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Opabinia Blues

White River Formation small incisors - Rodent? Lagomorph?

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Opabinia Blues

Hello! This is a small fossil from the White River Formation of Weld County, Colorado. To me it appears to be a set of front incisors rooted to a small piece of the maxilla or mandible. There are no teeth or tooth sockets next to the two that are there, and so this makes them look like the two incisors characteristic of rodents and lagomorphs. Interested if anyone can tell me anything else about them.

 

Two photos are through a stereo dissecting microscope at 20X magnification, the other two, though blurry, should give a sense of scale. The entire fossil is about 9 mm tall, with the tooth crowns themselves being about 4 mm tall.

 

224505D2-28FD-4891-AFCE-A26724AAF357.thumb.jpeg.b60c69030b0a19bc860cfc0955802219.jpeg
 

Thanks!

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Top Trilo

The not zoomed in photos look modern but it’s probably just the lighting. I don’t know what it is but a rodent would probably be a good guess

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Opabinia Blues
2 minutes ago, Top Trilo said:

The not zoomed in photos look modern but it’s probably just the lighting. I don’t know what it is but a rodent would probably be a good guess

Thank you! It is just the lighting, I assure you this is a fossil, you’ll have to take my word for it though. I have a little bit of experience with White River fossils and have collected quite a bit from this location. I didn’t even realize it was a little piece of jaw with teeth until I got back, assumed it was a little bone fragment like the many others I pick up.

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Huntonia

A picture of the chewing surface would help greatly in determining a definitive ID

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Opabinia Blues
10 minutes ago, Huntonia said:

A picture of the chewing surface would help greatly in determining a definitive ID

This appears to be the chewing surface, I hope it is clear enough.

 

B316D1C3-F627-4220-849D-D6B5C31AE763.thumb.jpeg.3da0abd449496f195d8ff553dc403954.jpeg

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Opabinia Blues
13 minutes ago, Huntonia said:

A picture of the chewing surface would help greatly in determining a definitive ID

Unless you meant the top surface, sorry about that potential misunderstanding. Here’s the best magnified view I could get of that.

 

827805D5-535E-41F9-9CE5-93E1B8D5079C.thumb.jpeg.dc2c4e34889104c3a2fca333e1395de0.jpeg

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Top Trilo
1 hour ago, OpabiniaBoogaloo said:

I assure you this is a fossil, you’ll have to take my word for it

I believe you, I just don’t have enough experience to ID it. I hope we find out what it is though, good luck

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Huntonia

Looking at this I believe you don't have an incisor at all, but rather a section of a lower jaw with a tooth in it. Not sure exactly what from, maybe a rabbit or some kind of rodent. Perhaps @jpccan assist us. Below is a picture of a Palaeolagus lower jaw to demonstrate the section I believe you have.

20200920_205758.jpg.04263d67ba204e83c7c0b693a55a0b79.jpg

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Opabinia Blues
36 minutes ago, Huntonia said:

Looking at this I believe you don't have an incisor at all, but rather a section of a lower jaw with a tooth in it. Not sure exactly what from, maybe a rabbit or some kind of rodent. Perhaps @jpccan assist us. Below is a picture of a Palaeolagus lower jaw to demonstrate the section I believe you have.

20200920_205758.jpg.04263d67ba204e83c7c0b693a55a0b79.jpg

Thank you! That actually makes a lot of sense looking at that view.

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Opabinia Blues

@jpc any thoughts on this one?

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jpc

I just saw this... Huntonia has got it.  This is a Paleolagus lower jaw frag... premolar or molar, not incisors.  I am not sure of the dental formula for rabbits.  

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Coco

@jpc recent rabbit bottom : PM1 - PM2 - M1 - M2 - M3 (Perhaps I have to write pm1 - pm2 - m1 - m2 - m3 ?).

 

Coco

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jpc
29 minutes ago, Coco said:

@jpc recent rabbit bottom : PM1 - PM2 - M1 - M2 - M3 (Perhaps I have to write pm1 - pm2 - m1 - m2 - m3 ?).

 

Coco

Thanks, coco.  So this fossil is the jaw fragment with lower first premolar.  I think that is one tooth, as opposed to first and second premolars, but anyone else feel free to correct me.  

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Coco

I have forgoten "I", but I don't think they are important here :oO:

 

 

Coco

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ParkerPaleo
25 minutes ago, jpc said:

Thanks, coco.  So this fossil is the jaw fragment with lower first premolar.  I think that is one tooth, as opposed to first and second premolars, but anyone else feel free to correct me.  

It is a single tooth, p1.  I was too slow to the ID party :)

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jpc
57 minutes ago, Coco said:

I have forgoten "I", but I don't think they are important here :oO:

 

 

Coco

Actually, coco, one of the distinguishing characters of rabbits is two upper incisors.  No rodent has this.  Rabbits have a small incisor behind each main front upper teeth.  Also, there are zero canines.  

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