Monday, October 5, 2009

Summer Adventures Part 5: new Herpetocetus cranium

Hey gang, I've finally returned from SVP and London, and finally beaten (nearly) this bad cold I've had (several of my office mates keep insinuating that I got swine flu; some other MSU students did - I was not so unlucky). So, in keeping with the attitude of my most recent posts, I will continue on with my summer adventures.

Earlier this summer I made a quiz type post, and never bothered following up on it (except in the comments). Well... for those of you too lazy to figure out what it was, now I'll show you.
I've shown the dorsal surface of the unprepared fossil adjacent to a photo of the well preserved cranium of Herpetocetus bramblei that I presented on at SVP in 200, with certain features lettered. A=zygomatic process of the squamosal; B= vertex; C = occipital condyles; D = exoccipital 'crest'. Herpetocetus, while exhibiting some decidedly 'primitive' features (primitive isn't politically correct, but given the nature of the cetacean cranium, its really convenient, and since this isn't peer reviewed, I don't care about 'PC'), also has a radically telescoped cranium. The radical telescoping isn't very obvious from the posterior cranium, though, and instead the primitive features are more salient. These include the extremely narrow and triangular supraoccipital shield, and the very anteriorly oriented zygomatic processes. Not terribly obvious from this specimen (because they are worn off), but very obvious on the H. bramblei cranium I have are vertically oriented, very well developed lambdoidal crests; these are typically laterally oriented in mysticetes, overhanging the temporal fossa. Now I'm just yapping; maybe I should really focus my chi into writing up that description...

In any event, the new fossil as exposed shows several diagnostic features of Herpetocetus (outlined above[ish]), and some features (such as the narrow supraoccipital) that are unique as far as Pliocene (and latest Miocene) mysticetes go. This last photo shows the slab (very, ver, very) slowly dissolving away in an acetic acid bath. I let it go while I was gone at SVP... and it didn't look any different when I got back. Acetic acid doesn't really degrade Purisima Formation nodules; it pretty much just softens them up to make airchisel prepping easier.

Stay tuned, folks - I still have tales to tell of fieldwork with Dick Hilton in Oregon, shark teeth lodged in sea otter skulls, and some other less interesting stuff I can't seem to remember at the moment.

Oh, and I got to be the 6,000th visitor to this blog - I rule.


J. Velez-Juarbe said...

Hi Robert,

You've got some pretty cool material there. The well preserved skull of Herpetocetus bramblei looks so much more complete than the holotype. Actually, looking at Whitmore & Barnes (2008), your H. bramblei looks more complete than the other species of Herpetocetus! Are you going to write it up?

That Purisima nodule looks hard, reminds me of all those unprepared block collected by Emlong. Good luck with the prep work!

BTW, I'll be in Oregon in a week or so, any recommendations?

Robert Boessenecker said...

The H. bramblei and H. transatlanticus holotypes are pretty incomplete, but they still retain oodles of synapomorphies. Neither holotype has a preserved vertex. There are two additional undescribed species - one from the Pliocene of Japan, and another from the Pliocene San Diego Formation.

The new cranium of H. bramblei that Jonathan Geisler and I presented on last year is much more complete and better preserved than the Japanese specimen, and is about as complete as the San Diego specimen, but unfortunately the San Diego cranium is highly crushed and was prepared very poorly, and is undergoing re-preparation currently at the SDNHM, thanks to Tom Demere.

Jonathan and I will be writing up the Herpetocetus material... *soon* - unfortunately, Herpetocetus isn't exactly 'rare' in the Purisima, and now there are about 6 or 7 referred petrosals, several dentaries of varying completeness, a humerus, and now this second cranium (there are two more crania still in the field waiting to be collected - one in soft sandstone, another in a gigantic concretion).

Oregon... I don't want to give away anything about my 'secret' locality, so I'll email you about that; otherwise, the Empire Formation near Coos Bay (=Fossil Point) is the type locality for the monstrous "killer walrus" Pontolis magnus, and then there are Yaquina and Astoria Fm. outcrops closer to Lincoln City and Newport, OR. I'll email you later today about it.