Below you can see what is present of the skull. The rear of the skull is on the left and the dark patch on the right is where the snout would be on a complete skull. We were right about looking down on the palate; however, we realized that we were looking at it from the wrong side, the top! The skull must have been exposed for a long, long time and the entire upper surface weathered away. This is disturbing not only because we have an incomplete specimen, but because the squamosals and skull roof are gone. Thus, it is extremely unlikely that we will be able to assign this specimen to a taxon lower than Phytosauridae.
So....only one way to find out, plus we have put a bit of work into this already. So we decided to collect it. First we apply a separator (toilet paper works fine) to the surface of the fossil and the surrounding matrix. Of course the wind picked up right on time, always does when you are TPing a specimen it seems.
Next we create the plaster cap. Because it is a small specimen we use plaster bandages available from medical supply stores. They are much easier to use in situations like this rather than mixing up a tub of plaster and burlap. Just soak the roll and then apply to the specimen. First we cover the top to keep the matrix together and protect the bones. Then we dig down farther around the specimen and inwards creating a slight pedestal. Then we apply another roll of plaster around the newly created lip. This is called the "collar" and will keep everything from falling out when it is time to flip the plaster jacket and fossil.
Three rolls does it. The plaster needs to dry so we leave the specimen and will return later. Unfortunately a storm is moving in so we cut drainage chutes away from the specimen and cover it up with a plastic garbage bag. This will slow down the drying but is better than saturating the plaster cap with rain and mud.
2 Samuel 21:20
And there was yet a battle in Gath, where was a man of great stature, that had on every hand six fingers, and on every foot six toes, four and twenty in number; and he also was born to the giant..
The "robo-aetosaur" as Dave affectionately calls it, is the holotype specimen of Paratypothorax andressorum Long and Ballew 1985, and if I am not mistaken the actual osteoderms are used in the mount and are completely removable for study (Randy, Sterling, or Jeff will have to correct me on this if I am wrong).
The photo below is one of the dorsal paramedian plates of the left side of the holotype. Paratypothorax is a typothoracisine aetosaur and a member of the clade Paratypothoracisini (Parker, 2007). Members of this clade are characterized by paramedian plates that are much wider than long, have a distinct radial patterning, sharp anteromedial and anterolateral projections, a smooth anterior bar, and a medially offset dorsal eminence or boss.
Paratypothorax is also known from Greenland and the western United States. The best skeleton from the Chinle Formation was collected from Petrified Forest National Park by the Field Museum in 1982. The Petrified Forest specimen was described by Hunt and Lucas (1992) and again by Lucas et al. (2006) who assign it to Paratypothorax andressorum; however, this ID has not been accepted by all workers (e.g., Long and Murry, 1995) who suggest that it may be a new taxon.
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.
thoughtfulness...
Very cool crustacean. Where can I get one? ;)
top photo is from here.
REFERENCES
As you can see the specimen is weathering out along its entire length. The matrix is a muddy, poorly sorted sandstone, crystalline and very hard in some places, and easily friable in others. This will make for a challenging excavation. 
The bottom photo shows where we left off on our first day (2 hours) at the site. We have picked up much of the float outside of the skull perimeter and consolidated loose pieces that are nearly in place. About six or seven centimeters down the matrix gets really hard. Looks to be a three or four day job.
Caption: View Petrified Forest, Lithodendron Wash, Apache and Navajo counties, Arizona. Fort Defiance quadrangle. Chinle formation. August, 1913.
Caption: Chinle formation, Division C, Chinle Valley, near Round Rock. June, 1913.
I will be posting our progress with this specimen regularily mainly because the landowners, who have generously donated the specimen, will be away and thus can follow the excavation here. Of course I hope that my readers will also find this of interest. 
