31 July 2010

Fossil Vertebrate of the Month: Oncorchynchus rastrosus

Salmon are a symbol of the Northwest, and with good reason: not only have they been a staple food for humans for millennia and a hugely important link in regional food chains for much longer, but they have very deep roots here. Go back to the Late Miocene and you would still see salmon in the rivers of Oregon; you would, in fact, see one of the most impressive prehistoric fish ever discovered: Oncorhynchus rastrosus, the sabertooth salmon. The features that gave the fish its common name (and its original genus name, Smilodonichthys) are its enlarged canines which, arresting as they are, are not as unusual as they might seem, as many modern salmon grow large breeding teeth while migrating upstream to spawn. The size of O. rastrosus, though, is unique: at lengths of up to 2 meters, it was a good deal larger than the largest known Chinook salmon and head and shoulders beyond sockeyes, its nearest living relatives. The sabertooth salmon was in the news this last month (both in the paper and on TV) after a team led by the University of Oregon's own Edward Davis performed a CAT-scan on its skull. The result of this research is a series of impressive 3-D reconstructions, which can be viewed in an online exhibit by the U of O Museum of Natural & Cultural History; if you'd rather see the original in person, it will be part of the museum's revamped PaleoLab exhibit opening this month.

Field Report: Field Camp 2010

As many of you may know, I was the TA for the paleontology portion of the U of O's field camp this year. Since I got back earlier this week, several people have asked me what we did and what we found. I may not be a great blogger, but even I know the first rule of journalism, so in the interest of giving the people what they want, here's a brief summary of what went on (You'll notice that I'm not giving names or locations of any of the work we did; we were at two sites, both of which are publicly owned, and since illegal collection on federal land is a recurring problem in eastern Oregon, I don't want to provide any information that an unscrupulous fossil poacher might be able to use; for those of you who are wondering, yes, we did have the appropriate permits).
The first site we visited (let's call it Site 1, since imagination is precious and should be conserved) was an exposure of the famous John Day Formation, which has yielded one of the largest and best-preserved Oligocene faunas in the world. Since the primary purpose of our trip was to teach basic paleontological field methods, the bulk of our time was devoted to creating stratigraphic sections for the outcrop. There was, however, time for fossil prospecting as well, and it was very - almost ludicrously - productive. Among the things we uncovered were rodents (particularly squirrels and aplodontids), hypertragulids (mouse deer), canids, nimravids (sabertoothed, cat-like carnivores), horses, entelodonts (bearlike relatives of pigs), and rhinos. Perhaps the most impressive specimens we unearthed were four skulls of oreodonts, pig- and/or sheep-like ungulates that were abundant in the late Oligocene of Oregon (we found ample oreodont postcrania as well, some of which are pictured above).
Our second site (being creative once again, let's call it Site 2) was less fossiliferous but scientifically much more interesting. Instead of just getting a handle on the local stratigraphy as we'd done at Site 1, we were also interested in pinning down the age and paleoenvironment of Site 2, both of which were big question marks going in to field camp. Fortunately, the fossils we found were exactly the ones we'd hoped for to be able to assign an age to the fauna: jaws of the canids Tephrocyon and Cynarctoides, teeth of the horses Archaeohippus and Merychippus, the beaver Monosaulax, and a smattering of camels and paleomerycids (antelope-like ungulates). For those of you who know your North American biostratigraphy, that places you unequivocally in the mid-Miocene (~16 Ma), which in this part of Oregon means you're in the Mascall Formation. Pinning down the paleoenvironment was made easy by the discovery of a bird (probably some kind of waterfowl) and by several shell fragments of pond turtles (I won't insult your intelligence by telling you exactly what the students concluded about the site's paleoecology, but if you can't figure out what environment is likely to be represented by waterfowl and pond turtles, I question whether this is the blog for you).
So there you have it: for a trip whose primary motivation was teaching, we had a remarkably successful couple of weeks in the field (and not just in terms of finding fossils; we were very lucky weather-wise as well, though the last couple of days did manage to break the 100° mark). We and our specimens are now all safely back in Eugene, with the latter awaiting curation and, eventually, a trip back east, where they will be reposited in the collections of John Day Fossil Beds National Monument.