Thursday, January 26, 2012

Southern California Research Trip, Part 3: Natural History Museum of Los Angeles County (collections)

The purpose for our trip to visit the LACM collections was to examine a large collection of pinniped fossils housed there. Curator Emeritus Dr. "Larry" Barnes has been studying fossil pinnipeds since his master's thesis in the late 1960's (which he published in 1972, on Allodesmus and other desmatophocid pinnipeds), and has researched a wide variety of fossil pinnipeds including the early diverging and 'primitive' enaliarctines (a paraphyletic group of early pinnipeds), the relatively large and aberrant desmatophocids (an extinct group of phocoids known only from the North Pacific), all manners of fossil walruses, and fossil sea lions and fur seals. Larry has named quite a few fossil pinniped taxa from the northeastern Pacific region (Enaliarctos mitchelli, Pteronarctos goedertae, Pteronarctos piersoni, Pacificotaria hadromma, Desmatophoca brachycephala, Allodesmus gracilis, Proneotherium repenningi, Pelagiarctos thomasi, Gomphotaria pugnax, and Proterozetes ulysses), and there are a whole slew of holotype specimens to look at at the LACM - including a number of other important finds, including crania and jaws of the walrus Imagotaria downsi and the even earlier Neotherium mirum (but not quite as old as Proneotherium...). Our goal was to photograph all of these skulls and jaws, and take all sorts of measurements of them for our research. Between Morgan and I, we took about 5 gigabytes of photographs of these fossils. At the moment, we have two concurrent research projects which will soon be culminating in submittable manuscripts: a phylogenetic analysis of fossil and modern sea lions and fur seals (Otariidae; Morgan gave a talk on this at SVP this last fall), and another project describing some new material of the extinct "killer" walrus Pelagiarctos, originally described by Larry Barnes from the Sharktooth Hill Bonebed, and discovered by LACM head preparator and all around fun guy Howell Thomas. At bare minimum, we needed to examine, photograph, and measure the holotype "chin" and the referred teeth. Anything else we got done was a bonus - and our bonus included looking at dozens and dozens of skulls, jaws, and teeth of various other pinnipeds.

The hollywood hills can be seen very well from the prep lab, which is several floors up. You can just make out the hollywood sign below the top of the mountains.

The holotype "chin" of Pelagiarctos thomasi.

A referred lower left third or fourth premolar of Pelagiarctos, published by Barnes (1988).

My wife borrowed some of the clay we used for propping oddly shaped specimens up during photography and made a walrus and a manatee; the manatee even has
motorboat propeller scars (just for J. Velez-Juarbe!)

A referred lower jaw of Neotherium mirum from the Sharktooth Hill Bonebed, published by Barnes (1988); this is the only other early walrus from the middle Miocene bonebed.

My wife happened to find a book of 3D cat photos with 3D glasses. Don't ask.

Three different jaws of Allodesmus from the Round Mountain silt; but how many species? According to Barnes, there are three species: the topmost is the holotype of Allodesmus kelloggi, the middle is the holotype of Allodesmus kernensis, and the bottom one is Allodesmus gracilis. Others would lump all these in to Allodesmus kernensis (which would have taxonomic priority).

Three different early walruses! From left to right, they are Proneotherium repenningi from the Astoria Formation of Oregon (early Middle Miocene), Neotherium mirum from the Sharktooth Hill Bonebed of California (late Middle Miocene), and Imagotaria downsi from the Santa Margarita Sandstone (early Late Miocene) of Santa Cruz County, California.

The beautifully preserved holotype skull of Pacificotaria hadromma from the Astoria Formation of Oregon. According to Berta (1994), this may be a junior synonym of Pteronarctos.

Morgan and I conducting research amid a chaotic mess of fossil pinnipeds and other paleontological debris.

Downtown Los Angeles from the window in the prep lab. The US Bank tower can be seen in the middle. If you recall, it was blown to smithereens in Independence Day.

The rostrum and upper dentition of a referred snout of Desmatophoca oregonensis.

Morgan photographing the obscenely gigantic jaw of the bizarre double tusked behemoth of a walrus Gomphotaria pugnax. Seriously, that thing is offensively large.

The holotype skull of Allodesmus kelloggi, described by Ed Mitchell in the mid 1960's from the Sharktooth Hill Bonebed.

An undescribed late Pleistocene jaw of a California sea lion, Zalophus sp., from the Newport Bay mesa.

Last, but not least, another shot of those three walruses -
Proneotherium, Neotherium, and Imagotaria.

What's up next? One or two more posts on the southern CA trip including the Page Museum as well as the Santa Barbara Museum of Natural History, and eventually, I should probably try and cover some recent marine mammal research, I still have to cover a paper I got published on our wedding day, Kolponomos, and a bazillion other things.


Doug said...

Again, how i envy you...

Really, Santa Barbara Museum? I'm guessing that's more for modern marine mammal material? I'd meet up with you down there, but you probably don't have the time.

And who knows, maybe 20 years down the road you'll be stopping at my museum to check some stuff out...

J. Velez-Juarbe said...

Propeller scars, very proper hehehe!!

Those Allodesmus mandibles, how distinctive are they, really, I'm skeptical. Can it be that A. kellogi is a female, hence the smaller size, and the other two represent males of the same species?

And what's with the blurred fossil in the pic of you and Morgan? Is it something Mitchell is working on and you were told not to show it in case he sees it... or is it a baculum and you're trying to keep this blog PG-rated Hahaha

Robert Boessenecker said...

Doug: We weren't research visitors. We stopped in so I could photograph the weird sperm whale, and the Pelagornis orri holotype.

Jorge - I'll admit I'm fairly skeptical as well. I am puzzled by many of the taxonomic decisions by Barnes and Hirota 1995, and that is one of them. I think I'm going to do a series of post on desmatophocid taxonomy; I'm also going to do a long series of posts on various fossil pinnipeds, something like "Better know a fossil pinniped, part 47: Valenictus", a la Stephen Colbert.

The blurred specimen is an unpublished Allodesmus gracilis from Sharktooth Hill; Larry didn't want us to publish any photos of it, and in fact, I offered not to take an photos at all, but it made its way into this single image - so I blurred it out. I would never blur out a baculum!

Doug said...

ah, got it. I emailed Alton Dooley pictures of that skull and he thinks it's Zygophyseter. The cranium is restored, erroneously according to Alton.

Robert Boessenecker said...

To be quite honest, that was the thing that struck me when I saw it in person - it's a good thing I came to the same identification independently! But alas, that's a topic for another future post...

Chuck Powell said...

Regarding the undescribed late Pleistocene jaw of a California sea lion, Zalophus sp., from the Newport Bay mesa. Its been many, many years but I think that specimen was collected by Jim Harroll ( I think that was his name) in the 1970's from a trench across the top of the mesa. Jim is now a professor of geology at a university back east. If you want more information let me know - I still remember him collecting that specimens (or it could have been another, but it looked very similar).