Thursday, June 4, 2009

Preservation biases of fossil cetaceans

I have been quietly writing a series of posts for this blog, lengthy and full of figures, and now that I am close to posting some of them, I came across something short and sweet that I cannot resist posting about. So, I guess the longer posts will have to wait.

This morning, when I read the newest MarMamm listserv posts, I came across a new paper on minke whale habitat preferences off the coast of Scotland. Several years ago I would never have read that paper, mainly out of a lack of interest in focusing on baleen whales. Since then I have had the pleasure of working more closely with Alton "Butch" Dooley of the VMNH (see his blog). Butch has been finding numerous, well-preserved, mysticete skulls and skeletons in the Miocene age rocks of Carmel Church Quarry in Virginia. These animals are quite a puzzle at times, mainly because of their size they are rarely so well preserved, and the logistics of collecting them has deterred many in the past and resulted in specimens that a few and far between. Anyone working on dinosaurs may know how it feels, but suffice it to say that if you are interested in really understanding fossil species, preservation and sample sizes matter. As a paleobiologist, what Butch is collecting in VA is an ideal and rare opportunity.

Ok, back to the paper of the morning. Kevin Robinson and colleagues in Scotland and Wales very recently published a paper on the habitat preferences of modern minke whales in the journal, Journal of Coastal Conservation. In it, they present a consistent link between the distribution of minke whales (Balaenoptera acutorostrata) and habitat details, such as seafloor physiography and sediment type.

I know this is a stretch, but I cannot help but think that this close connection of some, but perhaps not all, mysticetes to a habitat type might be useful in explaining the distribution and preservation of large fossil cetaceans. I don't mean to push it too far, but this could serve a role similar to the way terrestrial paleo folks regard the lack of montane taxa preserved (or at least, they all should). I know it is logical, but it is nice to find modern support for the idea that the record of fossil mysticetes may be biased to those that prefer habitats that preserve well.

This may also be a point of curiosity regarding how/why we get physeterid fossils, even though physeterids are supposedly more pelagic. I don't mean that fossil physeterids were not pelagic, but it is worth considering all the possible influences on distribution of fossil cetaceans, and maybe use taphonomy to better understand what animals are part of a local fauna, and which are bodies washing into it from afar.

These are all things to think about, although perhaps nearly impossible to approach as a study due to the complications involved in confirming this sort of data widely for modern mysticetes, and even more difficult for attempting to link studies of physiography and sediment types with meticulously collected fossil mysticetes. But, I hope it is an entertaining thought for the day and look forward to any comments you all might have.


  1. Interesting study. I looks like the strong correlation with sediment type is not because that sediment is associated with a particular depth (as I had suspected). Rather, they suggest that the particular sediment type provides a habitat for a minke prey item (sandeel).

    That suggests that different mysticete taxa would correlate with different substrates, assuming they are feeding on different prey. I think I see a follow-up study in the future...

    Thanks for the plug for my blog; I've added a link to "The Aquatic Amniote" to my page.

  2. This is a hypothesis I've built into my master's thesis to test (generally speaking, facies level control on preservation of marine vertebrates across a paleoshelf).

    The result certainly will be interesting; I'm predicting (based on previous observations of the Purisima Fm) that nearly zero ecological information (i.e. corrrelation between mysticete fossil occurrences and original habitat preference) survives on siliciclastic shelves. The problem of course is that 95% of mysticete fossils in the Purisima are balaenopterids, which haven't really been worked on, and I'm not entirely certain how many taxa exist. Certainly there is one undescribed genus with a distinctive skull, but due to local logistics and the size of these things, we have parts and pieces with a very low N. Thus, due in part to its size, and my familiarity with it, at present Herpetocetus is one of the only easily distinctive mysticetes... otherwise, balaenopterids and balaenids can only be treated at the family level.

    I certainly need to find more petrosals...