Sunday, November 24, 2013

Proof of multiple skeletons - another type of backbone

It looks like we have some proof of a second type of animal's bones in our specimens. So the dilemma of the week is: what do we call this pair? Bernie and Ernie? Bert and Ernie? Bernie and Bertie?

We have prepared a second type of backbone that is very different from the squished hockey-puck centrums typical of Ichthyosaurs. We have quite a few of the latter type which is what led us to believe we had an Ichthyosaur in the first place. It is about 57mm long by 44mm wide. No processes (spurs) are evident, and I don't see where they would have been if they got worn off. It does have very nice zygapophyses, the interlocking parts between the backbones. There is a large crack across the bone, filled with substrate(coarse sandstone& chert chips) , so it broke during burial. This crack is evident as a broad curved line in picture #1. The squares on the card are 1/4 inch.
Here's the pictures:

Ichthyosaur-type backbone for reference:

 At this point I'll predict that the new type of backbone belongs to the skull, which doesn't look like an Ichthyosaur either. Hopefully we'll have some more backbones of this second animal as we go. Some of the limb bones might be from this second animal as well. The limb bones prepared to-date have hollow ends, indicating the animal was not mature. However we have at least two bones in the matrix that have rounded ends that are not hollow. These would go with the second animal, I believe.

On the original animal, we have previously prepared a Humerus  (or Femur). We now have a second similar bone that is slightly shorter. It also has an interesting ridge across one end that the first bone does not have. So I'll predict that we have the Femur to go with the original Humerus. This means the Ichthyosaur-type animal had 4 distinct limbs, like a lizard-shaped Ichthyosaur like Cymbospondylus. It's not completely prepared, so I'll post pictures of both bones next time.
Have a happy Thanksgiving for those in the US!
Sincerely, Greg Carr

Tuesday, November 5, 2013

Multiple Skeletons?

Bernie the Ichthyosaur - Possibly multiple skeletons?

The last couple of weeks have seen us remove a lot of fairly barren rock (not a lot of bones) from around the skull. We have exposed a very interesting backbone / neural arch that does not look like any bone we've recovered yet. And we have a miniature vertebrae that may be from a very young Ichthyosaur!These finds may be telling us that we have multiple skeletons, not just one. 

First of all, the interesting backbone. The bone is located adjacent to the snout of the skull. It has very prominent pre or post zygapophyses (I can't tell the difference yet). Yes, I had to look it up too - certainly qualifies for the word of the day! .  These are the parts of the neural arch that rub on the preceding or following neural arches. The difference between the porous bone, where the cartilage pads were, and the smooth bone where there is no cartilage is very clear - excellent preservation!There is another bone immediately under the neural arch that will have to be co-excavated to prepare it. So far, it doesn't look like an Ichthyosaur backbone, so it may be from another type of animal. This strengthens the case that we have multiple types of animals in this block, as unlikely as that seems. 

So indeed we may have Ichthyosaur bones and other bones in this block. Now, how about two Ichthyosaurs? 

During this preparation we have been finding very small, fragmentary bones that resemble cylinders 1 or 2 mm in diameter. These are short, about 1-2cm long. We don't know what they are, but they certainly seem out of scale for the other bones we've been finding. Here's a couple pictures of the bones partially excavated (too fragile to remove completely) . One is on the Coracoid with a scale for reference. 

And here is one for a normal rib for comparison. 

However, about 3 weeks ago we excavated a perfect Ichthyosaur centrum, about 6-7 mm (1/4 inch)  in diameter and length! These photographs are taken through a preparation microscope eyepiece, and the circle diameters are 6 and 7mm respectively. The centrum even has the flattened facet for the neural arch (shown in the pictures). 

So - do we have an infant, or is this a bone from the very end of the tail? I don't know but it's very interesting. 

We also removed a bone that appears to be part of the snout, again located close to the snout of the skull. It needs significant preparation under the scope. Apparently there are no teeth. There are two Ichthyosaur centrums under it to be prepared as well. 

Sincerely, Greg Carr