Monday, May 30, 2016

One Mystery solved - it's a jaw fragment!

I've been working on a small block that is check-full of bones. We started uncovering a skull fragment last week, and I thought it was part of the top center of the skull, along the midline of the pineal gland. This afternoon took it off the block.

Now that I've got it off it is clear that it is something else - it's about 2/3rds of an upper jaw, left side! There are lots of teeth, or at least teeth roots, and the lower part of the nasal passage and the hard palate. The hard palate has a different shape that the one in the original skull which is apparently broken. This one is more intact.

I'll have to wait until I get back to OMSI ( I'm sick this week) to finish the teeth with a Paleotools #2 - my modified Chicago Pneumatic air scribe is just too damaging for the teeth. I learned long ago that the teeth are so fragile that only the most delicate tools can be used.

This fragment of jaw may be from the other half of the semi-skull we already have, or may be from a different one. We'll have to take some accurate measurements to tell.

Anyway, it's great to get more teeth. It has been about 2 years since we found a fragment with teeth and/or teeth roots.
Sincerely, Greg Carr

Wednesday, May 25, 2016

Two more skull pieces!

So right now I'm working on a block at home and a block at OMSI. The block at home was originally located close to the original skull, about 10 inches (25cm) away. It is a lovely little block with a whole cluster of centrum (backbones) at one end, plus most of a large neural arch with some ribs thrown in for good measure. I think there are 8 or 9 centrums. Although they look like they are articulated, they are not. They are different sizes and orientations so they came from different individuals or different parts of the backbone. Too bad. Anyway, I was going to keep the block pretty intact and leave it as an esthetic piece since we already have good single specimens of all these bones.

At the other end of the 'home block' there were initially two small fragments of bone glued back on. The way this works is that a smaller block is broken off a larger block so we can work on it, usually along natural fracture lines. The bones that cross the fracture surface are removed from the smaller block and glued back onto the other block, so that the bones are made whole again. So we started out with two small bone fragments separated by about 3 inches (7.5cm). Preparing these small pieces of bone did not immediately make clear what they were. But it did become clear that they were parts of the same bone. One side of the bone is now prepared, and it is another section of a skull centered around the pineal gland. I think this makes it the 5th specimen we have from this section of skull! And first measurements indicate that it is the largest to-date! It is amazing how a piece of bone 5.5 inches (14cm) can hide in a block of rock almost completely when the rock is only 7x10 inches!

So I'll have to remove this skull fragment from the block for scientific study. The other end with all the centrums can remain intact as a showpiece, unless something else comes up!

As for the other skull piece, it's at OMSI. I started on a new section of block 1 and uncovered the end of a strange item. I couldn't really tell if it was a piece of bone or a piece of coral. It was not as dark as normal bone, but had the correct internal structure. It did not power up black when touched by the air scribe - it was grey like coral. I decided to treat is as a bone . I'm glad I did since it turned out to be a nice limb bone.  There was a 'small spine' next to the limb bone that looked like a neural arch. 

When I got the limb bone undercut and ready to remove there were some small scraps of bone showing at the bottom of the cust. After knocking off the limb, I realized that I had broken completely through the lower end of the 'small spine". It is not a neural arch, as it is rapidly expanding into a big section of bone. It is a piece of skull, I think it is the middle along the centerline. We will tell more as we excavate more. Unfortunately, it will require practically cutting the big block completely in half as it is imbedded directly in the middle, pointing straight into the center!
Sincerely, Greg Carr

On the left we have the skull piece  - the reminder is still in the block. The right piece is the limb bone. 

Monday, May 23, 2016

Back in the Saddle Again - Recreating a full skeleton

I've taken off several months from writing the Blog since I had a lot of things to do this spring - doing taxes for H&R Block, refurbishing a rental house, letting my right hand rest from air-scribe work, etc. But I'm back and proceeding at full speed ahead! (to mix metaphors)

I've been working at recreating a full size skeleton of a Thalattosaur. As readers of this blog know these bones are scanned before being sent off to Alaska for study. I can scale them in X,Y or Z dimensions using the 3D printing software. I have now printed out a full set of backbones based on a well-preserved Centrum+Neural Arch  specimen from Bernie. I scaled them and numbered them based on a well-preserved Miodentosaurus Brevis skeleton from China. I then added some 1/4 inch (6mm) foam pads to mimic the disks between the vertebrae. The resultant skeleton is about 13 feet (390cm) long. I'm not too worried about the exact length - we have bones of animals from 2 feet to 30 feet (0.6 to 9 meters) so any animal in that length range would be representative of a proper Thalattosaur. There are some significant challenges to printing out a 30 ft skeleton, however!

Next most common bones are Ribs. I made up a full rib in cedar wood, again based on the Miodentosaurus, since all the ribs recovered here are broken. I then made a silicone mold and cast about 52 copies! Boy, that sure is a lot. These copies will be shortened to match the Mio... bones and then mated up to the appropriate body vertebrae. I have chosen to hook the ribs to the centrums with small supermagnets. That way the ribs are removable for transport or storage.

The centrums themselves are strung on steel rods passing through holes where the spinal cord ran in the original bone.The rods are slightly less than 4 feet (102cm)  long so they will fit in a 'standard' display cabinet. This way the skeleton can 'swim' through 4 sequential cabinets at rock shows. It also makes it much easier to transport.

After the ribs I'll be working on tail chevrons and limbs. I will be attending a  National Federation of Rock Club show in late July, and Eric Meitz will be presenting at the SVP (Society of Vertebrate Paleontology) in October. I hope to have the skeleton, in whatever state it is, displayed at these shows.

I'm also preparing still more bones from the original matrix blocks. One of the original large blocks 200+ pounds (100+ Kg) is yielding another nice limb bone. I'm also working on a smaller block at home where I have a nice boom microscope. In a block about 10 inches (25cm) I have at least 8 centrums, two neural arches, two rib sections, and a very nice skull fragment at least 5 inches (12cm) long! And I have yet to expose all the bones in it! That will be for the next post (soon) I promise.
Sincerely, Greg Carr