Thursday, July 11, 2013

Fourth post - second update on the preparation

Preparation update, Bernie the Ichthyosaur, March 16, 2013.

Progress on preparing Bernie the Ichthyosaur continues apace. Most of the work this past month focused on preparing a Coracoid that will probably be important in classifying the animal. The coracoid was in poor shape, being split between three separate blocks of rock. The blade had been split down the middle, through the largest plane of the blade, leaving two thin sections on different rocks that individually were too thin to prepare.
   In addition, the thicker section of the Glenoid side of the coracoid (the joint to Humerus) was on a third rock. Many small bones were uncovered during the excavation process, including two neural arches and parts of centrums.  Eventually, all three sections of the coricoid were partially prepared and glued back together with a filler of epoxy to make up for material lost during breakage. The exterior of the bone was then cleanly prepared, restoring it to the original dimensions. Only a small amount of distortion in the finished bone is noted. One small spine was left on the surface as it’s too delicate to prep out. This was a very satisfying job.
A second important bone, a humerus, is currently being prepped. It too was found in three rocks. The proximal end (end nearest to the body) has been prepped, as it was almost entirely free anyway. The distal end (end away from the body) is being worked out. It is adjacent to a rib bone, and I may leave them joined on one block of rock instead of separated.  [ I did end up separating them] I think I can recover more of the curved end of the rib from another block of rock. 
Both ends of the humerus have a conical hollow in it, without any fill. I left the matrix (surrounding rock) in them to support the thin edge of the bone. I suspect it had an extensive cartilage fill, and was probably not ossified. Several other arm bones that are not totally prepped out yet show the same condition. Perhaps this was a young animal? Also of note is there there is no anterior flange – the shaft is completely round and symmetrical. I haven't found any species of Ichthyosaur where the arm bones are not flattened - stranger and stranger! 

Sincerely, Gregory Carr

1 comment: