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Showing posts with label bird. Show all posts
Showing posts with label bird. Show all posts

15 August 2010

Introducing Box 14

Excavation of deposit 14 has been underway for almost 2 months now and has been very fruitful, as expected, due to what we have already seen in the amount of spill-over fossils that were put in buckets when the deposit was removed from the ground, as demonstrated here by Andie in a previous blog. But before we could poke our dental picks in the top asphaltic sugar sand already showing signs of large bone we had to transform the highly awkward box into something we could work with.

This is how it came to us, after protective tarp removed

box 14 uncovered

The actual deposit is the darker colored sediment in the center. It fell apart when they were trying to excavate it and came to us wrapped with a few boards and metal bands, then plastic, and then supported by tons of the sterile "fill" dirt within the space of the tall box.

box 14 surface

Box excavation preparation included cutting the metal bands that crossed over the top of the box, assembling scaffolding, removing front top board so the public can see us work, affixing handrails for easier boarding, setting up a shade canopy, and determining grid lines, and then box 14 was ready for digging!

box 14 scaffolding

The fossiliferous asphaltic sugar sand midsection of the deposit is relatively easy to dig in. It softly peels and crumbles away from the bone. We never have it completely easy though, as within it there are also spots of hard oxidized asphalt as well as bones that have already been fractured. Given that the deposit was disturbed upon excavation we also have not been taking three point orientation measurements of bones as they are believed to be disrupted from their original position. The only data thus far taken has been the grid and level that the fossil is found in.

Included in what we have found so far:

  • 2 large hervibore vertebrae including sloth
  • 1 coyote skull
  • 1 dire wolf skull, tibia, radius
  • 2 juvenile saber-toothed cat mandibles
  • lots of bird - including golden eagle skull, teratorn sized limb bones, male
    turkey, and hawk
  • "lots of turtle" - according to Trevor there are at least 3 individuals
  • pieces of juvenile mastodon skull including a maxilla with teeth that
    indicate its young age, possibly younger than any mastodon in the RLB
    collection, along with a tibia

    Meet "Snuffleupagus" or "Dumbo"

    field photo
    juvenile mastodon field photo

    after some cleaning by Henry
    IMGP7077

    Also, here's an example of what the main fossil deposit in 14 looks like
    box 14 grid C3/L2

    and the bird beak I found (my first), which is eagle sized
    beak

    and the perfect furcula from a medium sized hawk that Michelle found


    Deposit 14 has been worked down two levels and in order to continue we
    have started removing fill dirt so that we can remain excavating from the deposit's side. Last week bucket by bucket we removed over a ton of fill. Literally. Thank you Sunday volunteers Karin Rice, Bruce Fischer, and Katelynn Simpson for being awesome dirt movers!

    Now this is 14's current look
    deposit 14 at level 2 floor

    In other P23 news the reopening of the rather non-fossiliferous deposit 7a has yielded 3 horse cervical vertebrae and progress has been excellent in box 1. More updates are to come!!!

    • 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.

    13 January 2009

    update

    happy christmas
    happy non-denominational seasons greetings and new year

    It is 85 degrees Fahrenheit in Los Angeles right now. In January. In what is supposed to be the dead of winter. We are mildly confused, but not complaining; digging in asphalt is so much easier in the warm sun! The matrix in two particular grids -- A-1 and A-2 -- has been soft enough to dig through using our fingers. Findings of note:

    lynx mandible

    This jaw is from a small wildcat, most likely a Lynx, per collections manager Christopher Shaw. We don't have that many bones from smaller cats in our collection at the Page Museum for two reasons: 1) these smaller cats were likely solitary, so when they got stuck in an asphalt seep, they got stuck alone -- not with 15 of their closest friends, as with Dire Wolves and Saber-toothed Cats. 2) smaller cats have small bones, and early fossil collectors (during the early 1900s) would have likely passed them over for larger, more obviously interesting fossils like, again, those of the Saber-toothed Cat. This is what's called a collection bias: the arbitrary favoring of one kind of fossil or specimen over another. One of the main goals of the excavation in Pit 91 and with Project 23 is to correct this bias. Thus, we collect and keep everything -- even the stuff that might not seem obviously important at the time. For instance:


    fossil assemblage, grid a-1/level 3

    In grid A-2/Level 3 I found two bird tibiotarsi (i.e. drumsticks) immediately on top of one another. They're definitely from the same species (but I don't know which one), one tibiotarsus was a left and the other was a right, and they are about the same size. This may be a case of association (two fossils from the same individual animal), or it may be just a really weird coincidence. But it kind of doesn't matter: it's an unusual enough case to warrant thorough documentation. Pictures, notes, and measurements have been taken, and preserved for posterity. I am but a lowly excavatrix -- not a proper paleontologist -- and I haven't the years of schooling necessary to interpret this assemblage. But good data collection will hopefully benefit actual paleontologists of the future, as they dive through field notes and make the interpretations that we excavators couldn't. Ryan, our sole man, noted the following:

    pleistocene oak leaf

    The orange bits are a complete oak leaf found from a largely sterile portion of Deposit 1. We've found a large number of plant parts, and a good number of oak leaves in this deposit. We don't know what plant is worth collecting and what isn't, so we try to collect as much as possible. Again, this is something for future scientists to interpret. And it's our job to make sure everything's collected in as complete a manner as possible. Finally, an eagle-eyed volunteer (hi Spencer) spotted the following:

    some interesting dirt

    a pile of orange dirt. While this wouldn't be surprising in any other fossil deposit, anything with any hint of color at the La Brea Tar Pits is worth noting. So a sample was collected, notes were taken, and hopefully this will give us some insight into the depositional environment around this particular deposit.

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