Coming soon: Oregon coast road trip with Kirk Johnson and Ray Troll

Later today, my wife and I will depart on a four day road trip along the Oregon coastline. We were invited several months ago for this trip by the dynamic duo, shortly after meeting them in person back in October. Kirk and Ray are putting together a new book as a sequel to Cruisin' the Fossil Freeway. The new book project is titled "Cruisin' the Eternal Coastline: the best of the fossil west from Baja to Barrow". The new book will cover all sorts of paleontological sites along the west coast, including Alaskan dinosaurs, the La Brea tar pits, Californian marine reptiles, the John Day fossil beds, and due in part to the coastal focus of their new project – the extremely rich and diverse marine mammal assemblage from the west coast.Kirk Johnson and I checking out a slab of the Concretionary Bed of the Purisima Formation near Santa Cruz, California. Photo courtesy Ray Troll.

An articulated baleen whale vertebral column sits in a multiton block in the foreground, with Kirk and I looking for smaller fossils in the distance. Photo courtesy Ray Troll.

Here I've spotted a baleen whale skull to show Kirk - I first spotted this specimen in 2002, and it's still there. It's in a 400 lb block, so it is likely not going to go anywhere for a while unless some heavy machinery is involved. Photo courtesy Ray Troll.

One of the most notable series of fossil localities are exposures of various strata in the Newport Embayment (a geological basin), including the Alsea Formation, Yaquina Formation, Nye Mudstone, and Astoria Formation. The eccentric, extraordinarily gifted, and tragic figure Douglas R. Emlong amassed an incredible collection of marine mammal fossils from this area and elsewhere in the Pacific Northwest during the 1960's and 1970's, prior to his premature death in 1980. One of the purposes of our trip is to visit several of Emlong's famed fossil localities as a pilgrimage of sorts, and pay homage to the great collector.

Douglas R. Emlong, with the partially prepared skull of USNM 215068, a male skull of the early walrus Proneotherium repenningi. Presumably this is during preparation in the Paleobiology Department at the Smithsonian Institution, during one of his visits to the east coast museum. From "The Ore Bin".

Previously, in October, I met up with Ray and Kirk when they were in California for a week. We took a day trip down to Santa Cruz where I showed them some fossil localities, and all in all had a rather nice day – although I didn't find a damn thing (thanks to there being little erosion over the prior 20 months). As it turns out, Ray and Kirk have increasingly been picking my brain for details on fossil marine mammals from the eastern North Pacific, and I am pleased and excited to help them with their project; most popular books on paleontology deal with dinosaurs, and very few have ever really touched the subject of marine mammals (Neptune's Ark by David Rains Wallace is an exception). Needless to say, I am very excited for their project to take off.

I found out that if the first fossil locality you go to is kind of ugly and has few fossils (but used to have a lot...), Ray Troll will make you pose with the crappiest fossil you find and a bunch of garbage he finds laying about. Included is a toothbrush, a cardboard mayan calendar, a random photo album (yes, we looked through it) and some other odds and ends; I'm pointing to a rather unassuming scrap of sea cow (Dusisiren jordani) bone. True story.

Fossil Fur seals from Northern California, part 2: The Gilmore Fur Seal

In 1948, Gretchen Burleson published a short article on some fossil pinniped jaws discovered in the Pliocene San Diego Formation, a sandstone mollusk-bearing unit that forms the hills of the San Diego area. These were some of the earliest pinniped fossils to be described from California - previously only a handful had been described, including the strange phocoid Allodesmus from the Sharktooth Hill Bonebed near Bakersfield, California, the woefully incomplete walrus (then assumed to be an otariid) Pliopedia pacifica from the Kettleman Hills, the hopelessly squashed fur seal Pithanotaria from Santa Barbara, and the even stranger Dusignathus santacruzensis from Santa Cruz.

All of these creatures were assumed then to belong to sea lions: most of them were large, and relatively robust, and differed markedly in many respects from true seals. Most of the early descriptions of pinnipeds we now know to be walruses are seemingly obsessed with comparing them to sea lions, and no doubt early workers such as Kellogg were frustrated with the alien nature of many of the fossils: they were about the same size as sea lions, but there were just so many little differences. The answer would not come until much later when decidedly modern researchers like Charles Repenning realized the true walrus affinities of many of these critters (like Pliopedia and Dusignathus).

Unlike the rather large and aberrant jaws of Allodesmus kernensis and Dusignathus santacruzensis, the fossil jaws from San Diego looked like a perfect match for a modern sea lion or fur seal: it had a shallow jaw with small triangular cuspate teeth, and the jaw was rectangular (i.e. the dorsal and ventral margins are parallel). The larger jaws of other better known pinnipeds had too many specialized features to be ancestral to sea lions: Dusignathus had widely flaring jaws without incisors and a canine that projected anteriorly, while Allodesmus lacked cusps on its postcanine teeth, which looked instead like little onions or bulbs. Burleson (1948) assigned these specimens to Pithanotaria, despite the much older age of Pithanotaria starri material described by Kellogg (1922) and the lack of actual morphological characters that identified the jaw of Pithanotaria. Burleson (1948) thought this specimen had a morphology intermediate between Pithanotaria and the modern Northern Fur Seal, Callorhinus.

Skull and dentition of a modern female Callorhinus ursinus, showing

single rooted, cuspate teeth.

In a much later paper by the preeminent paleo-pinnipedologist Charles Repenning and carnivoran researcher Richard Tedford (1977), this specimen was briefly discussed and they concluded that it did not represent Pithanotaria and was likely much closer to Callorhinus ursinus. After observing trends within the dental evolution of walruses like Imagotaria, Repenning and Tedford (1977) had identified the utility of the stage of root fusion as a taxonomic guide. For example, all modern otariids (fur seals and sea lions), the walrus, and some seals have single rooted teeth, while primitive pinnipeds and terrestrial carnivorans retain a number of double and triple-rooted teeth. For whatever reason, these root lobes coalesced through time and resulted in single rooted teeth in a number of taxa.

The dentary of the holotype of Callorhinus gilmorei, from Berta and Demere 1986.

Repenning and Tedford (1977) were surprised that Burleson (1948) had not noticed the interesting configuration of the tooth roots of this specimen: the third and fourth premolars and the molar were still double rooted, while only the first and second premolars were single rooted; in the modern Northern Fur Seal, Callorhinus ursinus, all the lower premolars and molar are single rooted. It was indeed a fur seal, but retained some interesting primitive features.

In 1986, after an extensive excavation of a bonebed in the San Diego Formation that would be christened the Mission Hills Bonebed, additional remains of this fossil pinniped were discovered including several jaws, teeth, skull fragments, and postcranial bones. The discovery of a partial skeleton of an immature female skeleton allowed Annalisa Berta (San Diego State University) and Tom Demere (San Diego Natural History Museum) to describe the San Diego fur seal as a new species - and sure enough, they found that its features placed it as a close relative of the modern Northern Fur Seal, Callorhinus. They named it Callorhinus gilmorei, named after Dr. Raymond Gilmore. In other regards, Callorhinus gilmorei was a relatively small fur seal - substantially smaller than modern skeletal remains, with less strongly developed cusps on postcanine teeth, and a more 'primitive' state of root fusion.

The new specimen of Callorhinus gilmorei from the Rio Dell Formation of Northern California described by Boessenecker (2011)

Subsequently, Kohno and Yanagisawa (1997) reported a tiny partial jaw from the late Pliocene of Japan. This jaw exhibited double rooted cheek teeth (although the anterior premolars were not preserved), and had accessory cusps on the cheek teeth, so they identified it as Callorhinus gilmorei. This extended the range of the Gilmore fur seal to the western Pacific - similar to the range of the modern Callorhinus ursinus.

Needless to say, I had a few ideas to follow once I started looking into Bushell's fur seal specimen. Fossils of C. gilmorei had so far only been found in Middle to Late Pliocene deposits, whereas in the late Miocene and earliest Pliocene of Japan, California, and Mexico the earlier fur seal Thalassoleon occurred (which has all double rooted teeth, and lacks cuspate cheek teeth, among other differences). The new specimen only has one cheek tooth - but it has a well developed accessory cusp, like C. gilmorei, and the first two premolars are both single rooted - also like C. gilmorei. In addition, it is relatively small - many other modern otariids are substantially larger. Furthermore, C. gilmorei appears to be the only middle-late Pliocene otariid in the entire Northeastern Pacific fossil record, which made the identification process somewhat easier.

Next up: Other fossil otariids from California and Oregon, and the Pleistocene Callorhinus
specimen.

References:

Berta, A., and T. A. Demere. 1986. Callorhinus gilmorei n. sp., (Carnivora: Otariidae) from the San Diego Formation (Blancan) and its implications for otariid phylogeny. Transactions of the San Diego Society of Natural History 21:111–126.

Boessenecker, R.W. 2011. New records of the fur seal Callorhinus (Carnivora: Otariidae) from the Plio-Pleistocene Rio Dell Formation of Northern California and comments on otariid dental evolution. Journal of Vertebrate Paleontology 31:2:454-467.

Burleson, G. L. 1948. A Pliocene pinniped from the San Diego Formation of southern California. University of California Publications in Zoology 47:247-254.

Kellogg, R. 1922. Pinnipeds from Miocene and Pleistocene deposits of California. University of California Publications, Bulletin of the Department of Geological Sciences 13:23–123.

Kohno, N., and Y. Yanagisawa. 1997. The first record of the Pliocene Gilmore fur seal in the Western North Pacific Ocean. Bulletin of the National Science Museum, Tokyo 23:119–130.

Repenning, C. A., and R. H. Tedford. 1977. Otarioid seals of the Neogene. US Geological Survey Professional Paper 992:1–87.

Fossil Fur seals from Northern California, part 1: discovery

Earlier this week saw the publication of my third article, concerning fossil fur seals of the genus Callorhinus from the Pliocene and Pleistocene of Humboldt County in Northern California. This paper has been in the works since 2006; I presented a poster on this topic at SVP in 2007. I did some of the initial research in 2006 and 2007, and after my SVP poster, I tried a couple more drafts of the manuscript - but it, along with a couple of other projects, fell by the wayside until I started graduate school. It wasn't until I had the herpetocetine jaw paper off my plate that I returned to this project, and in may of last year I submitted my completed MS to the Journal of Vertebrate Paleontology after three years of intermittent research.

The first page of Boessenecker (2011)

The story really starts in 2004. My buddy Ron Bushell, who helped me identify many of my fossils when I was still in High School, was collecting at a fossil site in Humboldt County, California. At this particular locality, he was looking for large concretions from the Rio Dell Formation which occasionally bear beautiful scallops (Patinopecten) the size of dinner plates, and incredible 6-10" long gastropods.

Ron and his collecting partners walked down the riverbank looking for nodules bearing mollusks, and thought he had hit the jackpot when he found a large nodule, about 2 feet in diameter, just sitting there in the gravel bar. Now, Ron is an experienced nodule collector - he's spent a lot of time collecting nodules with mollusks from the Pliocene and Pleistocene of Humboldt County, and Eocene crabs from Oregon and Washington.

So, if you're a nodule collector, naturally you take out a sledge hammer and attempt to destroy the concretion. Many concretions have nothing in them, and it is better to crack them in the field rather than lug them home and find out later (at some crab localities, Ron knows well enough which concretions will have crabs, and which ones won't, and packs them all out, and cracks them in his garage). Well, he broke this concretion open, and instead of white shells being exposed, familiar (but much rarer) brown fragments flew out onto the river bank - he immediately knew that he had found bone.

Initial preparation of the Bushell specimen.

Normally, Ron would keep any vertebrate fossils from this locality, due to their rarity. However, he also noticed a tooth fragment - and he knew he had found something pretty important. So, just like any crab or mollusk fossil, he collected all the pieces, took them home, and glued them all together in his garage, and begun airscribing the fossil.

Continued preparation of the Bushell specimen.

As it turned out, Ron had found two associated lower jaws (left and right) of a small fur seal, preserved beautifully in relief in a large concretion. He posted these photos on the old "Collecting fossils in California" forum, and I was very interested once I saw it. After a few emails, he offered to let me study the specimen - an opportunity I was most excited for.

Finished preparation of the Bushell specimen.

The Bushell specimen as it was when I first saw it.

The following summer, my fiancee (then girlfriend) and I drove out to California for the summer, but took a detour through Oregon and Humboldt County in order to visit Ron and pick up this beautiful specimen. Thanks to Ron's generosity, this fossil was made available to study - and now (finally, five years later) Ron's wish that it be studied finally culminated in my paper in the Journal of Vertebrate Paleontology.

Next up - introduction to the "Gilmore Fur Seal", Callorhinus gilmorei.

Boessenecker, R.W. 2011. New records of the fur seal Callorhinus (Carnivora: Otariidae) from the Plio-Pleistocene Rio Dell Formation of Northern California and comments on otariid dental evolution. Journal of Vertebrate Paleontology 31:2:454-467