Calvert FM - Mammal Skull Find?

[Vae70]

Hi TFF, I found a small skull walking the beach at Flag Ponds this morning. It measures about 3" long and 2" wide, thinking some sort of small mammal based on the font teeth. The skull is quite heavy and fits the same color/weight/texture of the numerous bone fragments found in the area. Images edited to show further detail, would appreciate help with an ID

 

In situ: 

 

Close-ups

[Coco]

Rabbit ! I mean, I think, because your skull looks wet, it shines a lot. How big is it ?

 

Coco

Edited September 29, 2023 by Coco

[Vae70]

It is still drying off a bit!

[Coco]

Compare with this skull almost at the bottom of the page https://www.zoom-nature.fr/les-lapins-ne-sont-pas-des-rongeurs/

 

Coco

[patelinho7]

Hmm. Interesting that it’s the same color as other fossilized bone.

[jpc]

Allo coco and vae70-- not a rabbit.  Rabbits have fenestration in front of the eyes as seen in this photo from the web site linked.  Also they have a second set of incisors behind the main front teeth that this guy does not have.  

 

 

The skull is a rodent and it should be identifiable with some research by the few teeth in it.  

 

Can we see a front view?  How big is the hole on the front edge of the zygomatic arch?  Porcupines have a huge hole there and are the only ones to do so.  

Edited September 29, 2023 by jpc

[Vae70]

35 minutes ago, jpc said:

Allo coco and vae70-- not a rabbit.  Rabbits have fenestration in front of the eyes as seen in this photo from the web site linked.  Also they have a second set of incisors behind the main front teeth that this guy does not have.  

 

 

The skull is a rodent and it should be identifiable with some research by the few teeth in it.  

 

Can we see a front view?  How big is the hole on the front edge of the zygomatic arch?  Porcupines have a huge hole there and are the only ones to do so.  

Here are some more shots, hope they help!

[jpc]

the hole there is not big enough to be a porcupine.  And the teeth are not beaver.  The last photo is great shot of the teeth... look into muskrat.  But then at Calvert cliffs, the question is always is this fossils, and what sorts of rodents are known from the Miocene of this area?  

 

Compare the teeth to these:

https://www.wtamu.edu/~rmatlack/Mammalogy/ondatra_skull.htm

 

 

[Vae70]

I think Muskrat is correct based on the looping teeth. I cannot find reference to any rodent examples from the cliffs but have reached out to the calvert county marine museum

[jpc]

also the angle of the zygomatic arch in the nose-on view is pretty muskratty on yours.  

[ClearLake]

Very definitely a muskrat (Ondatra zibethicus).  I would not rule out modern, unless this is how fossil skulls from this formation appear.  

 

Here is a brief snippet from Scientific American Blog:

 

Hundreds of fossil Ondatra specimens are known, extending back in time more than 4 million years to the Lower Pliocene. Martin (1993) and some other authors have argued that these all belong to the same single lineage and that they essentially represent different ‘chronomorphs’ of O. zibethicus (formerly, as many as six species were identified, as was the distinct genus Pliopotamys). Not everyone agrees with the taxonomy that Martin employs, of course: the name Pliopotamys is still used by some, and species distinct from O. zibethicus are also still recognised by some authors. Chaline et al. (1999), for example, recognised O. obscurus for an isolated muskrat population from Newfoundland.

 

A brief history of muskrats - Scientific American Blog Network

[Vae70]

28 minutes ago, ClearLake said:

Very definitely a muskrat (Ondatra zibethicus).  I would not rule out modern, unless this is how fossil skulls from this formation appear.  

 

Here is a brief snippet from Scientific American Blog:

Hundreds of fossil Ondatra specimens are known, extending back in time more than 4 million years to the Lower Pliocene. Martin (1993) and some other authors have argued that these all belong to the same single lineage and that they essentially represent different ‘chronomorphs’ of O. zibethicus (formerly, as many as six species were identified, as was the distinct genus Pliopotamys). Not everyone agrees with the taxonomy that Martin employs, of course: the name Pliopotamys is still used by some, and species distinct from O. zibethicus are also still recognised by some authors. Chaline et al. (1999), for example, recognised O. obscurus for an isolated muskrat population from Newfoundland.

 

A brief history of muskrats - Scientific American Blog Network

Thank you!

 

After it dried, I did try a small burn test which did not give off the telltale "collagen burning" aroma I get with mystery bones from the NJ books. I can't find much on the coloration of specifically redeposited skulls from this fm as almost all bone is turned into fragments quickly by the ocean, though the color/texture/weight of the skull is consistent with those plentiful bone fragments. Bones and skulls when dug out of the cliffs in original positions tend to be more reddish brown

[fossillarry]

It can't be a rabbit for no other reason than the specimen does not have two sets of upper incisors.

[Coco]

Hi,

 

Well done ! I had only looked at the inner teeth and the lack of quality of the first pictures misled me. I agree with you.

 

Coco