Monday, March 13, 2017

Time once again for Girl Scout "Thin...Bones?"

It seems like I have had a run of thin, delicate bones. Perhaps it's just the preservation in this part of the block, or perhaps they were all sorted here hydraulically. I also have a very long gastralia about ready to come out of the same location, almost 8 inches (200mm) long and 3/16" (3-4mm) wide. In any event, I have four bones that have really pushed my expertise in preparing very thin bones.
In the upper left, we have a quadrate. This bone is a link between the mandible (lower jaw) and the skull proper. The jaw articulates on the lower end of the quadrate. Then below it, lower left, is a possible fragment of skull, perhaps back by the quadrate. In the center we have most of the interclavicle (breastbone on humans). Finally, on the right is what I think is a thoracic rib (from the throat area). It has very unusual grooves in it. 

 All four of these have very thin sections, 1-2 mm thick. I have to be very patient and use lots of glue to keep them together. Above is and end-on view of the thinner sections.

 The quadrate is very unusual too. So far I have 3 entire quadrates and 1 or 2 partials. All 3 of the intact bones are very different in proportion from each other. There is a very robust bone (white 3D printed copy below). A second is almost the same proportions but has a much thinner structure, having only about 1/3 of the bone mass in life.  This new one is also different: it is smaller in one direction, but not so in the others. It is like it has been squished flatter. I don't think this is an artifact of preservation - the bone structure does not appear to be crushed. Here they are for comparison in the similar view:

 And here they are showing the significant different direction - only half the thickness.
So I really don't know what's going on - sexual dimorphism? Age differences? 
Anyway, they are soon to go up to Alaska. 
Sincerely, Greg Carr

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