Trace fossils on whale ribs

Piedmont Governor’s School student Zach Turman is doing a project on quantifying shark bite marks on the ribs of the Carmel Church baleen whale “Sinistra”. This whale was heavily scavenged by sharks, and he’s finding tons of bites. However, he also has been turning up other unusual marks that, so far, we haven’t been able to identify.

First are several small, circular depressions. These are vaguely similar to scars left on shells by the snail Crepidula, but these are much smaller and more perfectly circular. There are similar, but larger, marks on the sperm whale jaw we just finished preparing.

The second feature is a tiny, segmented linear feature that runs along the edge of one of the ribs. Here’s the whole structure (width of image ~ 1.5 cm):

And here I’ve zoomed in on the hooked left end:

This structure may be partly in the bone and partly in the sediment, although most of it appears to be in the bone. It is smaller than the points of any of the prep tools we use in our lab or in the field, so it’s not something we caused. It looks rather like the cross section of a spiral structure, so I’m wondering if it’s some type of spiral burrow.

At any rate, we’re still trying to figure out what these are, so if you have any ideas feel free to speculate in the comments.

This entry was posted in "Sinistra", Carmel Church mysticetes, Carmel Church Quarry, Chesapeake Group, Invertebrate Paleontology and tagged . Bookmark the permalink.

7 Responses to Trace fossils on whale ribs

  1. boesse says:

    Those are some very strange bone modifications! The linear one is very bizarre… I have no idea what could have caused that. There are definitely a lot of enigmatic marine bone modifications that no one has ever described.

    If the circular marks have a peripheral trench, they are probably barnacle scars. Actually, there’s a bit of variety in barnacle scars, and very few are known from vertebrate bones. For SVP this year I presented on some pleistocene sea lion bones which were encrusted with hundreds of barnacles, and several barnacles had fallen off, exposing the traces they made in the bone.

  2. Alton Dooley says:

    I’m not convinced that the circular marks are barnacle scars, although it’s not out of the question. I don’t think they look a lot like the barnacle scars I’ve seen on shells, and of course, at Carmel Church there are no preserved barnacles, not even as molds (no shells of any kind, except inarticulate brachiopods). I would thin if they were barnacles we would find molds of them in the sediment even if the carbonates are leached out. Also, I’d expect to see evidence for barnacle on some of the numerous rocks at Carmel Church, but so far there haven’t been any (at least not ones that I could recognize!).

    As for the linear structure, I’m clueless.

  3. boesse says:

    I wouldn’t discount it simply because there aren’t any shells or molds – barnacles have a nasty habit of falling off during transport. Additionally, given the rarity of calcareous shells at Carmel Church, that raises the possibility that it’s at least partially a chemical lag. If there were multiple phases of reworking, or if the bone sat out on the bonebed surface for a while prior to final entombment, that gives all sorts of opportunities for barnacles to be knocked off the bone surface.

  4. Alton Dooley says:

    All that said, at Raleigh today looking at the Balaenula skull I saw bunches of clear barnacle scars that look very much like these, so they do look very good for barnacles.

  5. boesse says:

    Cool! Are there any barnacles still attached to the Balaenula bones?

  6. Alton Dooley says:

    I think there are a couple of fragments. Dozens of scars, though, including some that grew next to each other and are subcircular as a result.

  7. Rob Gooden says:

    and the scrutiny goes on…and on..until you publish.!!(in school curriculae , I hope), eventually..!!

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