A bony toothed bird from the Purisima Formation, part 2

After I got the bone identified as a bird, I emailed pictures to my colleague N. Adam Smith, who at the time was a Ph.D. student at University of Texas at Austin, studying with Julia Clarke. We both agreed on the identification of the specimen as a pelagornithid, and also agreed that it could be written up quickly, and we immediately began working on the manuscript. This was the fastest paper I ever wrote - partially because each of us did about 50% of the work, and we went through a bazillion drafts (a new draft every 24-36 hours for four weeks in September and October), and we finally submitted it on Halloween.


We were pretty anal about properly figuring and labeling all the anatomic structures of this specimen in our paper; we were wholly dissatisfied with previous papers which had not labeled the relatively divergent anatomical structures of pelagornithid humeri sufficiently. Many anatomical features are fairly modified relative to non-pelagornithids, and without adequately labeled (or unlabeled) figures, it is difficult for the non-specialist to interpret their morphology; we thought we'd do everyone a favor and do it properly. One exception is Bourdon et al. (2010), who studied Eocene pelagornithids from Morocco (whose paper was also not out yet when we submitted our article).

Figure 2 from our paper, highlighting the anatomical structures of UCMP 219007.

A comparison of humeri of pelagornithids and modern pelecaniform and procellariiform birds. A- Pelagornis sp. (UCMP 219007); B- Pelagornis chilensis, late Miocene, Bahia Inglesa, Chile (holotype, from Mayr and Rubilar-Rogers 2010); C- Pelagornis miocaena, Miocene, France; D- Pelagornis sp., Pisco Formation, Peru (Pliocene); E- Morus bassanus, Gannet, extant (CAS specimen); F- Phoebastria irrorata, Waved Albatross, extant (CAS specimen); G - cf. Macrodontopteryx (synonymized with Dasornis iby Bourdon, 2010), Eocene, Belgium; H- Pelagornis mauretanicus, Pliocene, Morocco.

Many features of pelagornithids (and specifically, Pelagornis spp.) are highly divergent relative to other pelecaniformes (as you can see above, compared with Morus). Additionally, as you can see, our specimen is one of the most well preserved pelagornithid humeri now known, even more so than the beautiful holotype of Pelagornis chilensis, the humerus of which still has quite a bit of matrix encrusted and glued onto the bone, obscuring some of the fossae. One of the pneumatic fossae is actually pneumatized, and bears a pneumatic foramen that appears to connect to the internal cavity of the bone, a condition we had not read about or observed in any fossil or modern relative.

Shaded drawing I made and used for figure 3 of our paper, showing the pneumatic foramen.

Lastly, for our paper I thought I would try a skeletal reconstruction of Pelagornis. It was on my to-do list for the paper, and we already had a couple of drafts sent back and forth when Pelagornis chilensis graced the cover of JVP: it couldn't have been more timely. Although not in the original paper, associated with the press release were several skeletal reconstructions. I emailed the artist Carlos Anzures in Chile to ask for permission to modify it for our study. Well, I didn't just modify it; I redrew it by hand, reposed it, inked the drawing on vellum, and then edited the image in adobe illustrator, to eventually get something like what you see below:

Part of Figure 1 of our paper, showing the skeletal reconstruction of Pelagornis.

Next time: more on pelagornithid evolution and ecology, as well as biogeography and the implications of our find.

Bourdon, E., Amaghzaz, M., and Bouya, Baadi. 2010. Pseudotoothed birds (Aves, Odontopterygiformes) from the Early Tertiary of Morocco. American Museum Novitates 3704:1-71.

Mayr, G., and D. Rubilar-Rogers. 2010. Osteology of a new giant bonytoothed bird from the Miocene of Chile, with a revision of the taxonomy of Neogene Pelagornithidae. Journal of Vertebrate Paleontology 30:1313–1330.

Summer Adventures Part 7: Sea otter cranium with embedded shark tooth

On the friday of my last week of summer, I picked my girlfriend up from the SFO airport and we booked it to Golden Gate Park, where the prestigious California Academy of Sciences resides. Over the last five years their collections have been at their temporary facility near the Metreon. I visited several years ago (2007?) to look at northern fur seal skeletons. For my SVP presentation, I needed to compare my partial fossil Globicephala cranium with modern Globicephala, just to make sure my ID was correct. After I finished making my comparisons (and confirming my ID), I started photographing other marine mammal parts, and came across a box marked "Enhydra lutris nereis, with shark tooth!" E. L. nereis is the southern sea otter, which used to live from British Columbia south to Mexico; they were declared extinct, and have since repopulated, but only along Central California, and very slowly.
I pulled this skull out, and sure as s*** there was a tiny piece of a Carcharodon carcharias tooth embedded in the skull near the temporal/occipital contact or lambdoidal crest.
This skull was actually described and figured by Ames and Morejohn (1980), who described multiple cases of sea otter carcasses bearing tell tale bite marks in soft tissue, as well as two different bite morphologies: linear gouges, and parallel scrapes, originating from the serrations being dragged across the bone surface. They also figured about a dozen tooth fragments that had broken off and were embedded in soft tissue, and in some cases, skeletal tissue like this specimen.

Here's a closeup picture, and you can clearly see the serrations that diagnose Carcharodon carcharias.

Ames, J. A. and G. V. Morejohn. 1980, Evidence of white shark, Carcharodon carcharius, attacks on sea otters, Enhydra lutris: California Fish and Game, v. 66, p. 196-209.

Summer Adventures Part 1: Sea Lion Rescue

Aside from the random post about Chupacabras, I've been pretty silent the rest of the summer, for a few reasons. First and foremost, I was trying to catch up on thesis fieldwork, and also kept on finding some really great fossils (more on that later). I also went on a 5 day field trip with Dick Hilton of Sierra College to Plio-Pleistocene strata of southeastern Oregon and Northern California (part of my so-called North Coast Project). In addition to this, I also took a 5 day trip back up here to Montana for my girlfriend's older sister's wedding. Then, a week and a half at Lake Tahoe, and then more fieldwork. Oh, and a week long road trip back to Montana via Northern California and Oregon.

So, during my field work in the Santa Cruz region, I decided to head over to Pt. Santa Cruz and try out my new Canon EOS Rebel XS with a 300mm lens and photograph some of my favorite flippered friends: Zalophus californianus, the California Sea Lion. Now, last summer I spotted a couple Steller Sea Lion males (Eumetopias jubatus); it was obvious that they were Eumetopias and not Zalophus because of their lighter, hairier pelage, humongous size (nearly twice the size of obvious Zalophus males) and bearlike heads without a sagittal 'bump'.Zalophus yearlings at Point Santa Cruz, California

Anyway, I got a bunch of great photos of some of these guys. There were several dozen hauled out on the Point itselft as well as the rock offshore, mostly yearlings and the occasional subadult male, and a few pups (and lots of dead pups, in various states of decay; presumably starved to death). I saw a guy with a marine mammal center sweatshirt on, and I stroke up a conversation. Afterward, he asked me if I could help him capture a sea lion with an eye tumor. He pointed out the individual to me, and sure as hell, its left eye was in pretty bad shape.

Juvenile sea lion with eye infection.

So I naturally agreed, and he returned with a huge net and a dog crate built for a great dane. I was to bring the crate to him after he had netted the poor little guy; apparently the crate scares the sea lions away, and he suspects they may remember every time it appears, one of them gets abducted (yes, by aliens, just like in Happy Feet).

Marine mammal center 'Doug' capturing a juvenile sea lion with a very big net.

Well, let me tell you - I've had my fair share of vicious dog encounters, and I've seen big cats roar at the zoo, and seen pissed off bulls, and none of these were remotely as intimidating as this 80lb sea lion. This thing was biting at the net and shaking its head after it clamped down, all the while emitting the scariest growl/snarl I've heard from a vertebrate. Doug finally dragged it over to where I had placed the crate, and wrestled the sea lion into the opening. When it was nearly inside, a sea lion head with mouth agape and a beautiful set of (very sharp, unworn) homodont teeth with moderately developed lingual cingula and accessory cusps on the postcanines (yes, I had that much time to remark upon the dental morphology) found its way out of the crack between the net and the crate, and took a swipe at me, narrowly missing my hand by a couple of inches (I distinctly heard the teeth 'snap' just like when a dog shuts its mouth quickly).

The sea lion looks 'ok' from the right side...

...not so well from this side.

After we got 'her' in the crate, Doug informed me that California Sea Lions can easily bite through 1" thick plywood sheets with ease (and that their bites hurt like a *****). Based on canine size, it looked to be a 'she' - very skinny, narrow, canines are typical of otariid females. Doug informed me that Northern Fur Seals (Callorhinus ursinus, my favorite pinniped) are by far more aggressive and ferocious than any sea lion. This news warmed my heart, as Callorhinus actually has a pre-Pleistocene fossil record (and if you include its ancestor, Thalassoleon, the Callorhinus-Thalassoleon lineage is the best preserved otariid lineage in the fossil record).

The eye injury, according to Doug, was most likely an infection, as tumors are more typical of old adults. In this case, the eye had gotten infected, and the lids had more or less rotted away (very technical, I know), leaving the actual eye to prolapse (it was actually hanging out of the orbit a little bit). I can only assume that the marine mammal center will amputate the eye, and cauterize the orbit shut.

The female sea lion just before removing the crate from the Point.

In any event, a look at the last photo shows something interesting: this individual was pretty plump, and showed no signs of emaciation (most of the other yearlings looked pretty starved), and was slightly larger than the other yearlings in the vicinity. This eye infection was obviously more than a few days old, but it apparently didn't affect her ability to survive and forage. So, a happy ending - she will most likely survive to raise many pups.

Field Camp, Part 2: Yellowstone NP

The igneous geology portion of field camp naturally brought us to Yellowstone National Park, one of the largest 'supervolcanoes' on earth. Yellowstone is a bimodal volcanic center, and erupts both felsic (Feldspar/Silica rich) Rhyolitic lava and mafic (Magnesium/Iron rich) Basaltic lava. Yellowstone National Park is situated within several nested calderas; each of these calderas formed after an eruption. The shallow (5km deep) magma chamber lost so much magma during each eruption that the earth's crust above the chamber collapses into the void. The caldera has since been filled with lava flows. The fractures and faults within the caldera allows for the incredible hydrothermal features within the park to occur.

Professor Colin Shaw explaining the classification scheme for igneous rocks using the infamous tertiary diagram.

Upper Yellowstone Falls.

Fountain Paint Pots, easily my favorite feature in the entire park.

Another paint pot.

Old Faithful Geyser, in the Upper Geyser Basin.

Lecturing at the Duck Lake overlook, the site of a huge hydrothermal explosion. Duck Lake is the explosion crater, and has a ring shaped hill around it, which is the ejecta blanket.

Mud volcano! Similar to the paint pots in several regards. The mud cinder cone here used to be over 40' high if I remember correctly.