Barnacle scars revisited

A few weeks ago I posted about circular trace fossils on the ribs of “Sinistra”, the Carmel Church Diorocetus. In the comments on that post, boesse and I debated whether or not these were barnacle scars, and I was eventually convinced that they were after seeing similar features on the Lake Waccamaw Balaenula skull. After boesse commented that barnacle scars are quite rare on vertebrate bones, I began wondering if we might have other examples in our collections. It took me just a few minutes to find an example.

The two fragments shown here are pieces of the maxilla (upper jaw) of a baleen whale, probably from the same individual. They were collected on the James River in Surry County, Virginia from the Lower Pliocene Sunken Meadow Member of the Yorktown Formation.

Between the two pieces there are at least 26 circular or near-circular markings. No barnacle fragments are preserved, but it’s noteworthy that all the scars occur on the ventral (bottom) surfaces of the bone. This is the side that would have been exposed if the skull landed in the typical ventral-up position that is seen so commonly in fossil whales.

Of course, what’s most exciting is that this gives me an opportunity to re-post one of my favorite home videos, footage of actively feeding barnacles that Brett shot at Acadia National Park (although they’re not attached to whale bones):

Tomorrow I’m spending the day at a student conference at Roanoke College, and I’ll be posting on the paleo-related talks presented there, but next week I’ll be posting a little more about barnacles and whales.

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This entry was posted in Chesapeake Group, Invertebrate Paleontology, Modern critters and tagged . Bookmark the permalink.

4 Responses to Barnacle scars revisited

  1. boesse says:

    Those are beautiful scars! Are they actually excavated, or are they just stains? Depending upon the type of barnacle, the scar morphology can be quite different.

  2. Alton Dooley says:

    At least some of them are slightly excavated, but a few appear to be stains. I don’t have the specimens in front of me at the moment.

  3. Aydin says:

    It has been claimed that some limpets home, that is, return to the same spots after foraging. Therefore, they too may create scars, although I don’t know how visible those would be.

  4. Alton Dooley says:

    I remember as an undergrad seeing limpets on rocky coasts in Bermuda that were hunkered down into pits in the rocks at low tide. I remember thinking they had made the pits, but I don’t recall if someone told me that or if I assumed it. Most limpets are oval rather than circular, so that might be detectable.

    Crepidula (slipper shells) will leave deep oval scars on pecten and oyster shells. Many specimens of Chesapecten in the late Miocene-Pliocene have these scars.

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