Fossil turtle soup

Sea turtle bones are relatively common discoveries at Carmel Church. More specifically, we commonly find fragments of the the carapace (upper shell), almost all of which belong to a small, extinct turtle called Syllomus. While we’ve probably found over 100 carapace fragments, we don’t commonly find any other parts of the skeleton. For many years, we had three or four vertebrae, and that was it. But in 2002 Bryce Harrison found our first fragmentary turtle humerus, shown above.

Only the proximal end of the bone is preserved, but it was still enough to attempt an identification. Surprisingly, using Weems (1974) as a guide, it turned out to not be Syllomus. Instead, it was most similar to another Calvert Formation sea turtle, Procolpochelys, which we had not previously found at the site. (Since then, we’ve found a few possible Procolpochelys plates.) So we had the unusual situation of having a very common turtle species represented by hundreds of shell fragments but no humeri, and a second species represented only by a humerus.

That’s pretty much where things stayed until 2011, when Drew Moore and Amanda Smolinsky found this more or less complete humerus:

Unlike our first humerus, this one was pretty clearly Syllomus; among other differences, the mid-shaft protuberance is located more proximally in Procolpochelys.

A few months later, Ward Littlefield pulled this bone out of the jacket containing “Picasso’s” vertebral column:

It took awhile to get around to doing the detailed prep work on this bone, but last Thursday I finally had a chance to look at it and it’s also Syllomus, albeit beaten up a bit (parts of both ends are missing).

The same day, Ray was working on the jacket containing “Picasso’s” skull. Tim and Ray each found pieces that went together to make this:

Yet another Syllomus humerus! But we weren’t done; within a half hour Ray had pulled two more mid-shaft fragments of Syllomus humeri from the sediment around “Picasso’s” skull:

All of these bones were collected with “Picasso” in 2006, so they were actually found before the Syllomus humerus Drew and Amanda collected. We just didn’t know they were there until we opened the jackets and began preparing that material.

To confirm these identifications, we took the bones across the hall to the collections room to compare them to our other turtle remains. Now, it happens that our Carmel Church reptile material is housed in the same cabinet that holds our Carmel Church bony fish. While the case was open I happened to look in one of the fish drawers and found this:

Yet another Syllomus humerus, misidentified as a “unidentified fish bone” (it was in a tray that includes numerous bones that really are from fish). This was collected in 2000, so it was actually the first turtle humerus we found, as far as we know; there could be others lurking in the collection.

So as far as identifications are concerned, in the space of a hour last Thursday we went from having one Syllomus humerus to having six. In fact, we now even have a pretty nice ontogenetic series, with two large humeri, two medium-sized ones, and two small ones:

It’s interesting that four of these six bones were found with “Picasso”, over an area of about 3 square feet. Perhaps more interesting is that considering the comparative sizes and accounting for left and right sides, those four represent four different individuals. That makes me suspect that there are many more turtle bones in our unopened jackets.

Reference:
Weems, R. E., 1974. Middle Miocene sea turtles (SyllomusProcolpochelysPsephophorus) from the Calvert Formation. Journal of Paleontology 48:278-303.
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One Response to Fossil turtle soup

  1. George says:

    Butch

    This is a great find let me know if you need some volunteer work. I know over the years I placed shell and limb fragments in the SI collection, I have always been inerested in lower verts from the Calvert Group. All the best George

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