Field of Science

Phytosaur Skull Excavation 3

Here is where I left off on the last post in this series. Jeff contemplating that he did not find the snout when he dug where it should be. As I stated in the earlier post we suddenly realized what we were dealing with. Randy guessed correctly when he stated that "Nature's horse scraper" got to the skull a bit before us!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.

Still not all is lost! Much of the palate is present as are the bases of the quadrates and portions of the maxillae (upper jaws). Even more exciting is that a good portion of the braincase is also present. Although currently understudied it is possible (even likely) that the braincase is taxonomically informative in phytosaurs. I just wonder how much we have.

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.

3 comments:

  1. Oh, and what is that dark spot? Did Jeff pee?

    ReplyDelete
  2. C'mon dude, you know that Jeff is quarry-trained.

    ReplyDelete

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