, jpc said:

Here I am.  Referring to your last photo, there is fifth cusp on the talonid (the lower half of the tooth seen in the left half of said photo.  Where your blue line bends along the bottom edge close to the leftmost cusp.  This is a a marsupial (metatherian) characteristic.  On the other hand, there are only two cusps on the taller part (the trigonid), and that is confusing and non-marsupialian.  So, I stand with you... uncertainty rules.  I only checked Lillegraven's Mesozoic mammals book.   there are other sources out there to look at.  

I just checked Lillegraven 1969 (linked), and I think it's a dead ringer for Gypsonictops P₄:

 

 

Looks like a pretty interesting phylogeny, being an early eutherian with potential relation to insectivores, rodents, and primates!