Restoring a Protostega

Back in October of 2011, the lovable TPI field crew was brought out to a ranch in western Kansas (very near the site of Sternberg's famous "fish within a fish" specimen) to help with the recovery of giant sea turtle. This turtle skeleton will be reposited in the Sternberg Museum of Natural History at Fort Hays State University. The term giant is used loosely here, since the actual turtle was only about a meter in shell length, nowhere near the car-sized members of its genus that would later cruise the oceans. Field photos shamelessly borrowed from Mike Everhart's wonderful Oceans of Kansas website.

Making the hole bigger with power tools. Also shovels.

The turtle site was located fairly low stratigraphically, and was entombed in a fairly hard grey chalk. Our first order of business was to identify the bone layer and then break out the power tools to remove the overburden from a wide area. I'll say it again, that cute little green jackhammer is a backsaver!

Mike Everhart and I jacketing the slab, with the finger hair saving nitrile gloves

Once down to the bone level we perimitered the specimen, cut around with the chainsaw, and jacketed the whole slab.

Perimitering in the quarry

Exposing more of the bones

That was the easy part! Back in the lab we began by using air abrasion and pneumatic scribes to remove the matrix from the fossil, first the individual bones that were collected before TPI arrived.

Individual bone before prep in the lab...

...and after air abrasion, scribe and glue work

A few interesting surprises popped up once I started removing the chalk. Abrasions on the ventral side of the plastron seem to indicate this turtle pulled itself up some distant beach, possibly suggesting it was a female getting to dry land to lay its eggs, though some modern male sea turtles also come out of the water occasionally. The carapace and especially plastron were covered by what look a heck of a lot like puncture wounds, all unhealed. The front flippers were totally lacking any parts below the elbow, in fact one humerus was bitten completely in half. It sure looks like the turtle was a partial meal for a mosasaur like Tylosaurus before it finally sank to the sea bottom.

Abrasion and puncture marks on the plastron

Once the bones were prepared they were all molded individually (when possible). The casts were then manipulated into larger assemblies, where we filled in missing parts and took out some crushing distortion. These assemblies are then used to make production molds for cast copies.

Carapace subassembly in a thixotropic mold

Original bone pile being molded for parts. 

We should have the project done in the next few weeks, just in time to display at the Tucson Gem and Mineral Show this January. Stop on by to check it out!