Monday, January 3, 2011

Odontocete skull excavation 1

Over Thanksgiving break in 2009, while scouting out a locality for a future permit application, I spotted a nice braincase of a small odontocete skull exposed in a cliff face. The following november, I received a permit, and returned to the locality one year later with my friend Chris Pirrone to excavate the fossil. I knew this excavation would be slightly challenging, because we would be pedestaling the fossil sideways instead of from the top (I have done worse before - I have successfully trenched and pedestaled fossils in overhangs, including an odontocete skull).

Chris excavating the cranium.

Chris excavating later in the morning.

The skull by midafternoon.

By the middle of the afternoon, we had excavated a ring shaped hole around a cylinder of rock which contains the skull. A few pieces broken off (and glued back on) indicated that the skull was very well preserved. However, given the remaining amount of rock, I was concerned that we would not be able to finish before 5pm. Additionally, while excavating on the left side of the hole, I split off a piece of rock which contained a fragment of the rostrum. This indicated the rostrum was relatively long - a scary prospect, perhaps meaning I would have to return and finish the excavation the following day.

Here's the posterior braincase exposed: the right side of the skull is exposed, and the skull is upside down. The right squamosal, and occipital condyle are clearly visible in this photo.

After continued trenching around the cylinder of rock, at about 4pm, the base of the pedestal snapped unexpectedly, and the whole thing came out in one fifty pound piece. The anterior end of the pedestal terminated against an oblique fracture surface; I was nervous that the rostrum may have continued through this fracture. I carved off a half-inch from this surface, and found no bone; additionally, I found no bone in the end of the pedestal. Fortunately, this means the entire skull is preserved within the block.

No comments: