Calvert Fm (Miocene) Bone

[historianmichael]

I collected this bone earlier this week in an outcrop of the Calvert Formation (Early-Middle Miocene) in Maryland. I found several vertebrae in close proximity to each other that I have tentatively identified as dolphin. I will share them after I finish cleaning and prepping them. Next to one vertebra was this mystery bone. Any idea what it could be? Maybe part of the dolphin sternum? Any help would be greatly appreciated.

 

[cck]

Looks like a worn cetacean axis vertebrae.

[cck]

For comparison

[historianmichael]

Thank you. This was found in-situ. Tells a story about how worn down the bone got before it was buried and fossilized.

[historianmichael]

I collected all of these vertebrae from about a 10-15 foot section of a creek exposure of the Calvert Formation. I suspect that they are all dolphin and from the same individual, but I was hoping to get some confirmation from collectors who are more experienced with Miocene cetaceans. Are these from a dolphin and is it likely that they are from the same individual? What I thought was interesting was that most of the vertebrae have fused end caps, but two are missing the end cap on one side. I know that vertebrae are not diagnostic to species, but is there a way to tell what family of dolphin these bones likely came from? 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[MJ2492]

Nice finds!

 

Based on the variation in size and position of the vertebrae I would be hesitant to say that they're all associated. Though, to find that number in a short area could certainly mean some are associated. Especially if some were very close together.

 

I wouldn't be confident giving any species or genus, but they are all certainly in the right size range to be from odontocetes. Given the size if the first six I would guess that they most likely came from Eurhinodelphinids of some sort just going on how overwhelmingly common they are amongst the Odontocetes found in the lower Calvert Group. Though the seventh vert may be from a Kentriodontid of some kind going off of the smaller size and fused epiphyses.

 

If you'd like to learn a bit more about odontocetes from the Calvert Group, I'd highly recommend the second volume of The Geology and Vertebrate Paleontology of Calvert Cliffs. The Geology and Vertebrate Paleontology of Calvert Cliffs, Maryland, USA – Volume 2: Turtles and Toothed Whales - Smithsonian Institution Scholarly Press (si.edu)

 

Also to throw my hat into the ring, I think the piece you started the thread with may be a worn dolphin thoracic or lumbar vertebra. It looks like the transverse and spinous processes have worn off, either due to rework or maybe sitting on the sea floor for a while before fossilization.