Wednesday, September 26, 2012

More with Avaceratops

We just got back from the final dig of the 2012 season in the Avaceratops quarry. The weather was outstanding with sun, highs in the 80s and lows near 40. Getting a little chilly in my tent, but nothing uncomfortable.

A few of the epoccipitals. Not very big or pointy.
When we decided to take a jackhammer to the overburden we had only recovered some postcranial elements and one part of the frill, the right squamosal. Many hours later we had blasted out several tons of rock from above our bone layer, and were able to get digging.

The smallest group jacket, with at least 4 bones
To our surprise, nearly all of the bones found in this expansion of the quarry were disarticulated parts of the skull, including some parts that had never been seen before in this genus. We recovered (so far) 8 epoccipitals, the predentary, and a complete jugal (all new), plus both postorbital horns, a left dentary, nasals, maxillae, the other squamosal, and both splenials. There are even more bones in the blocks that we couldn't get a good look at yet, so completeness should further increase.

left Nasal, very well preserved

inside of right maxilla, with a few teeth still in place
I am interpreting the site as a logjam along the southern edge of the quarry, made of (now) carbonized conifer trunks and surprisingly the limb of a very large hadrosaur, the femur measuring a whopping 1.25m long. Check back for more photos as prep continues, and stop by the lab for a look if you are in Woodland Park!

Thursday, September 6, 2012

Digging Avaceratops

It seems just a week ago I was in the badlands of central Montana picking at bones in concrete-hard sandstones of the Judith River Formation. The locality we worked at the end of our trip is known for a nice productive channel lag deposit that gives up claws, teeth, and moderately sized dinosaur bones. Occasionally there are more than a few bones in one spot. We happened upon one of these spots in the lag and discovered a partial skeleton eroding out of the bottom of the exposure. Already a good find in the difficult to scout JRF.

The author, picking away at hard rock

The beginning of opening the quarry

The bones turned out to be from a single Avaceratops, one of the rarest horned dinosaurs in the Judith River Formation. We recovered what bones we could from the hard rock using hand tools, and plan on returning to the site at the end of the month with heavier equipment to get down to the bone layer. So far we've recovered parts of the skull and skeleton yet surprisingly no vertebrae. Hopefully much more of this animal is locked safely in deeper rock.
The right squamosal
The same bone, showing the 3 characteristic bumps
This is a fairly small juvenile specimen, probably only 12 feet (4m) or so in total length. Two of the elements that we recovered tell us this dinosaur is Avaceratops: The squamosal (part of the bony frill) has a series of distinctive bumps on its lateral surface that only happens in Avaceratops. The second bit is a tiny ungual (hoof) of the 4th finger, which is lacking on all other North American ceratopsians.

Scapula and coracoid in preparation

Check back with us and see how the excavation goes. We will be bringing in our trusty electric jackhammer and air tools to open up the quarry. We should know more about what is present beginning in October.