update: PROGRESS

Remember this?

Flip it upside down, replace employee Michelle with volunteer Christina, add in a heat gun, and you get THIS:

That, paleo-friends, is the skull of a North American Lion -- Panthera atrox. We finally finished removing all the bones around it, and thus successfully excavated the skull!

But first, here are some interesting inferences about North American Lions, provided by our fair leader, collections manager Christopher A Shaw:

- North American Lions showed up in their eponymous continent (North America) around 400k years ago

- They were probably not social animals -- in other words, there were no prides of these particular lions. We think this for two reasons:

1. We don't find nearly as many of them as we do dire wolves and sabertooth cats, and not with nearly the same range of ontogenetic age. For example, we've found approximately 6 North American Lions in Pit 91, compared to around 50 Saber-toothed Cats.
2. In a pride of African lions, the ratio of males to females is 1:6 or 1:7. Here at Rancho La Brea the ratio is about 1:1. Thus: no African Lion-esque prides. North American Lions likely had a more solitary lifestyle, more akin to that of a mountain lion.

- These lions likely did not have manes. Cave drawings in North America exclusively feature mane-less lions -- either that, or only females, which doesn't seem very likely.


Back to our skull: after months of carefully using dental picks to clear out the surrounding matrix, we eventually had to resort to brute force to get the lion skull out.

That's me on the left, Michelle on the right. I'm rocking the skull back and forth on its side to loosen it from the surrounding matrix; Michelle is holding on to a bone underneath the skull to keep it from coming out along with the lion. Aisling wisely thought to film the entire process:

Background soundtrack provided by: Marketplace with Kai Ryssdal on NPR; Laura Tewksbury singing; various lab volunteers cheering; and me saying "there's a frickin humerus attached to it!" A great orator, I am not...

Though quality on this video isn't the best, it is good enough to show just how tough it is to get something out of an asphaltic deposit. Even after putting all of my weight behind the skull, at first it barely moves. However, after some artful wiggling (and a decent amount of luck) it's out!

And there was much rejoicing! Yes, I could have continued removing matrix with the heatgun and a dental pick until the skull basically fell out. However, the more you use a sharp pointy object near a priceless artifact, the more likely it is that you scratch aforementioned priceless artifact (or one of the other 20 priceless artifacts under the skull that you can't even see and will therefore probably put a hole into). Thus, every once in a great while, it's better to use your bare hands and just push.

The skull itself is an absolutely beautiful specimen; it's the most complete P. atrox skull we've gotten out of the current excavations (i.e. Pit 91 and Project 23).

Look at all those bones I could have damaged had I continued using a dental pick! The crescent shaped bone in the lion's mouth is a horse hoof; there's a complete saber cat rib in the back; and yes, on the right -- there's a fricken humerus attached to it. Sabertoothed cat humerus, to be exact.

And now that the skull's out, we can get on with our excavation.

These are just a few of the bones that are now accessible thanks to the skull's removal. Click the picture above to be taken to our flickr site, where you can mouse-over individual bones and find out what they are.

As for our skull...

Laura promptly carried it off to the lab, and rumor has it that Herb will begin cleaning it in a few weeks. We think we'll name it Fluffy.

update-ish

Too busy for a proper post, but if you click the photo above, you'll be taken to our flickr site, where I just uploaded about a dozen pictures from the filming of Dirty Jobs. More pictures next week, because friends, paleontology waits for no woman. We've had an extremely productive week, and just two short hours ago, we FINALLY got the North American Lion skull out of deposit 1. And let me tell you, it is a beaut. So once we're done basking in the glory of a job well done, we'll get back to blogging. Cheers!

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.

look!

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!

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...

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.