16 November 2009

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.

17 October 2009

update: out of 7A, back in to deposit 1

they escaped from the tar pits, but not from each other: these two dragonflies were
found flying around together, attached at the hip by asphalt. Michelle kindly helped
free them. From 7A and back into 1

Right. So we've been working steadily in deposit 7A, and are about 1/2 a meter down in all areas. There were three bones immediately visible on the surface (all sliced by the tractor that found them, and horribly dried out), but other than that we've yet to find any substantial vertebrate fossil deposit. We've found a few scattered pieces of turtle shell (not to mention some extremely odd fragments of mineralized bone -- very rare for Rancho la Brea!) but none of the big jumbly bone masses we've come to know and love. What we have found:

Shells shells shells! From 7A and back into 1
Gastropods! And lots of them.

excavator hand for scale, From 7A and back into 1

These freshwater snail shells are further contextualized by the immense amount of plant material we've been getting out of the deposit as well; the northeastern corner of the deposit is filled with what appear to be tree branches (but possibly roots). Additionally, there's some interesting stratigraphy going on in this deposit: layers of river sand and large rounded rocks.

But as of yet no big vertebrate fossils. Boo.

For that reason (and because we're acutely aware we're already one year into a five year project!), we've put deposit 7A on hold, and re-doubled our efforts in deposit 1 (the big box we first started in).

That's usin' your head, Russ. From 7A and back into 1

And we've made some really impressive progress! But more on that next post. Until then, I leave you with this month's "What is it?" Check out the photo below, and leave a comment with your guess of species and element! Correct guesses win a congratulatory shout out on the next post, and the knowledge that they have bettered their internet peers!

I'll give you a hint: it's a fossil. From What is it?
Happy guessing!

01 October 2009

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!

04 September 2009


This is The Ghost of the Lone Male Excavator! I just wanted to drop in and announce that I have nothing paleontological to report. Also, I await the next blog post from Andrea ...rattle, rattle, rattle...

28 July 2009

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

dainty dainty dainty
ping ping ping!

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

meena angry, meena smash!
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:

7b as it was... and never shall be again.

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:

zed's femur

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

That's it for now, more later!

21 July 2009

may the force be with ryan

ryan's favorite outfit

Sad but true: our Lone Male Excavator has left us for more exotic locales (grad school in plant and soil sciences on OAHU) and we miss him already. Ryan has been a careful and conscientious excavator, a funny dude, a good friend, and last but not least, an incredibly snazzy dresser (plaid + camo = AWESOME).

Yes, we will miss his hard work, his dedication to replacing shoring boards in the heat of summer, and his enviable ability to reach things on tall shelves, but we will also miss his encyclopedic knowledge of all things Star Wars, his willingness to talk in funny voices for our amusement, and perhaps most of all...

ryan's chair

his unparalleled ability to re-purpose old broken office furniture during his lunch break. The above photo may appear to be an ordinary office chair, but look closer! It is actually an office chair attached to another chair because it broke off its original base. The wooden legs of the base chair have been careful sawed at an angle for maximum comfort.

And what became of the base of the chair, you ask? BEHOLD:

ryan's sidetable

This is quite possibly my favorite piece of furniture ever. It's an end table! On WHEELS! This handcrafted beauty is made of another chair (with the back sawed off) screwed onto the base of the broken office chair, with a piece of laminate for a top. And it's the perfect height for chips and salsa!

Finally, Ryan's coup de grace:

ryan's desk

A genuinely well-made desk for volunteer Christina, made out of the side of box 10B (I think it's 10B).

In conclusion: Ryan is awesome! We totally miss him! He is funny and us taught about plants and how to sharpen tools and such! However, on the bright side: we now have a couch to sleep on when we go to Oahu...

Godspeed, Ryan

Godspeed, Ryan, and may the force be with you.

14 July 2009

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.)

08 July 2009

a small but big discovery

Hello! We found a very neat thing a few weeks ago:

Associated bird skeleton in situ at the La Brea Tar Pits

It's a bird! It's a plane! It's-- wait, nope, it's a bird. The many small bones in the upper left-hand corner (with the big arrow pointing at them labeled "bird") are all from a small passerine, (or "perching bird"). These bones likely represent an associated individual; they were found in a slightly separate layer of asphaltic sand than the rest of the deposit, and some bones even appear to be somewhat articulated. In other words: this is the almost complete skeleton of a small bird; this is extremely rare; I have named him Kevin.

Though most birds are passerines, they are nevertheless rare at Rancho La Brea; our collections are dominated by bigger birds of prey like teratorns and condors. It's hard to say what species Kevin is, exactly -- especially without cleaning and preparing the bones first -- but Lab Supervisor Shelley says he's about the size of a scrubjay.

Kevin the associated bird from Project 23 at the La Brea Tar Pits

The bones in the numbered in this photo are as follows:

  1. carpometacarpus
  2. scapula
  3. 2 limb bones -- not sure which exactly
  4. sternum
  5. tibiotarsus? I think?
  6. tarsometatarsus
  7. femur?
The photo above was taken after removing a number of other bones separately, such as ...

furculum of small bird (kevin)
the furculum...

scapula of small bird (kevin)
another scapula...

A passerine humerus, with finger for scale

...and a humerus (as well as an articulated synsacrum and femur, several vertebrae, and several phalanges that I don't currently have photos for). After removing these uppermost bones and discovering there were even more underneath we decided to remove the rest of the skeleton in one block...

Associated bird skeleton about to be removed

which was accomplished by gently prying the layer of asphaltic sand it was rested in with well-placed screwdrivers and chisels.

Though this skeleton is exciting in and of itself, its context may actually be more important. As regular blog readers may remember, up until now Deposit 1 has been more dirt than fossils. There's a dense cluster of bones in the southeast corner that has yielded at least 1000 specimens (and at least that many more to come), but about 3/4ths of the box has been largely sterile. Not anymore. As we dig deeper into the so-called "sterile" areas, we've found a new layer of fossils:

where kevin was found.

This is a different style of deposition than in the "main" bone cluster we've previously worked on:
  1. These fossils are spaced further apart, and spread out more evenly -- not all jumbled together like pick-up-sticks.
  2. These bones are broken, weathered, and worn. The bones in the other cluster are largely complete
  3. Many of the longer bones and bone fragments point in the same direction (scroll back up to the top of the page to get a closer look) -- perhaps implying stream movement? We don't know! But it's interesting...
Kevin was found in the northwest corner of this grid (near where the meter sticks cross) in a slightly separate layer of asphaltic sand -- perhaps implying that he flew in and got stuck after the rest of these unlucky beasts? Again -- we don't know! But also interesting! We will keep you posted as things and finds progress.

09 June 2009

update update update wow.

la brea tar pits panorama - pit 91 compound

OH, we have been bad bloggers. Apologies for the complete and total lack of communication. BUT, in our defense, we've been really busy. Look:

Project 23 @ the La Brea Tar Pits - box 7B

This is Deposit 7B, and it is open for excavation. Now that 10A and 10B are done, lead excavatrix Kristen and curatorial assistant Aisling decided that the 7's would be next to go (while continuing work on the never-ending saga that is Deposit 1). According to APRMI's field notes and photos, the 7's are pretty fossiliferous -- more so than 10A and 10B, anyway -- and so far, the sediment hasn't been terribly hard -- good for excavators' hands, good for the fossils' relative safety.

Serendipitously enough: Shelley et al in the lab just opened another plaster jacket in the lab labeled "mammoth" only to find that it's actually half of a Giant Ground Sloth pelvis from near Deposit 7. Other finds from 7B:

Project 23 @ the La Brea Tar Pits - box 7B

From top to bottom: the ischium of a bison pelvis, an herbivore (possibly bison) rib, a cervical vertebra from a sabertoothed cat, a bit of plant, and a dire wolf humerus. We've also recovered another sabertoothed cat vertebra, another herbivore (possibly bison) rib, and a small piece of maxilla that may belong to a small dog or a mustelid of some sort -- we won't know until it's clean.

So, why has this taken up so much time? Well, I'll tell you:
Diagram of box 7B
Opening a new box/deposit isn't as simple as lifting up a tarp and digging in. First, we have to determine the box's original cardinal orientation -- that is, we have to figure out what side of the box originally faced north. More often than not, our imaginary north arrow isn't actually perpendicular to the northernmost side of the box; it's at an angle that can only be determined by carefully referencing original field notes from the salvage. It's only after we figure that out that we can set our grid lines, and begin digging. The diagram above (mid-pass from me to Laura) is a sketch of the overall layout of Deposit 7B, with every grid labeled, and the angle of that imaginary north arrow recorded for future reference. Did all that makes sense? If not -- comment, and I'll explain better next post.

So what else have we been doing?

The Page Museum hosted an Art + Science event in conjunction with LACMA's art walk. I put this 4 minute time lapse film-lette together for it -- PLEASE watch it; I think it turned out quite nicely! Time lapse experiments are largely responsible for stealing the time I would ordinarily spend updating the blog -- sorry! -- but I hope you will agree that the results have been worthwhile.

LACMA's art walk invaded our side of the park in a pleasantly chaotic sort of way:


These partially constructed hexagons of what would have been a geodesic dome spotted the hill surrounding the museum.

Bert the bear -- LACMA's art walk

And these white and black tarps surrounded our sloth and bear sculptures! By the end of the day, they were re-purposed somewhat...


...as awesome space age forts for young paleontologists. More pictures, as always, if you click on the picture above and explore our flickr photo feed.

Speaking of social networking...

...especially when I'm MIA, or if more than 140 characters is just too much for you.

Finally, Michelle has recently discovered her true calling: she is a poet, and she didn't know it. Her specialty: the ancient Japanese form of poetry known as the haiku:
Working in Box 1
Ouch! I hit my hand again!
Chiseling is hard.

Dermal ossicles
There are many in this grid.
Natural defense

Haikus can be so random.
Cheese quesadilla

Like I said, we've been very busy! Next update will be prompter, I promise!