Possible Cetacean Bone ID

[James Savage]

Hello everyone

I have an ID request for the board for these assumed cetacean bones.

These were found diving in a southeastern US river that typically produces Miocene era materials (Megalodon/Hastalis shark teeth, Whale Bulla, Periotics, Teeth, Vertebrae, Assorted Bones) with the occasional Ice Age material (Mammoth/Mastodon teeth and bones).

 

I see these fairly often (about every third dive) but don't typically pick these up.  They have fairly deep grooves on one side (pretty consistently seen in the same pattern) and are pretty flat on another side.  Attached are photos of two that I have kept and couldn't find any info from Googling.

 

Thank you for looking and your opinions.  Let me know if another photo angle may help.

[fossilus]

I've found similar bones in a nonmarine setting and always assumed they were turtle. But the scale looks way off- too large.

Edited August 10, 2021 by fossilus

[fossilcrazee]

@Boesse do you think these are skull fragments?

 

[Boesse]

These are indeed whale skull fragments - the dorsal most part of the squamosal from balaenopterid whales, to be precise - it's usually difficult to see but in your example the "squamosal cleft" (light blue arrows in my image) is the straight side, and it has broken away from the rest of the squamosal.

 

The squamosal cleft is a weird developmental invagination of the squamosal - we have no idea why it evolved.