The Wide World of Vertebrate Paleontology (Local Edition): Summer 2015

The desmostylian Behemotops (illustration by Carl Buell)
Beatty & Cockburn 2015

Fall has fallen and I'm enjoying the sensation of being able to enjoy autumn without the prospect of months of soul-sappingly cold weather on the horizon.  To mark the turning of the seasons and to continue my ongoing celebration of being back in the Northwest, let's take a look back at some of the paleontological headlines from this part of the world back when days were longer and temperatures were higher.

• "Suciasaurus": The story that made the most headlines this summer was the description of a new dinosaur from Sucia Island, the first ever found in Washington.  The specimen consists of part of a femur, which is sufficient to identify it as a theropod, the group that includes all carnivorous dinosaurs and birds.  Beyond this, it's hard to say for certain precisely which type of dinosaur it represents, but the size and age of the specimen make a tyrannosaurid the most likely candidate.  While the specimen was found in the San Juan Islands and described by UW paleontologists, the animal itself probably lived and died much further south, ferried north by tectonic activity.  Exactly how far south?  That depends on your interpretation of the complex tectonic history of the West Coast - likely somewhere equivalent to either Alta or Baja California.
• Zoneait: A much more impressive specimen of a Mesozoic archosaur was described by Iowa paleontologist Eric Wilberg.  The specimen in question is from central Oregon and is the remains of a thalattosuchian - a seagoing crocodile from the Jurassic.  It's an especially early member of the group, and its age and combination of traits suggest that the evolution of this group of crocodilians was mosaic in nature: adaptations to a marine lifestyle evolved piecemeal rather than all at once.
• New fossils of Carnivores, Primates, and Desmostylians: Archosaurs are great and all, but the strength of the Northwest vertebrate fossil record is mammal remains, and this summer saw the description of new material for several species.  Some are close relatives of living taxa, such as the ringtail Bassariscus, described for the first time from the Pliocene Ringold Formation by Eric Gustafson.  Others are long-time favorites of mine.  Ekgmowechashala is unusual for so many reasons.  It has a tongue-twisting Lakota name (meaning "Little Cat Man," as the Sioux had no word for monkey). It was the last primate in North America until the arrival of humans around 15 thousand years ago.  Its nearest relatives - and indeed all other primates - disappear from the North American fossil record a good six million years before it appears in the Oligocene of South Dakota and Oregon, begging the question of whether it survived in patches of forest or migrated from Asia.  New material from the John Day Formation, described by a team led by Josh Samuels, muddies the water even further, suggesting that Ekgmowechashala belonged to a primate group known as adapiforms, not to the omomyids, the group to which it had previously been assigned.  Probably the weirdest of the taxa for which new material was described this summer was the desmostylian Behemotops.  Desmostylians were (probably) afrotheres, relatives of elephants and sea cows, that were marine and evolved the thickest tooth enamel of any mammal.  While Behemotops is not a new genus, the new material from Vancouver Island described by Brian Beatty and Thomas Cockburn sheds light on that genus' morphology and on the evolution of desmostylians as a whole.  It also allows the reidentification of existing material from Seal Rock, Oregon as a new genus.  As with many of the taxa discussed in this post (and in keeping with one of my favorite trends in modern paleontology), the new taxon was given a Native American name, in this case Seuku, the name of a trickster from Alsea mythology.
• Horse Diet Through Time in the John Day: My personal favorite study to be published on regional paleontology this summer was by Kaitlin Maguire, who examined stable isotopes from horse teeth through time in the John Day Basin of Oregon.  These isotopes are valuable tools for reconstructing the diet of herbivorous animals, as they indicate the type of vegetation consumed by an individual.  When analyzed through time, they can show whether or not diet changed within a particular group of organisms.  This is especially interesting when looking at intervals of significant climate change, such as the global warming that characterized the middle of the Miocene Epoch, roughly 16 million years ago.  One might reasonably expect that shifting climate would lead to corresponding shifts in vegetation and in herbivore diet, but the John Day horses examined here do not seem to change their diet across the Middle Miocene.  This may suggest that factors other than climate - such as the delayed arrival in Oregon of particular taxa of grass - have played a large role in driving the evolution of ungulates.