Project: Corythosaurus

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June 28, 2006 01:33 PM
posted by Lauren Stevens

Preparation has begun and so far I have been able to remove 4 and a half ribs. Most of the ribs have been plaster so far and they come out of the block in many pieces. This is mainly due to many hairline cracks that already exist and because plaster is extrememly soft. I have glued most of these pieces back together so we can keep track of what is coming out of the block.

Removed ribs

I have already come across a few unexpected things in the matrix. There is chicken wire, burlap, 2 different types of plaster, and paint.

The most interesting, and complicating, is straw. This must have been used to re-enforce the plaster to help keep it from cracking, and I must say whoever came up with that idea was a genius - there is no cracking that plaster! I have already spent countless hours trying to remove the plaster with an airscibe and it has hardly changed.

Straw in plaster

I have also come across patches of matrix and bone in unexpected places in the plaster. Most of this matrix surrounds the scapula, and the bone that was found is actually part of the scapula that we didn't think was present. I have covered the edge in Magic Sculpt to protect it from the air scribe. This bone is extremely thin and most of the outside layer (the cortical bone) had erroded away. Also, there is a huge piece of the scapula that is missing, however, since all of these patches of matrix still connect, we have the original positioning of all of the bone and can fill in the gaps. This part will have to be reconstructed, but we fortunately have acurate measurments for length of the scapula.

The scapula is to the right under the ribs. All of the way to the left you can see the magic sculpt, the very dark brown stuff. That is the tip of the scapula. If you look at the matrix you will see 2 different colors - the white is the plaster and the grey is original matrix. You can see how much of the scapula is missing.

June 21, 2006 12:46 PM
posted by Lauren Stevens

I am about to begin work on a new block - Block 4 - and it is HUGE! It is quite exciting! It consists of 17 dorsal (back) vertebrae, thier associated ribs, and a scapula (shoulder bone). Although large, this block should be relatively easy to prepare. The plaster seems thin and the ribs are not actually attached to the vertebrae. I expect difficutly when removing the ribs from the scapula because they are laid directly on top of it and the last 4 vertebrae have ossified tendons running parallel to them that are still in their original matrix. These look like they will be quite a challenge since they are so thin and delicate. We will see!

Corythosaurus Block 4

Scapula with ribs

Vertebrae with ossified tendons

June 14, 2006 05:50 PM
posted by Lauren Stevens

I have just cleaned and oiled my beloved airscribe and have returned it to its home in the cabinet for a short vacation. I am finished with Block 2! It went much quicker than I had expected and am thrilled to have completed my first project. As I continued up the vertebral column I was pleased to discover that the specimen was proving to be more complete and sturdy, but we are disappointed that the bone is not as nicely preserved as thought. There is much restoration in store for poor little Corythosaurus. I will start on another block next week.

Caudal Vertebrae 8-17 with associated chevrons
Notice that most of these vertebrae are attached to each other -there is matrix still cementing them together. Due to the delicate nature in the way vertebrae articulate with each other, it will be extremely difficult to seperate these without breaking them. For now we will leave them articulated.

Caudal Vertebrae 18-28. Chevrons were all carved from plaster

June 09, 2006 04:36 PM
posted by Allen Shaw

Corythosaurus as a wall mount in the old dinosaur hall.

June 07, 2006 02:48 PM
posted by Lauren Stevens

As I began preparation, it has been interesting to learn how the original preparators were able to mount the specimen. They had built a huge support system of small planks, wires, and nails, perfect for housing it in a wall, but a complete nightmare to prepare. It appears that once they had the elements layed out in the manner they wanted, they filled in all of the gaps with a white plaster, thus supporting the wooden structure and the specimen. The plaster, as compared to a rock matrix, is really nice to prepare because it is soft and easy to distinguish from the bone. But it also has many disadvantages. I continue to discover something new and unexpected suspended within the plaster on a daily basis – nails, screws, thick wire, chicken wire, metal rods, rope, and today I found wads of paper. These materials strengthen the hold of the plaster to insure against cracks or breaks, but it also allowed pockets of air to develop where the plaster could not be evenly smoothed out. Now that I am preparing the fossil with air scribes, the vibration will cause the block to split in these areas, sometimes unexpectedly breaking the fossil. I have also come across 3 different colored plasters - white, yellow, and grey - suggesting that the wall mount had been repaired over the years, and several layers of paint – green and brown - proving the mount has been altered at least twice over the years.

A very disturbing discovery that has greatly complicated the preparation and restoration processes is that they had apparently broken the fossils and moved the parts to the position that looked best visually for the wall mount, losing original contact and therefore valuable information about the shape and morphology of the fossils. This is common, and I often find a spinous process in many pieces with gaps filled in with sculpted plaster. Sometimes I can remove the plaster and glue the spine back to its original form, but sometimes there is no real contact between the pieces making accurate reconstruction impossible. Also, since the plaster is so much softer than the bone, the vibration from the airscribe forces it loose, causing many breaks in these processes as I remove them. It can be extremely frustrating.

As I worked up the column I came across a horrible crack that must have been made from a hand saw. The crack itself was probably 1/3 an inch thick and cut through the bodies of caudal vertebras 16 and 17 and the spinous processes of caudal vertebras 12-15.

Caudal vertebrae 16-17 with saw damage

Saw damage through spinous process of caudal vertebrae 12-15

Allen and I deliberated on whether or not to fill the gap before continuing preparation, which ideally would give us the most accurate reconstruction possible. We decided against that and to prepare the separated parts individually because it was clear that over time the crack had widened and an accurate positioning of the parts was no longer possible. This way it will be much easier for reconstruction at a later date. I am continuing to remove the plaster and will soon be able to remove the remaining vertebrae.

May 28, 2006 02:20 PM
posted by Lauren Stevens

I am making my big debut at the museum with preparation of the Corythosaurus vertebral column. Corythosaurus has been living in a wall mount for over 60 years. Many elements of the specimen need little preparation work, but we still have 4 large blocks of serial vertebral elements that are embedded in plaster or matrix. I am beginning with the caudal (tail) vertebrae working from the tip towards the back.

This first block encases about 20 vertebrae, their associated spines and processes, and chevrons. I will begin by removing the block from the wooden support and try to separate this larger block into several smaller ones so that they will be much easier to handle and prepare.

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