23 December 2008

meanwhile, back in the lab (part I)...

As temperatures turn colder, it's time for The Excavatrix to turn attention to warmer, more indoor activities -- such as the preparation of mammoth fossils in the lab (not that we excavators aren't still stuck outside... come rain, sleet, snow and hail, excavation marches on...). Lab Supervisor Shelley, her assistant Trevor, and our wonderfully dedicated volunteers have been hard at work on two of the plaster jackets from Zed, our semi-articulated Columbian mammoth.

The first jacket they cracked open: Jacket #91, labeled "mid-vert column." This jacket contains seven of Zed's thoracic vertebra -- a portion of his spine that connects with his ribs. In fact, you can see part of one of the ribs in the photo below, immediately above our scale/quarter.

midvertpartialrib

The proximal ends (the portions closest to the spinal column) of two ribs were encased in this jacket along with Zed's vertebra. And niftily enough, we were able to reunite both ribs with their missing halves:

ribs2

We're always thrilled when we can actually put these paleontological puzzles back together with a minimum of sturm und drang. There are millions of specimens in our collection, and that's not including the bones that have been cleaned but not yet catalogued. The longer we wait to reunite fossils with their broken bits, the more likely it is that the reunion will never happen. In this case, both ribs were deliberately broken in order to make the jacket smaller and more stable, and thus allowing it to protect the vertebrae all the better -- a fairly common practice in paleontological salvage and recovery. However, in many cases, fossils are broken either by the act of deposition itself -- bones collide with other bones and break into bits -- or by accident, during excavation. Asphalt is hard, and mistakes are unfortunately made! These 23 fossil blocks are particularly difficult digging; Deposit 1 in particular is practically cement. So the sooner we can put the bone back together, the better.

Anyway, back to Zed's spine. This particular assemblage is a great example of what we mean when we say "semi-articulated." The photo below is a close-up of one of Zed's thoracic vertebra, and the rib that was found immediately next to it. These two bones would have been articulated, or jointed in life. However, their positions shifted slightly after Zed's tragic end. The two semi-circles would have been joined together in life, but now they're a bit misaligned. Hence, semi-articulated.

midvertrib-artic


Eventually these ribs were removed to allow Shelley et al to finish cleaning the vertebrae. And finished product looks like this:


midvert-finished


Lovely! This jacket is now on display in the museum, by the fishbowl laboratory! Please, drop by, say hello, check it out. More on lab activities next week, holiday schedules permitting.

1 comment:

Spencer said...

Beautiful, glorious...what words can one use? I love the boxes but also feel I am missing so much back at the lab!

Spencer