More Carmel Church kentriodontids

Next week is the 3rd annual SEAVP meeting. I spent most of this week trying to get my talk ready, so I’ve been taking all kinds of new photos and doing some prep work on a few critical bones that I need for my presentation.

One of these specimens is the large atlas vertebra shown above. This appears to come from a large kentriodontid, dolphin-like odontocetes that were widespread in the middle to late Miocene. It’s fairly similar in size and shape to Hadrodelphis calvertense, which is known from the upper part of the Calvert Formation. While it’s not definitely associated, this atlas was found in the same pit as this large kentriodontid mandible:

I’ve long suspected there was at least one additional kentriodontid at Carmel Church, much smaller than the one shown above, based on several small kentriodontid periotics (earbones):

Last April we collected a tiny tooth that looked like it could be a kentriodontid. Then, going through the collection last week to work on my talk, I came across this atlas vertebrae that was actually collected almost 10 years ago:

Note the difference in scale between this atlas and the one at the top of the page. That enabled me to put together the following slide for my talk:

The idea that we have at least two kentriodontids at Carmel Church looks pretty solid now, even if I can’t yet definitely identify either species.

As always, I’ll be posting a daily summary of the SEAVP meeting.

This entry was posted in Carmel Church odontocetes, Carmel Church Quarry, Chesapeake Group and tagged . Bookmark the permalink.

3 Responses to More Carmel Church kentriodontids

  1. Nice! It does makes good evidence for two different-size kentriodontids. I’m unable to go to the SEAVP this year due to summer job schedule, so I look forward to your post about it!

  2. Tony Edger says:

    Very interesting. Revealing my profound ignorance of these things, what are the telltale signs that this size difference is species related and not related to age or gender of the individuals? The sheer difference in size?

  3. Alton Dooley says:

    A couple of things point to the size difference representing different taxa, and not simply age or individual differences.

    First is the small periotics. Like most vertebrates, whales have anisometric growth, meaning that different parts of the body grow at different rates. Whale earbones, including the periotics don’t seem to vary greatly in size as the animal grows, but these tiny periotics seem to be too small for such a large kentriodontid.

    Second is the fully formed root and tiny crown on the small tooth, indicating that the tooth has reached its maximum size.

    Third is the somewhat different shapes of the atlases. Note how the smaller one has relatively longer and narrower processes and a differently shaped neural canal. This could be due to age-related shape changes, but it’s unlikely. Moreover, although it’s not visible in these images, there are openings (foramina) on the sides of the neural arch that are differently positioned and proportioned on the two specimens. This is less likely to be due to age differences.

    Finally, both these sizes fall within the range of sizes already known for the kentriodontids that have been described based on more complete material. While no small kentriodontid has been described from the upper Calvert, Kentriodon itself is known from the lower Calvert and is about this size.

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