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.

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