31 October 2008

weekly update: happy halloween!

We here at Rancho La Brea pride ourselves on our holiday spirit.

Michelle. Devilish excavatrix extraordinaire.

Unfortunately, Michelle took her Halloween persona a little too seriously today, and placed a hex on grid B-1.

The face (and index fingers) of evil.

Because ever since SHE worked in B-1 yesterday, we've come to a near standstill in fossil extraction. All of the bones are intertwined with one another, and completely STUCK in place. The big dire wolf skull is stuck on top of the lion skull, and the sloth vertebra is stuck next to the dire wolf skull, and the saber-toothed cat humerus is pinning the vertebra in place, etc etc etc. It is a veritable portrait of frustration. Observe:


Curse you, devilish Michelle! And curse you B-1!

This week's tally:
-33 bones extracted, including that juvenile saber-toothed cat skull fragment:

Shelley's Halloween costume: hand model!

At first, we thought we'd broken the saber during excavation, but after closer inspection, it looks like the hole in the center of the tooth is the natural result of pit wear -- the erosion of bones caused by other bones as they all jostle around in the tar pit.

- We also got the second-to-last dire wolf skull out:

Photo by Michelle.

Happy Halloween!

28 October 2008

weekly update: dogs and cats, living together, mass hysteria!

Yeah, it's messy, but does your office have lightsabers and power tools on the same shelf?

We're gonna try to make this weekly update thing happen, like, every week. On Fridays. But not this past Friday, because Blogger ate my last update before it posted properly (curse you, Google...). Thus, we're a little behind, so this is more of a The-Past-Two-or-Three-Weeks update.

So, The Past-Two-or-Three-Weeksly tally:
- 120 bones measured out between Oct 10 - 24

notable finds:
- the coracoid of a Teratornis merriami (Merriam's teratorn). Teratorn's were huge birds of prey; their name means "monster bird" in Greek; they had a 13' wingspan; and they looked kind of like gigantic condor-vulture hybrids.
- the radius of a Capromeryx (dwarf pronghorn)
- again, a whole grip of ribs from a whole bunch of animals, all laying on top of each other. Excavating them has been like playing pick-up sticks in a graveyard, but we finally got at least a dozen out of the way, including three complete vertebral (as opposed to sternal) ribs.
- several Giant Ground Sloth caudal (tail) vertebrae and haemal arches (mini-psuedo-vertebrae that articulate with the underside of caudal verterbae)
- the semi-complete underside of a turtle shell. This was found in a section of the deposit that we previously thought was sterile, which is very, very good news -- more bones means less boring fossil-less dirt to dig through.
- Dogs and cats are peacefully co-habitating in grid B-1; we've found 3 dire wolf skulls so far (2 are pictured below), various bones from at least 2 coyotes, various bones from at least 2 saber-toothed cats, and as Ryan previously posted, the skull of a North American lion has been uncovered, but not yet excavated.

Grid B-1, Level 2, as of October 24, 2008

One of the dire wolf skulls (from a particularly old individual -- his teeth are worn down almost to the root) is directly on top of the lion skull.

highlight of the north american lion skull. mouse-over for the highlight of the dire wolf (if the image doesn't immediately shift, wait a few moments for it to load, and try again).

- as I previously posted, the saber of a saber-toothed kitten has been exposed.


As you can see, saber-toothed cats were born with little sabers, which makes one particularly pity the saber-toothed mothers...

notable events:
- After months of excavation, Kristen got the giant ground sloth scapulas out!!

and grid B-2 has gone from this:

to this:

That's a giant ground sloth ulna in the center. Eventually, I hope to plot the location of all sloth bones in Deposit 1 to get a better idea of how, exactly, the animal's skeleton fell apart.

Once again: progress!

18 October 2008


we found two saber-toothed KITTEN sabers! completely amazing. pictures forthcoming. wait, with bated breath, you shall....

16 October 2008

Note from the Lone Male Excavator:

I have often been asked what it is like to work as the lone man among four women. I usually reply in one of two ways. On a good day I say, "It is awesome to work with four talented, intelligent, beautiful, tough women." On a day when I am forced to watch The View and/or Oprah during break times I say, "There are good days and bad days." In essence each of my responses is true, but overall, I work with four people that know, as I do, that we have one of the coolest jobs on Earth. Though our tight-knit group is a socially intense and complex small band of hominins, it is this author's opinion that intragroup cooperation is facilitated quite readily by the composition of individuals and the male to female ratio.

Now, I'm sure you've heard enough on that matter for this post, and even if you have not, too bad, because I have something far more interesting to discuss:
We have partially uncovered the skull of a North American "Lion" (Panthera atrox). I'm sure that pictures will be posted of this find as we make more progress in removing the bones still above it and, finaly the skull itself. From what we have seen so far it is at least fairly well preserved. As was noted in an earlier post, we have also found a P. atrox pelvis. The skull was found in the same grid only a few inches below. We are curious as to how many of the many ribs and vertebrae and other bones found in this grid might also be attributable to P. atrox. Many of the bones in this grid have been of Smilodon [including a complete saber (upper canine)] and it is not always easy to determine an identification of the more general bones until they have been cleaned in the lab.

Well (2!), until next time...

15 October 2008

measure for measure

Earlier this week, we measured out the left half of an American Lion pelvis (or, more anatomically correctly, an innominate). Whilst typing this into yesterday's entry, I realized I've never actually explained what "measuring" a fossil entails, let alone why we do it.

"Measuring out" a fossil means recording the location of two to three of the bone's anatomical points (usually three) within the context of a 1m x 1m x 25cm grid. For instance, take our most recent innominate:

The three dots and abbreviations above represent the three different anatomical points: IC stands for Illiac Crest; PT means Pubic Tubercle, and DP means Dorsal Posterior (which isn't actually a point -- it's a general orientation. This portion of the bone is broken off, so there isn't an actual feature to measure. Instead, we measure an arbitrary point, and name it after the point's location in the body: Dorsal, or toward the spine, and Posterior, or toward the rear end).

Each of these three points gets three pieces of data of their very own: measurements of the fossil's location below the original surface of the deposit (abbreviated as "BD" for "Below Datum"), north of the southern most line of the grid (N), and west of the easternmost line of the grid (W). These measurements are written into our field notes, and carbon copied (literally, with little blue pieces of carbon paper) onto 3" x 5" cards. Confused yet? Fear not, it sounds much more complicated than it actually is. But here's an enhanced version of the final product:

Remember Algebra class waaaay back in 9th grade? Wait, let me rephrase that -- remember any of the math from Algebra class waaaay back in 9th grade? Yeah, me neither. However, had you paid closer attention to the graphing portion of your text (and less attention to Spitball Trajectory 101), you would recognize those three columns of numbers as coordinates within a 3-dimensional graph. For example, for the IC, x = 43, y = 42, z = 32.5, etc. By recording all of these coordinates, we're able to later reconstruct the fossil's position within the deposit. And in doing that, we can learn all sorts of nifty things about how skeletons fall apart within a tar pit, or which animal got trapped first, or how asphaltic sand shifts underground over time, and so on and so forth.

A better photo narrative of a fossil's journey from grubby, dirt-covered groundling to a finished, fully prepared specimen is forthcoming, but until then, I hope this has been helpful. Or, at the very least, has inspired you all to pay closer attention in Algebra II.

14 October 2008

this week in urban paleontology

Busy, busy excavators we have been!

The photo above shows the 50+ fossils we've measured out over the last two weeks. Extremely note-worthy finds include:
- a metacarpal (hand bone) of a Capromeryx (an extinct and fairly rare species of dwarf pronghorn)
- numerous saber-toothed cat and dire wolf ribs
- at least 6 sub-adult thoracic vertebrae (vertebrae from the rib cage) of a saber-toothed cat. We think they're all from the same individual animal! They were all found in the same 50cm X 50cm x 25cm area of the fossil deposit, and all appear to be about the same age. This is the sort of semi-articulation or association that we've been so excited about finding, because we very rarely (if ever) find it in Pit 91.
- part of a dire wolf skull
- at least four coyote jaw pieces
- a sloth sternal rib (a rib from the front of the ribcage, rather than the back. If you can't find one in your own torso, don't worry -- humans do not have sternal ribs. If you do find one in your own ribcage, please let us know! We'd be extremely interested in studying you...)
- the astragalus (an ankle bone, AKA the talus in humans), scapula, and pelvis (pictured below) of an American Lion

the measured pelvis, in it's natural environment: a metal bucket and a plastic bag. more on this tomorrow

What does this mean? Well, we've found not just one, but TWO of Rancho La Brea's rarer species (the American Lion and the Dwarf Pronghorn) in our first month of digging, not to mention another unique instance of fossil association! This first deposit is already adding to our knowledge base, and these discoveries bode well for the rest our excavation.

And remember this?

(l to r: sloth left scapula, sloth right scapula, ryan)

it now looks like this:

(l to r: dustpan, sloth left scapula, yet another tibia, sloth rib, sloth right scapula, michelle)