Friday, December 24, 2010

New Photo Gallery Collection

I've created a gallery of my paleo images including photos from the skin impression test session from my earlier post. Visit my Zenfolio Paleo gallery. Larger image sizes are available for viewing there.


Photo Test of Hadrosaur Skin Impressions

I've personally found the dinosaur skin impressions we've had in the lab particularly exciting. Seeing the texture of scales and scutes evokes living, breathing, and dying creatures in a way that bones alone don't do. At the Utah Museum of Natural History, we see a lot of hadrosaur skin. Mike Getty tells me that hadrosaur skin impressions are more common than for other dinosaurs. That may say something about the toughness of hadrosaurine hide. And it seems that the fossil hadrosaur sites in Utah's Grand Staircase provided especially good conditions for skin impression preservation.

Last night I did some test photography on some large skin areas with cast (positive) and mold (negative) impressions of hadrosaur skin. Scales, scutes, and skin wrinkles are recorded in sandstone. The image below is a mold impression. You can see scale texture and a row of scutes that studded the top of the hadrosaur's tail. Each scute was located above the neural spines of the duckbill's vertebrae.

I wanted to work out what kind of lights to use and how best show the skin texture. It's difficult to use a very shallow angle light and get good exposure across a large specimen. I've masked out the lab background and sandbags that support the pieces. This is a perspective view with the distal end of the impression at the top of the image. There are more puzzle pieces we can fit into place for the next photo session.


Thursday, November 18, 2010

Jersey as sauropod fan-prophylactic?

Dinochick has a fun post with video of a Chicago Bears fan scaling the Field Museum's outdoor Brachiosaurus mount. Obviously the museum forgot to dress the sauropod in the proper jersey. Back in April the Brach sported appropriate Blackhawks attire. I think a proper jersey may have foiled the drunken dino-jockey, but I may be underestimating the ingenuity of drunks.

Friday, September 24, 2010

Kosmoceratops Artist's Interpretation

My Simpson's-style take on Kosmoceratops richardsoni à la Sideshow Bob.

Wednesday, September 22, 2010

Kosmoceratops richardsoni skull — prep lab photos

Here's a repost of a photo of Kosmoceratops in the Utah Museum of Natural History prep lab, along with another image from a different angle. When I first saw the flaccid dreadlock frill horns, Sideshow Bob came to mind. Click on the above images to enlarge.

Here's a link to the Kosmoceratops richardsoni/Utahceratops gettyi paper at PLoS ONE announced today.

A fun post at Dinochick Blogs summarizing and reacting to the new Utah ceratopsian papers.

Press release page at the UMNH website.

Congratulations to paper's authors and special congratulations to Mike Getty whose monumental efforts are recognized in the naming of Utahceratops gettyi!

Monday, September 13, 2010

Wax off — mini heat gun

Removing the water-soluble PEG wax turns out to be better done with heat first, then using water for cleanup. While the Carbowax we've been using is indeed water soluble, it's not easily water soluble. If a specimen can't handle extended saturation with water and perhaps some scrubbing with a toothbrush, be aware that the wax doesn't melt away easily with exposure to water. I suggest thinking of the water soluble quality of the wax as lending itself to final cleaning of a thin remnant from the fossil's surface.

The bulk of the wax needs to be removed manually, and I've found heat application to be the best option that's easiest on the specimen. I melt the wax and wipe or wick it away. When I get to a layer of cheesecloth reinforcement, I melt the wax and then lift the cheesecloth away from the bone incrementally. Once nearly all the wax is removed, careful water cleaning then removes residual PEG wax. So your specimen needs to be able to hold up to some water exposure and to heat exposure of a few hundred degrees. I'd be concerned about using heat to remove the wax from partially mineralized recent fossils (not something we deal with in this lab).

I've found a good, inexpensive portable tool that provides controlled heat without live flame. The Micro-Therm Flameless Heat Gun can be found on the web for arount $20 (list price from the Solder-it website is $24.95). It comes with a butane lighter without a flint wheel that serves as a fuel reservoir. The lighter has a refill port and apparently you can use regular lighters in the tool as well.

There's a nozzle attachment that's designed for using the tool with heat shrink tubing. I can attest that it's works well for that job. Fossil prep and electrical repair with the same tool.

Monday, July 19, 2010

Wax On. Wax Off?

In April, Lori and I had the privilege of attending the Third Annual Fossil Preparation and Collections Symposium at the Field Museum in Chicago. One workshop we attended introduced us to the concept of using water-soluble wax to support delicate areas of specimens while working on them. Debbie Wagner showed us how PEG (polyethylene glycol a.k.a. Carbowax) can be used with and without cheesecloth reinforcement. We were also introduced to cyclododecane, a wax that sublimates in air that's suited for specimens that can't be washed in water. Carbowax is much easier to find and much cheaper, so as soon as we got back from Chicago I ordered some wax from Museum Service Corporation. They carry Carbowax 4000 for $22 per kg. available online.

Lori has been working on some Ghost Ranch material with tiny bones and scutes, and I've been working on an ornithomimid which has long, delicate spines on the caudal vertebrae. Months after the Chicago trip, we finally decided to try using the PEG 4000 wax on a couple of delicate bones.

We had to figure out how to deal with molten wax in the lab. I tested the melting point of the wax and found it didn't need an expensive lab-grade hot plate to keep it liquid. We found a very inexpensive solution while at (apologies) Wal-Mart. We were looking for a small crock pot or hot plate with temperature control, but we settled instead on the candle warmer in the photo above. The warmer is designed for use with jar candles, so we picked up a candle and a warmer (under $15 total). At home, we melted the candle to get an empty jar, and tried melting the PEG 4000. The warmer will melt the PEG very slowly, but it's perfectly suited for maintaining the wax as liquid once it's already melted. The warmer has no temperature control, and it doesn't get hot enough to be scary in a busy lab. Since we don't have a lot of time in the lab to wait for a very slow melt, we melt the wax in the oven at home and then use the candle warmer to keep the wax liquid while we're at the lab. We use low temperature oven at home, 200° F or less — well below the flash point where the wax can catch fire. We transport the wax in a small, soft-sided lunch box cooler and the wax stays liquid for the half hour before we get set up in the lab.

The above photo shows wax and a small piece of cheesecloth applied to a delicate caudal vert. At the Field Museum, one application tool they use is a pair of tweezers with the ends held closely together. Lori's holding a ruling pen above.

The tweezer applicator technique reminded me of the ruling pens I used to use for drafting and design work, and I think a ruling pen is ideal for controlled wax application. It's easy to adjust and hold and will maintain the gap you choose indefinitely. I leave the pen in the molten wax so that it warms up. The warm pen keeps the wax molten while I work.

This image gives you an idea of how delicate the spine is. The matrix is hard and I had to use an air scribe to remove it from the exposed bone surface. With the wax holding the structure together, I was able to much more easily do this delicate work. I've consolidated the cracks visible in the spine, but haven't removed the wax yet. I want to show this to Mike Getty and Eric Lund before I put water to the wax.

Lori's using a thin bead of wax to stabilize a very thin bone in her Ghost Ranch cast. She's also stabilized a fragmented scute so she can remove surrounding matrix.

Thanks to the preparators at the Field Museum for teaching us this technique. I hope that the cheap candle warmer and the ruling pen applicator are useful contributions.