From the Collections Room (Proboscidean femur)

My friend Bobby Boessenecker (who blogs at The Coastal Paleontologist) published a paper today with Frank Perry in the journal Palaios (abstract). In the paper they describe circular bite marks found on several fur seal bones from the Miocene-Pliocene Purisima Formation in California. Circular bite marks are a bit unusual in marine mammals. Parallel linear bite marks caused by sharks are much more common, such as these massive cuts in a whale jaw from Peru:

Circular bites are much more common in terrestrial mammals. They’re essentially punctures caused by the canines (and occasionally premolars) of mammalian carnivores, which are circular in cross section. Sometimes the punctures go all the way through, and sometimes they cause a circular crushed area in the bone. A good example of this is on display at the University of Nebraska State Museum, where you can see a Moropus bone that was apparently bitten by the entelodont Dinohyus:

Compare the circular wound in Moropus to the fur seal radius figured in the paper:

Looking at the pictures in the Palaios paper, I was reminded of a partial proboscidean femur in the VMNH collection that we briefly placed on exhibit in 2009 (top of page). We don’t have a lot of information about this specimen; it came to the museum decades ago as a donation. I’m pretty sure it’s from the Pleistocene of Kentucky, and it’s most likely from a mastodon (Mammut americanum), although I haven’t yet ruled out a mammoth (Mammathus sp.). The image at the top of the page shows nothing remarkable in posterior view. But if we look at the anterior side, there’s a large circular depression that’s very similar to the ones in the fur seal and Moropus bones:

This is pretty clearly the same type of feature described by Boessenecker and Perry, even though its diameter is five times larger (note the scale bars). What could have caused such a puncture? Certainly the most obvious possibility is a large carnivore, particularly something like a bear as they are known to bite into bones. The giant short-faced bear, Arctodus simus (below, from Mammoth Site), is a Pleistocene species that has already been implicated in the scavenging of mammoth bones from Saltville, Virginia (Schubert and Wallace, 2009).

However, the location of this puncture on the anterior side of the femur does allow for another possibility. Research presented by Daniel Fisher at past SVP meetings indicates that, like modern elephants, mammoths and mastodonts engaged in male-male combat that resulted in horrific, and sometimes fatal, injuries from tusk stabs. That at least opens the possibility that the puncture in the VMNH femur was caused by the tusk of another mastodont.

This provides another point of similarity with the Palaios paper. Boessenecker and Perry suggest several equally likely candidates for inflicting the bites on the fur seal bones, including toothed whales, other pinniped species, and terrestrial carnivores. However, given that the bones are from a juvenile fur seal, they also mention the possibility that the injury could have resulted from a case of intraspecific infanticide, a behavior that is known in modern fur seals.

Congratulations to Bobby and Frank on the publication of this interesting and thought-provoking paper!

References:

Boessenecker, R. W. and F. A. Perry, 2011. Mammalian bite barks on juvenile fur seal bones from the late Neogene Purisima Formation of central California. Palaios 26:115-120. Abstract
Schubert, B. W. and S. C. Wallace, 2009. Late Pleistocene giant short -faced bears, mammoths, and large carcass scavenging in the Saltville Valley of Virginia, USA. Boreas 38:482-492.
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5 Responses to From the Collections Room (Proboscidean femur)

  1. Alton Dooley says:

    I’ve heard from several people that they’re having trouble posting comments.

    There seems to be a MobileMe glitch with comments that can be fixed (at least on Macs) by clearing your browser cache, then relaunching the browser. This works for Safari and Firefox, but I’m not sure about other browsers (I know a lot of websites have been having compatibility problems with IE7).

    Also, make sure the url is either “paleolab.org” or ” web.me.com…”. If you get to the site using the old ” web.mac.com…” url the page will load but comments won’t work.

    I’ll keep complaining to Apple to try and resolve the issue.

  2. Alton Dooley says:

    The following comment was emailed to me by Doug, who has been having trouble getting his comments to go through:

    “Very cool fossil. There is a mammoth skeleton from Utah that may have bear damage (don’t know for sure since the museum plaque didn’t specify. Also it said there evidence humans may have scavenged it as well). The femur does seem like an odd place for a tusk wound though. Especially given it’s orientation and the shape of mastodon tusks. Would make for an interesting exhibit though about the workings of paleontology.”

    I agree that the femur seems an odd place for a tusk injury, especially since (as far as I can recall) the injuries described by Fisher were to the skull. However, with other animals that fight with horns, antlers, and tusks, there’s no honor at all. Given the opportunity they’re more than happy to ram/stab their competitor in the side, rear, or whatever happens to be facing them. Given that, it’s easy to envision a scenario in which a mastodont could get stabbed in the back leg.

    That said, I wouldn’t say that I BELIEVE this was caused by a tusk, just that it’s possible. I think a bite from a carnivore is much more likely.

  3. Alton Dooley says:

    I’ve installed a software patch from Apple that’s supposed to address “issue with blog comments”. It didn’t specify with the “issues” are, but hopefully it will alleviate some of the commenting problems.

  4. Doug says:

    Exactly. It’s far less possible since it’s on the posterior portion (a tragic accident during a routine game of tag). Now if was on the anterior portion of a humerus, then i could see it as equally possible.

  5. Boesse says:

    Similar to the bite mark on the humerus we described, that’s kind of an awkward spot to get a puncture. I can’t remember if we addressed it in the version of the paper that got published, but I know that in an earlier draft we did discuss why there’s only a bite mark on one side of the humerus. We may have a shortened version of that in there… I can’t remember. In theory, occluding teeth should have left another a corresponding bite mark on the other side. That is of course, unless there’s a nice hunk of fur seal steak on the other side (and in the case of the humerus, the puncture occurs on the lateral side, which is closer to the skin of the shoulder region of a pinniped in life).

    It’s interesting that these are all on appendicular elements. I’m sure with a larger sample size from an assemblage like the White River Fm., you could do a pretty neat study mapping punctures and other bone modifications onto the skeleton. Otherwise – I think an even more awkward place for a puncture mark than a proximal humerus is the neck of an elephant femur – there’s quite a bit of elephant between that part of the bone and the outside of it’s thigh (or derriere, for that matter). I almost think that it would be easier to get a puncture there during/after dismemberment of the hindquarters of the animal.

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