update: more sabertoothed cats and kittens

Solar flares over our pulley. From Back in Dep 1

As I reported last post, we've moved back into the big box: Deposit 1!! And look how excited everyone is:

Volunteers Christina Lutz and Tara Thara. From Back in Dep 1

Those are the smiles of happy fossil finders. Why? Because they're actually finding fossils again! Between mostly planty deposit 7A, and really hard and sterile parts of deposit 1, we're been spending entirely too much time digging up dirt rather than fossils. Dirt = not fun. Fossils = awesome. It's very simple.

I've posted many, many pictures of this bone bed before (it's where we found our North American Lion skull and assorted long bones). And it's once again producing some really great feline finds:

Sabertoothed cat skull! From Back in Dep 1

The big dusty skull-looking thing on the bottom is a... big, dusty sabertoothed cat skull, with a complete sabertoothed cat pelvis immediately above it. And look a little above the skull and to the right:

Smilodon saber in situ. From Back in Dep 1

It's a complete sabertoothed cat saber!

Smilodon saber in one piece! From Back in Dep 1

And in the grid directly across from this one, we found 2 more sabertoothed cat kitten sabers:

Volunteer Steven Wintergerst holding a Smilodon kitten saber From Back in Dep 1

This may bring our (estimated) minimum number of sabertoothed cats in this deposit to around 7: 3-4 juveniles, 1 sub-adult (teenager) and at least 2 adults (I will have to double check these number with the lab). It's actually possible to match sabers to skulls, by taking casts of the alveolus (tooth socket) and comparing the cast to the tooth! This is something we might want to do in the distant future; because this deposit is so small we may be better able to discern which bones belong to which individual cat -- especially for these 4 "kittens" we've found. Yes, they're all young, but they're not of the exact same age (which makes me think this isn't a singular litter that got stuck). So by determining the age of each young sabertoothed cat bone we find, we can figure out whose limbs are whose, and then perhaps extrapolate from that how much the asphalt has moved/disturbed the skeletons since they first got stuck 10-40 thousand years ago.

In non-mammalian news:

Turtle shell! From Back in Dep 1

2 partial turtle shells have come out of the formerly sterile areas west of the main bone deposit. Turtle shells are made out of a number of interlocking plates, and while the individual plates are extremely common, articulated/associated ones are not -- in fact, these may be the only even semi-complete shells we've ever found at Rancho La Brea. Trevor's been working on them in the lab, and has one of them somewhat reconstructed (which he will hopefully tell you all about at some later date if he ever gets around to making a blog post, hint hint).

FINALLY two other items of business:

1) This is Carrie!

New excavator Carrie Howard! From Back in Dep 1

She works here now! She likes rocks and photography and is generally great.

2) I don't often share links on here, but for those who are interested in science education in America and the general fight to keep evolutionary biology from being grievously misunderstood may find http://www.dontdissdarwin.com/ helpful.

Next post: so, what's in that barn-looking building next to the trailer?

Greg A. hunts for lunch by Pit 10 From Back in Dep 1

No, it is not dinosaur! It is a degreaser, which is far more useful and hopefully far less dangerous! More later.

what we did over our summer vacation:

The scarab beetle in our compost pile says hello From End of 7B, Beginning of 7A

Well, not a vacation from digging -- just a vacation from blogging. Apologies to all, and regular updates will commence henceforth. SO:

Nola hammers the lid on the last matrix bucket from deposit 7B From End of 7B, Beginning of 7A

We finished excavating deposit 7B in early August. Final tally of things found is still pending, but all in all, it was rather pleasantly fossiliferous. Some of the cooler finds include a number of potentially associated bison bones (the bison itself has been named James K. Polk), a mostly complete sabertoothed cat skull (named Bixby) (I will have to explain our naming conventions in a later post...), several unusually large sabertoothed cat limb bones that might belong to Bixby, several rattlesnake vertebrae, a gopher skull, the usual slew of dire wolf bones, and lots and lots of tree branches (tentatively ID'd as manzanita). And nicely enough, 7B continued to produce bones down to its final few layers:

Sabertoothed cat cervical vertebra From End of 7B, Beginning of 7A

This sabertoothed cat vertebra was found at the very bottom of the deposit. As you can see, the right-hand side of the vert was sheared off in the process of putting a bottom on the box -- no good! Ah well -- such is paleo-salvage. Of the 327 buckets recovered from the LACMA site, a substantial number were labeled "Deposit 7." Someday (hopefully sooner rather than later), we will degrease the buckets and try to find this vertebra's missing half, but for now, we best be moving on...

Deposit 7A From End of 7B, Beginning of 7A

...to deposit 7A! 7A's a bit bigger than 7B, so we built this nifty railing to keep us from plummeting to our deaths (or, more likely, tumbling to a sprained ankle, but whatever, SAFETY FIRST dang it), and we've got some strategically placed Little Giant ladders around to help us in and out. But check out that silver thing on the side:

it's like a slide for matrix! wheee! From End of 7B, Beginning of 7A

Rather than breaking our backs hauling buckets in and out of the box, Michelle came up with the great idea of leaving the buckets on the ground, and using a make-shift funnel to pour the matrix in. GENIUS! And I can't believe we didn't think of it earlier. It's not about working harder -- it's about working smarter.

After finding deposit 7B fossiliferous to the very end, we had high hopes for 7A, but were (understandably, I think) a bit disappointed to find only this dehydrated mess greeting us on the deposit's surface:

that chalky stuff in the center is bone. ugh. From End of 7B, Beginning of 7A

Blech. Nevertheless, we soldier on! We've been working on Deposit 7A for about 2 months now, and we have found a few specimens, here and there...

Laura finds a specimen here, a specimen there... From End of 7B, Beginning of 7A

...but more on that next post, which I promise will be next week (I don't want to overwhelm you after my long absence). Cheers!

With Ryan gone, life is much daintier here at Rancho La Brea.

ping ping ping!

However, this does not mean that we are not still capable of great feats of strength:

once, this was a chisel. now, it is rubble. such is life.

as is evidenced by the still-growing pile of broken tools left in our wake (volunteer Meena broke this one...)

Thus, over the last week our girlie muscles have brought Deposit 7B down almost a meter below its original grade. 7B is small, and not densely fossiliferous, but nevertheless productive enough to stay interesting:

The femur is the latest of several sabertoothed cat bones we've excavated from this area (including a skull!), and we're wondering if they're all from the same individual animal. We won't know for sure until they're cleaned and officially identified by the folks in the lab.

Less immediately exciting, but still important: there's a huge chunk of rock hard oxidized asphalt right in the middle of the deposit. There are bones around this asphalt, but not in it. We think this might be a vent -- the fissure in the ground that the asphalt originally oozed up from! We've seen this in Pit 91 before, but haven't been able to observe it as well as now. We only worked in Pit 91 for 12 weeks out of the year, and would only excavate a fraction of the exposed grids each season. This means that though interesting geological features were documented, it would sometimes take years to see if they continued another foot below the surface -- just because it took us that long to excavate the entire floor. Working year round with smaller deposits is allowing us to focus on unexpected geologic/taphonomic environments like this one.

I mentioned the lab earlier, and soon we'll have a proper Update From Indoors but until then:



here's a soundtrack-less time lapse of the preparation of Zed's right femur. Still a work in progress, but you get the general idea. Email subscribers: visit excavatrix.blogspot.com to see the video. Or scroll down:



to see Zed's femur in it's shiny, well polished glory.

That's it for now, more later!

Final Note From the Lone Male Excavator

Shore, -ing. (Verb):

the process of replacing old side-wall boards in large dug-out spaces (e.g., Pit 91).

This post will serve as both an introduction to some of the "other work" that excavators (and excavatrices) perform at Rancho La Brea and a documentation of the particular method of shoring board replacement that the Lone Male Excavator has developed.

So as the thick boards holding up the side walls of Pit 91 grow old, they often bow out, rot out, or both. Up above the pit, 14ft x 11 3/4" x 2 3/4" boards are stored ready to be cut to an average of about 75" long for use as a shoring board.

After a board is slated for replacement, of course it must be extracted. This is commonly far more difficult than it sounds. If the board is rotted to extremes on the ends locked in by the I-beams, then it is not too tough for a hatchet to cut through one end and pry the board out with a crowbar. If the board is not rotted away much at the ends, however, (as the boards pictured here) it can be quite difficult.

Initially, a cut with a circular saw is made through the board(s) being replaced. This is very dangerous and every safety precaution must be taken at this point (e.g., clean goggles, steady hands, hard hat). It is also messy and anything, including one self, which should not get covered in sawdust should be protected. If two parallel cuts, about 2" apart are made, extraction will be easier. Our cordless circular saw, however, does not cut deep enough to go through to the back of the boards.
So I have added to this method inspired by the wisdom of William A. Akersten's thought on sabertooth cat incisor (front teeth) functional morphology.

The points on large, cone-shaped incisors of Smilodon fatalis are separated to the extent that when they pinch together top to bottom and pierce into the skin of prey, they are thought to create a perforated line which allows for easy tearing off of chunks of flesh. When we are unable to pry/break out a board along the saw cuts, holes can be drilled along the cuts to create such perforated lines which can then be hacked trough easily or broken out through prying.Once a board is out, the wall of earth, often asphalt saturated, must be shaved a little with hand tools or, in dire need, a pneumatic chipper. Occasionally fossils are found in the side walls, so these must be watched for and documented when discovered.

Depending on the thickness of the new board and the bowing out of the old board shaving the walls may take up to a couple hours. Once this is done a measurement for the new board's length is taken, giving about an inch and a half behind the lip of each I-beam. (Often, when you think you've shaved enough and try to get the new board in, you find that a few spots need more shaving. The first of these two pictured here took me 3 attempts. I also found that I had cut it too long and had to take an inch off one end.)

After you've seen that the board will fit the space you've shaved out of the earth-wall, you must get it equally situated behind the lip of each I-beam... not so hard when you've got two-three boards out and you are doing the bottom board, but if you are trying to slide a single board over in a single space (like w/ the second board pictured) it can sometimes involve a long trial messing with crowbars. I have no solution, except putting in the lag screws early and trying to use them to slide the board. This does not often work.

If gaps are left, they are reduced by placing thin pieces of wood at the bottom of boards.

The boards are locked in between (and behind the lip of) I-beams which run about 40 ft under ground. As much of the board as possible is slid behind the inside of the I-beam before 5/16" holes are drilled beside the lip of the I-beam for 9/16" x 3 3/4" lag screws. The lag screws go through, what I'm gonna call, giant square washers which tighten the board flush to the I-beam. A thin, small piece of plywood is often needed between the shoring board and the giant square washer.

There you have it; Shoring 101. The final exam is getting a board replaced and not injuring yourself in the process.

So the Lone Male Excavator is off to grad school. This is my last day as an excavator at the Page Museum at Rancho La Brea, but I will still be around in spirit. (In fact don't be too surprised to see posts in the future by The Ghost of the Lone Male Excavator.)

update: the demise of deposit 10a, the flattening of deposit 1

After about 8 months of digging, Deposit 1 is finally starting to look markedly different than it did when we first unveiled it -- well, to us, at least. Yes, it's still a dusty hunk of rock, but now it's a dusty hunk of rock that's around half a meter shorter than when we first got it.

As I've hopefully mentioned before, we work in 1m x 1m grids, and dig down 25 cm at a time. You've seen this before:

...the large, convoluted bone mass that was keeping us from "closing" grids B-1 and B-2 and moving on to other portions of the box. In both grids, we're working on level 3, which is the section of dirt 50-75 cm below the original ground level of the deposit. Does that make sense? Those large saber-toothed cat scapulae and innominates were sticking out above floor (the bottom of each 25 cm deep level) and needed to be removed before moving on.


Now the grids look like this:

Yes, there are still bones, but if you look carefully, you'll note a wonderful lack of scapulae...

...because Tara got the last one out! Everything left in place is too far below floor to excavate at this time. The grids surrounding the bone mass are still at level 2, so we have to get those down to level 3 before we can open up grids b-1 and b-2 at level 4. Did that all make sense? Excavational peccadilloes are difficult to describe via the interwebs. To sum up: if we keep excavating just the main bone deposit, we'll wind up with a giant hole in the ground (in the box) which will be too deep to keep digging at. So: sterile grids for us, for a while.

In non deposit 1 news: as Ryan and I have both mentioned, 10A is no more! We time lapsed it's final moments:

I have to say, I like the soundtrack to this one better than last week's, but I don't think anything will match excavation to the tune of "I Am the Walrus." Ah well.

Next week: we just laid grid lines out for 5 new deposits -- 7A-E! We're very excited to start work in new, softer dirt. Pictures soon to follow. OH! And click through to flickr to check out the giant freaky black (and brown) widows Laura and Michelle found under 10A.

more fun with time lapse

We've been having a lot of fun with the built-in intervalometer on our new camera:

expect more videos like this in weeks to come! To our email subscribers -- the blank space you see above (and in my last post) is actually a youtube video embedded in the blogpost, which unfortunately doesn't seem to translate to email. Go to excavatrix.blogspot.com to view.

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:

VERITABLE, I say!

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!

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!

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)

Progress!

update!

Long time, no update, but with good reason: we finally officially "opened" our first fossiliferous grid in our first fossil box from Project 23, and we've been too busy digging to blog. Hopefully, some pictures will make up for the thousand or so words we have not written.

Below, a view of B-1 circa a few weeks ago:

roll-over for highlight

The three highlighted bones above are all tibias, and are all from the right leg. However, they're from three separate animals:

From left to right, you're looking at lower right hind leg bones of a coyote, a dire wolf, and a young saber-toothed cat.

We finally got the saber-toothed cat pelvis off the top of the grid:

Note the pelvis-shaped impression in the ground to the left.

Volunteer-of-the-Century Harry made us a brand new tool box:

which now holds our brand new phone, our brand new field notebooks, our brand new meter sticks, our really-old-but-still-totally-useful comparative collection of dire wolf and saber-toothed cat carpals and tarsals (wrist and ankle bones), and, apparently, my three-hour-old cup of coffee.

And speaking of volunteers, we've started bringing them up to help us dig! Tara-the-ever-persistent, of course, was our first:

And finally, we put together a small exhibit for the museum explaining how Project 23 came to be:

The two ribs on the left of the case are from our semi-articulated mammoth; the rib on top is normal, but the rib on the bottom has a large bump in the middle from a break that healed during the mammoth's lifetime. Zed (as the mammoth has been dubbed by lab supervisor Shelley Cox) has several broken-and-re-healed ribs on his right side; he must have sustained a massive injury which he subsequently recovered rather nicely from. And the fossil block on the right is the same block of skulls that came from the "blob" we wrote about last month. The brown vertebra in the middle is from Zed; the white vertebra above it is from Jenny:

Shelley borrowed an Asian elephant skeleton from the Natural History Museum and has been using it to help identify Zed's (much larger, but still comparable) elements. In the photo above, Shelley is comparing Zed's ribs to Jenny's (Zed's are La Brea brown; Jenny's are white).

More soon!