Friday, September 27, 2013

We have the skull with teeth - but is it an Ichthyosaur?

The mystery of the 'mystery bone" has been solved - it definitely is the skull with teeth in place in the upper jawbone! 

The big bone we've been chasing out for over a month is definitely the skull of the animal. Just Wednesday (9/25/13) we uncovered three, possibly 4 teeth in place in the end of the upper jaw. Uncovering the others will need to be done under a 15 power scope as it's just too nerve-wracking to try to do it with a 3 power head-mounted magnifier. This is because the teeth are the exact same color and texture as the small chips of chert common in the matrix, and you can't tell the difference without significant magnification. So we'll rig up the boom microscope over the big block and go for it next week. 

The smaller pointed bone to the right of the snout is a neural arch, not part of the skull bone. It looks like the skull is mostly intact (the right side, at least) although the snout is broken it is nearly in position. It appears to be quite broad toward the back, over 200mm (8 inches) wide as over 50mm are already exposed and we're somewhere toward the mid-line of the skull. It's about 300mm  (12 inches) long as exposed. It will take us several months to get the skull out, as there is lots of rock to pulverize and remove to get it out. A nice Christmas present maybe. 

Stepping back from the excitement, this skull and the other bones, taken as a whole, present a great dilemma and discovery. The skull does not look like an Ichthyosaur - more like a crocodylomorpha (triassic crocodile ancestor)  It has relatively small eyes. I'm not sure which hole is the orbit (eye socket), but it looks like the closed hole in the middle is the best guess, and the curved arc in the back would be the rear of the skull. Whichever hole it is,  this animal did not have large eyes like Ichthyosaurs. The shape of the skull is more like Croc. The arm ones are long, again more like a Croc than an Ichthyosaur. Countering this, the backbones and ribs are very much like an Ichthyosaur, not at all like a Croc. There are no scutes (ostoderms) - bony plates armoring the skin of Croc. The teeth are like an Ichthyosaur. We probably don't have two mixed skeletons. All the visible backbones on all the blocks (not just this first block) are like Ichthyosaurs. My guess at this point in time is that we have a new, very basal Ichthyosaur showing many characteristics of ancestors less adapted to fully marine life. On the other hand, it may be a marine Crurotarsans, or very early sea-crocodile like Thalattosuchis, although they are known from the Jurassic and Cretaceous. This would be earlier than that, as it's Triassic!

Quoting from Wikipedia "Thalattosuchia is the name given to a clade of marine crocodylomorphs from the Early Jurassic to the Early Cretaceous that had a cosmopolitan distribution. They are colloquially referred to as marine crocodiles or sea crocodiles, though they are not members of Crocodilia."

Here's a triassic Sebecus icaeorhinus -Crocodylomorpha  - some simularities are obvious.  

Here's an animation taken from still photographs showing the skull excavation. It shows the block before any of the skull was exposed and ends up with the above large picture. I've had to make it small to be uploaded, it's still 80 megs so please be patient. 
Stay tuned for more updates. I'll be posting about the 'tools' of the trade soon, telling you how we actually do the preparation.
Sincerely, Greg Carr

Friday, September 20, 2013

Mystery bone gets larger, one strange bone possibly identified

Another quick update about Bernie. We have been working for several weeks to get a bone and ammonite out from between the large Nautiloid to the left (bottom in this picture) and the large unknown bone, probably part of the skull, to the right (top in this view) of a large gap between stuff in the center of the main working face.
Well, we finally have them removed. The bone that was removed is very interesting, It resembles a folded premade taco shell, with smooth bone surface as the tortilla and a filling of bone and matrix with a hollow surface. It has hole through it. It is roughly square about 6 cm on a side and about 2 cm thick. One side is a curved bone surface from front to back. The other 3 'sides' look like the hollows found on the ends of the long bones - hollow cavities with knife-thin edges of bone lining them. What I think we have here is a fused ischium/pubis bone like that found in an Ophthalomosaurus (Handbook of Paleoherpetology,m Vol 8, pg 40) with the edges facing other bones incompletely ossified. 

This bone will require some more cleanup on the incompletely ossified sides, but is certainly one of the more interesting ones! The bone along the rim of the 'taco shell' is less than 1mm thick!

This has exposed much more of the very large bone that I suspect is part of the skull. We have 'chased out' the bone along the larger axis, and found it connects to a hollow on the original outer surface of the concretion that had bone showing. It stretches the full width of this picture - over 30cm long. It is well over 10 cm wide and we haven't found the inside edge. Jerry and I both have spent a full day excavating barren matrix from the outside edge of the block, and we'll have several more weeks removing it. This matrix (here at the top of the picture) will all have to be removed to get at the 'outer' edge of the large bone, and eventually behind it. There is one centrum (backbone) at the right end, and another Nautiloid is appearing at the left end, both to be watched and removed as possible. The top of the larger Nautiloid was removed to allow us access to remove the ischium/pubis, and it's being kept safe for re-attachment (probably this next week). 
Several other smaller bones have been removed and need to be cleaned up as time permits. 
More updates. As I tell folks, the work is meticulous, but not tedious - it's always a challenge and very interesting. Sincerely, Greg Carr

Tuesday, September 10, 2013

Mystery Bone

August Update

Today's post will be brief as no work was done on Bernie in August. Both myself and Jerry, the two OMSI volunteers working on the beast, went to Como Bluff Wyoming on a week-long dig for the Tate museum in Casper, Wyoming. There was 8 or 9 people at the dig (depending on the day). In total we removed and packaged 22 bones. One my be an Allosaurus brain case or Camarasourus jaw. We won't know for sure until it's prepared. We also got Stegosaurus ribs, several partial teeth, and several unknowns. Also I spent a week on Vancouver island, BC, gathering Cretaceous plants and ammonites, and collecting trilobites from the Spence shale in Idaho and fossil fish at Kemmerer, Wyoming (Green river formation). So most of my time was field collecting work, not inside in the lab at OMSI.

Back to Bernie. We have been working on clearing matrix from around a rather large bone that may be part of a skull. It's rather hard to visualize what it is, but a semi-circular notch on the right side may be a partial eye orbit. Here's a couple of pictures.

It is over 165mm (6 1/2 inches) long, 85mm (3 1/2 inches) wide, and very thick in places. I still think it's part of the skull, though I can't place it. 
Can you?
There is another bone on top of it that may be a skull part, too - bottom left in the picture. Also bundled in there is the large Nautiloid, a medium sized centrum, a partial rib, and another bone directly under the bone on top of it. These are all touching each other at some point!

So we have a large mystery bone. It will be several months before it's out, what with moving all the bones on top of it and removing about 2 Liters (1/2 gallon) (minimum) of rock to get access behind it. And we still have to get behind the scapula and a long bone to get them out, too. 

All - in - all, good work to look forward to. 
Sincerely, Greg Carr