Thursday, March 29, 2012

Xiphactinus project update

Yep, it's still ongoing.

We have assembled the skull, vertebrae and caudal fin into the mount, and stuck on the first layer of our fake matrix. We remove all matrix from the specimen and make our own for one very good reason: natural chalk is very soft, and is prone to breaking and cracking. It usually offers no meaningful support for the specimen, so it is better for us and the fossil to remove it completely and install our own.

Jacob hard at work filling gaps between vertebrae with epoxy putty
Next up on the docket is to lay out the sets of ribs and pectoral fins, and fasten them to the mount. That process should take about a week, so check back on the next update for progress!

Friday, March 23, 2012

Xiphactinus mounting: The beginning

One of the "nearest forest fires" in the lab lately is getting the world's largest Xiphactinus audax skeleton, RMDRC 08-004 "Mildred" prepared and mounted. These fish are traditionally done as a panel mount, since usually they are a bit flattened, especially with articulated skull material. Single-pieces are preferred since mating up seams on a big flat panel is just kinda ugly. Unfortunately, when dealing with a mount of the biggest of anything, that usually means a BIG mount.
The underside of the skull. We put a support material on this side to stabilize the bones

In this case, the panel is sized to 7 feet tall and 21 feet long, the appropriate size for an 18 1/2 foot long fish. It's going to be heavy no matter what we do, but our goal is to end up with a contraption weighing in at about half a ton or so when we're finished. One can dream.

Just a small fabrication project
We've already finished preparation of Mildred's bones, as well as the needed parts of the "donor" parts fish that would be used to fill in pieces lost to erosion or scavenging sharks. On the 3 fish, we've recovered well over a dozen shed Squalicorax falcatus teeth that were lost when the carcasses were getting scavenged.

Jacob and Lisa bolting the plywood to the frame
The next step is to position the bones on the panel and affix them to the background material. We use some cast parts, as well as the complete skull, vertebral column and tail to get an idea of the size, pose, and margins of the fish. It's always good to figure this out before we start attaching stuff with adhesive. On the downside, it doesn't look very pretty yet, but it gives us a glimpse of how the final product will look.

As of this morning, with the body outline sketched on

 There's still a lot of work to do, but we're confident we can make the deadline now.

Friday, March 9, 2012

Soft tissue preservation in a Platecarpus

This past week we were able to do a bit more work on a specimen that we collected last spring with a student group from the University of Tennessee-Martin. This small mosasaur, a Platecarpus planifrons RMDRC 11-001,  was just about the only recoverable mosasaur material seen on that trip. This specimen was discovered by a UT-Martin student, and the discovery, excavation and recovery process was recorded by a UT-Martin journalism student group.

How many people can you fit on one digsite?
The specimen was brought to the lab and awaited the UT-Martin student group to come to Colorado to prepare it. That chance came this week. The skull was weathering out first, and the roots of nearby plants had started growing around the bone making preparation a bit tricky. The students and film crew covered the preparation of the torso and neck, which was in much better condition. I was left to work out the skull.

Partially prepared torso, neck and head
We were paying special attention for anything that would tell a story about the animal. First we discovered gouges from shark bites on the lower jaw, then a shed sharks tooth at the left articular. While slowly preparing around the quadrate, we located the extracollumnellar cartilage, a semi rigid plate that often gets mistaken for a calcified tympanum. I waas shocked that this was still present with so much root infiltration. later while preparing between the pterygoids, small remnants of the tracheal rings were also discovered. I expected them there if present since they tend to get blown forward through the mouth after death, looking like a linguine dinner after a hard night of drinking. Unfortunately, no skin was present on this specimen, but as always, we'll be keeping an eye out

Can you spot the tracheal rings?

Tracheal rings in another specimen, this time a Clidastes

Friday, March 2, 2012

The things you find when you work on stuff

Mildred's skull, with blue tape to mark parts that need to be removed
We've almost entirely finished the preparation of RMDRC 11-021 "Lois", the last parts donor fish for our reconstruction of RMDRC 08-004 "Mildred". We've been going through some of the pieces of chalk that fell out of the huge main jacket when it partially collapsed when we flipped it for removal from the digsite. Sometimes these things happen, especially when the chalk is weathered and fractured.

Feathery and fine gill structures articulated with the arches
Surprisingly one of the chalk pieces produced something very rare: the actual preserved gill structure of this Xiphactinus. Usually with most Xiphactinus specimens, the disarticulation of the skull by scavengers results in these delicate structures being lost. On articulated skulls, they are likely present however no one ever starts removing bones to investigate if they are indeed there. For now they remain pretty rare things. We won't be using these in our restoration, hopefully we can find a good home to donate them to.

Jacob and Lisa fastening plywood to the steel tube frame

In other news on the reconstruction front, we've finished building the frame for Mildred. 21 feet long, 7 feet tall, it's going to be 150 square feet of big bad X-fish. Nearly time to put it on a rolling stand so we don't have to lift it ever again!