Phytosaur Skull Excavation II

On Wednesday we returned to our phytosaur skull excavation which I first featured on April 14th. Since that time there had been a late spring storm with some precipitation, but the site was covered and fine. The photo below shows the site as uncovered and us continuing the trench around the specimen.

Several pieces of float on the surface were portions of the upper jaw (maxilla) and Jeff set to work piecing it back together. The alveoli (tooth sockets) are clearly visible in the picture below.

Strangely when this piece of maxilla was fit back onto the in-situ specimen the alveoli were facing downwards (see photo below). This was troublesome as the ventral portion of the skull was exposed on the surface. We wondered if we could actually have part of the lower jaw; however, the fragment is definitely not from the lower jaw. Maybe the skull was distorted and the maxilla has disarticulated and flipped around? Extreme distortion of phytosaur skulls is actually common, they often deform plastically and can be flattened, skewed, and even twisted. One specimen from the Chinle has the snout folded tightly like an accordion.

Still, nothing to do except keep on trenching and get ready for the plaster jacketing. So far we have been able to do all the work with pick, shovel, and cold chisels. There appears to be a mud layer in the sandstone just beneath the skull that makes the digging easier.

However, we were starting to get clues that maybe all was not well with this skull. We had a hypothesis and to test this we trenched across the front where the snout should be and found...nothing (see photo below, snout should have been under Jeff's left leg). So far we have the rear portion of the skull, braincase, and palate exposed and an "upside down" maxilla. It quickly became apparent what had happened here, but I will leave that for you to guess at and will reveal in the next post in this series.