Recently found while cleaning bulk matrix from deposit 1 in the lab, this is a dentary of a juvenile dwarf pronghorn, Capromeryx minor. It is probably the youngest pronghorn individual represented in our cataloged collection.
The paper, entitled "Paleoecological and taphonomic implications of insect-damaged Pleistocene vertebrate remains from Rancho La Brea, southern California," will be published in the journal PLoS One on July 3, 2013
After a month of digging in Box 13 we have almost completed one level (25cm) and it has continued to be a deposit packed with many fossils. The above image shows what we are working on this week.
We opened our 9th Project 23 box last week! This one is part of deposit 13 and is located on the east side of the compound, being shaded by our La Brea Tar Pits Museum canopy. Many large vertebrate fossils were exposed at its surface, including the back of a saber-toothed cat skull, a saber-toothed cat cervical vertebra, dire wolf teeth, large bird bones, and large herbivore long bone fragments and teeth. A condor-sized humerus and juvenile horse tibia are among what has so far been excavated. Box 13 is another deposit packed with well preserved fossils!
We are excited about a new addition to the list of species recovered from Project 23. Our first record of the freshwater limpet Ferrissia walkeri was found in the matrix from a sloth skull excavated from the Box 7 series. This well preserved complete specimen is the first mollusk species that Project 23 has added to the Rancho La Brea faunal list. Ferrissia walkeri is known from other Late Pleistocene localities in Southern California and is usually found in fragments because it is fragile.
The excavation of the main vent deposit in Box 1 is done! We have been excavating it since August 2008 and measured out 14,000 fossils from the four main grids of the deposit. That is just a preliminary number of fossils from those grids. The number of fossils will multiply significantly once the matrix has been processed due to the high concentrations of microfossils preserved that were too small to measure. All that's left where the main deposit was is a sticky pile of burlap that was used to support the deposit's bottom. The rest of Box 1 is currently on hold.
Aside from digging fossils at the tar pits, a preparator’s position description includes “and other duties as necessary.” A couple weeks ago, this included rescuing the floating lake pit mammoth! It had drifted south from a broken anchor and ended up mired in sediment by the sidewalk bridge, looking as if it were calling out in distress to passersby. We could have put a sign up that said "Please don't feed the mammoth!" But it really belonged back with its family and operations needed our assistance with its rescue.
The above image is a kangaroo rat (Dipodomys sp.) right dentary, another notable specimen from Box 14 microfossil sorting. The roots of its inscisor and cheek teeth are partially exposed. There are 12 living species of Dipodomys in California, with eight being in Southern California.
Recently found in Box 14, this is a Harlan's giant ground sloth, Paramylodon harlani, right premaxilla, which is the part of the skull that supports the upper lip. It is the first sloth premaxilla to have been found in Project 23, and a rare element to find at Rancho La Brea. We have also found the back half of a sloth skull, vertebrae and ribs in the same deposit.
We are currently focusing on washing matrix just from Box 14 because its asphalt saturated sands contain thousands of microfossils! The image above shows an example of what we have been finding during sorting.