Glopping in Pit 91 today!
It's time to glop! We were back in Pit 91 last week to remove the continually seeping liquid asphalt.
It's time to glop! We were back in Pit 91 last week to remove the continually seeping liquid asphalt.
Work continues on in Box 14, and some of the bison bones in the center of the deposit are in process of removal. This image shows: a tibia (1) that was removed Saturday, a scapula (2) that is broken in place, and a left metacarpal (3) located below the scapula.
Fresh out of the ground in Box 14, and just in time for Thanksgiving, we found the upper part of a right tarsometatarsus (lower leg bone) of an extinct California turkey, Meleagris californicus. Only male turkeys have the spur that protrudes from the rear of this bone, making it a quick and easy way to identify the sex of the individual. Male turkeys use the spur in a kicking motion to help fend off predators.
Now that SVP is over, we are back to digging in Box 14. One significant discovery from the past couple days is this fragment of a juvenile horse mandible. We recovered another fragment of a very young horse mandible in Box 14 last January in an adjacent grid and it is most likely that they are from the same individual. So far in Box 14 we have juvenile representatives of mastodon, camel, dwarf pronghorn, dire wolf and horse.
We have been busy lately preparing for visitors to our museum from the Society of Vertebrate Paleontology's Annual Meeting that is happening next week in Los Angeles. Shown here, the Page Museum Research and Collections staff works on a new lineup of skulls in the lab, and volunteer Bethany glops in Pit 91.
The saber-toothed cat femur on the left is currently being excavated in Box 13. The damage to its surface is not from a scavenger but is called "pit wear." The large grooves on the surface of this bone formed when it moved against other bones within the asphalt seep. The cause of the movement is uncertain but could conceivably represent migration of the asphalt within the seep, trampling from other animals that were caught in the seep, or the result of earthquake activity.
This is an image of a section of millipede that was excavated in box 1 from hard asphaltic sandy matrix. Upon close inspection, some of its tiny legs are still attached to its body and may even be complete (see lower section of image).
These are some nice specimens that we have discovered in box 1 excavation recently:
2. plant and twig mass
3. impression of small beetle (top) and millipede (bottom)
4. beetle elytra with purple pigment, as seen when first exposed. The color fades in a few minutes when exposed to air.
This is one of many well preserved Pleistocene branches being cleaned in the Fishbowl Lab at the moment. The wood almost looks modern but was excavated from among bones that are ~35,000 years old.
Recently found while cleaning bulk matrix from deposit 1 in the lab, this is a dentary of a juvenile dwarf pronghorn, Capromeryx minor. It is probably the youngest pronghorn individual represented in our cataloged collection.
The paper, entitled "Paleoecological and taphonomic implications of insect-damaged Pleistocene vertebrate remains from Rancho La Brea, southern California," will be published in the journal PLoS One on July 3, 2013
After a month of digging in Box 13 we have almost completed one level (25cm) and it has continued to be a deposit packed with many fossils. The above image shows what we are working on this week.
We opened our 9th Project 23 box last week! This one is part of deposit 13 and is located on the east side of the compound, being shaded by our Page Museum canopy. Many large vertebrate fossils were exposed at its surface, including the back of a saber-toothed cat skull, a saber-toothed cat cervical vertebra, dire wolf teeth, large bird bones, and large herbivore long bone fragments and teeth. A condor-sized humerus and juvenile horse tibia are among what has so far been excavated. Box 13 is another deposit packed with well preserved fossils!
We are excited about a new addition to the list of species recovered from Project 23. Our first record of the freshwater limpet Ferrissia walkeri was found in the matrix from a sloth skull excavated from the Box 7 series. This well preserved complete specimen is the first mollusk species that Project 23 has added to the Rancho La Brea faunal list. Ferrissia walkeri is known from other Late Pleistocene localities in Southern California and is usually found in fragments because it is fragile.
The excavation of the main vent deposit in Box 1 is done! We have been excavating it since August 2008 and measured out 14,000 fossils from the four main grids of the deposit. That is just a preliminary number of fossils from those grids. The number of fossils will multiply significantly once the matrix has been processed due to the high concentrations of microfossils preserved that were too small to measure. All that's left where the main deposit was is a sticky pile of burlap that was used to support the deposit's bottom. The rest of Box 1 is currently on hold. The data from this deposit can will help researchers understand how large vent deposits are formed and how the animals and plants died and ended up there. The microfossils will help us understand the habitat and climate of the Los Angeles Basin 35,000 years ago. Here is a preliminary count of the minimum number of large individuals from this deposit from what has been cleaned and cataloged so far:
6 adult Dire Wolf, Canis dirus
5 juvenile Dire Wolf, Canis dirus
5 adult Sabertoothed Cat, Smilodon fatalis
8 juvenile Sabertoothed Cat, Smilodon fatalis
4 juvenile Bison, Bison antiquus
1 La Brea Condor, Breagyps clarki
1 juvenile Camel, Camelops hesternus
1 adult Grey Wolf, Canis lupus
1 adult Dwarf Pronghorn, Capromeryx minor
1 juvenile Dwarf Pronghorn, Capromerxy minor
1 adult Western Horse, Equus occidentalis
1 juvenile Western Horse, Equus occidentalis
1 adult Bobcat, Lynx rufus
1 juvenile Bobcat, Lynx rufus
1 Shasta Ground Sloth, Nothrotheriops shastensis
1 adult Naegele’s Giant Jaguar, Panthera atrox, “Fluffy”
1 Harlan’s Giant Ground Sloth, Paramylodon harlani, “George Harrison”
1 Mountain Lion, Puma concolor
3 Merriam’s Teratorns, Teratornis merriami
Aside from digging fossils at the tar pits, a preparator’s position description includes “and other duties as necessary.” A couple weeks ago, this included rescuing the floating lake pit mammoth! It had drifted south from a broken anchor and ended up mired in sediment by the sidewalk bridge, looking as if it were calling out in distress to passersby. We could have put a sign up that said "Please don't feed the mammoth!" But it really belonged back with its family and operations needed our assistance with its rescue. First, we had to "unstick" the mammoth by pulling on it with a rope and nudging it with a pole. The mammoth was then dragged to its normal area with the rope tied off to a stake to wait for its re-chaining. All in a day's work!
The above image is a kangaroo rat (Dipodomys sp.) right dentary, another notable specimen from Box 14 microfossil sorting. The roots of its inscisor and cheek teeth are partially exposed. There are 12 living species of Dipodomys in California, with eight being in Southern California.
Recently found in Box 14, this is a Harlan's giant ground sloth, Paramylodon harlani, right premaxilla, which is the part of the skull that supports the upper lip. It is the first sloth premaxilla to have been found in Project 23, and a rare element to find at Rancho La Brea. We have also found the back half of a sloth skull, vertebrae and ribs in the same deposit.
We are currently focusing on washing matrix just from Box 14 because its asphalt saturated sands contain thousands of microfossils! The image above shows an example of what we have been finding during sorting.
The above image is a recent photo of what we have been working on in box 14. Last month we measured 320 fossils, all from this deposit!
This image shows the lower left jaw of a juvenile mastodon from Box 14, aka "Little Timmy," as it occurred with other fossils in the deposit. This jaw, which is now in the Lab, is one of many elements of Little Timmy recovered from Box 14. As mastodons are rare at Rancho La Brea, and as Timmy is a juvenile, it is likely that all the immature mastodon elements from this deposit are from the same individual. Asphaltic deposits normally consist of a jumbled mass of bones from many different individuals. Identification of a rare animal leads to better understanding of the how its bones were distributed throughout the deposit, which in turn gives us insight as to how the deposits were formed.
Based on his tooth eruption, Little Timmy may be the second youngest mastodon ever found at Rancho La Brea.
Box 12, our 8th box opened, is now our 6th box completed! Volunteer Jack fills the last buckets of matrix from Box 12 in the above image. When we opened Box 12 about a year ago, I wrote in the The Excavatrix about how it had some nice examples of permineralized bone, which is rarely found at Rancho La Brea, that were loose at the surface and put into buckets at the time of the entire deposit's removal from the ground.
During the past year, this asphalt-saturated stream deposit has yielded about 90 buckets of matrix. We have found a small amount of wood, leaves, freshwater shells, and a few measured bones, including a saber-toothed cat toe and horse tooth fragment. Microfossils found included a small-sized snake vertebra and a gopher tooth.
We are now preparing to open a much larger deposit, Box 5A, which we hope will contain more of the camel and baby mammoth skeletons from its completed counterpart Box 5B!
This bird beak, recently recovered from Box 1, is from an extinct vulture of the genus Breagyps. Close in size to living condors, Breagyps has a distinctive long beak and is one of the rarer vultures from Rancho La Brea. This is the first identified element of this vulture from Project 23, and only the fourth beak ever found at Rancho La Brea.
These two thoracic (mid-back) vertebrae from a saber-toothed cat were recently excavated in Box 14. They are pathologically fused together and have other signs of arthritis. Life for this animal would have been painful but it survived successfully until it became mired in an asphalt seep. The abundance of excellently preserved fossils from Rancho La Brea helps us to piece together the life stories of the animals that used to live here.
Recently, every skull from the dire wolf skull exhibit at the Page Museum was removed so that new lights could be installed in the exhibit! During this four day process, each of the 400 skulls was taken down, cleaned, photographed, and then re-installed.
This is a proximal phalanx of a juvenile camel found in Box 14. The only camel bone previously recovered from this deposit is a juvenile femur. As camels are not very common at Rancho La Brea, and as both bones are immature, they could be from the same individual.
Volunteer Sean Campbell recently found this coyote baculum (penis bone) in Box 1. The baculum is present in male primates, rodents, insectivores, carnivores, pinnipeds, and bats. So far from Project 23 we have recovered one weasel and three dire wolf bacula. This is the first coyote baculum identified from Project 23!
This is a fragment from the plastron of a large chelonian (the group that unites turtles, tortoises and terrapins) recovered from Box 10A of Project 23. Box 10A was a small deposit with a lot of broken bones. Its excavation was completed in 2009 but not many of its fossils have been processed yet. Other elements of this individual are currently being prepared. It may represent the only tortoise species known from Rancho La Brea!
The BBC has just finished filming behind-the-scenes at the Page Museum for an upcoming three part documentary called “The Ice Age”. Presenter Dr. Alice Roberts interviewed and interacted with staff and volunteers in the collections areas, the Fishbowl Lab, and at the Project 23 excavations. With CGI animals, interesting conversations, and great footage this promises to be an exciting show. Watch out for its release in spring 2013!
According to Research Associate Chris Shaw, these marks were made by a carnivore. There are two clearly defined depressed fractures on the anterior medial (inner) surface of this ilium (part of the pelvis) and one on the lateral (outer) surface, suggesting that this animal was bitten by a carnivore hard enough for their teeth to puncture the bone. These sorts of paleo-pathologies are not very common at Rancho La Brea and this is the first evidence of possible bite marks identified from Project 23. In Box 1, excavators have found the remains of several baby bison. This individual (catalog number P23-10498) was very young when it became mired in the asphalt.
This leaf, most likely oak, was found in the hard asphalt of Box 12 last week. It is another example of the excellent preservation of plant material found at the La Brea Tar Pits, having retained its color from when it fell into the asphalt tens of thousands of years ago. Project 23 has even yielded mats of oak leaves, particularly in Box 1, in which we also find the remains of some of the detritivores who used to live in this habitat.
Deposit 1 is the first box of Project 23 that has been opened, and it is also the largest at an estimated 123,000 pounds. From the surface to its base, the deposit is just more than nine levels or 230 cm (7.5 feet). After 3½ years of digging, we have just reached the bottom of it in grid A-1!
This grid is of the Southeast portion of the large vent deposit in the Southern end of the box. Only the non-asphaltic, non-fossil dirt was removed in this grid to expose around the asphalt/fossil sediments, providing an excellent vertical view of the lower portion of the huge vent deposit, where we have measured 4,204 fossils so far.
Although we have probably excavated over 16,000 bones from Project 23, there is a backlog of preparation, identification, cataloging, and databasing all of this material. This is specimen number P23-10,001. It is a proximal anterior rib of Clyde; a semi-articulated camel from Box 5B (Camelops hesternus). Clyde’s skull and lower jaws were also found and are currently still being prepared in the Fishbowl Lab by volunteer Nola.
Camels are not very common at Rancho La Brea. They are only known from about 30 or so individuals. However, Project 23 has already yielded three different individuals; a sub-adult vertebra from Box 1, a baby femur from Box 14 and Clyde.
Discovered this week in Box 14 by volunteer Beau, this tiny fossil is a terminal phalanx of a juvenile dwarf pronghorn, Capromeryx minor. It's an element that none of us current excavators had ever come across before! In fact, out of all the 602 records of Capromeryx minor in all of the collections here, only seven are terminal phalanges. Within Project 23, there are 40 records of Capromeryx minor so far. Five have been found in Box 14 and indicate at least one adult and one juvenile in that deposit so far.
Capromeryx minor belongs to the family Antilocapridae, which are pronghorn and native to North America. This family is represented only by a single species today, Antilocapra americana. Interestingly, the extinct dwarf pronghorn is more commonly found at Rancho La Brea.
This tiny black tooth (a right lower incisor) measuring about 1mm, was just identified in the Fishbowl Lab under the microscope. It is pictured here with the complete right lower jaw of a modern specimen of long-tailed shrew (genus Sorex) for comparison. The red on the tips of the teeth is accumulated iron which may function to strengthen the enamel. The diet of a shrew consists mainly of arthropods and their closest relative is the mole. Either due to their diminutive size or their rarity in the L.A. basin, there are only 20 specimens known from the tar pits. It is not possible to tell which species this is based on this tooth.
Finally, after tens of thousands of years, our Columbian mammoth Zed’s left overgrown incisor sees the light of day. Well that is except for the few days when it was discovered and before it was covered with a protective plaster jacket. On public view in the Fishbowl Lab we have begun the process of carefully removing the protective plaster jacket to reveal the tusk. Thus far it looks to be well preserved with some asphalt on the surface between the sediment and the tusk. The preparation will probably take some time in order to protect the integrity of the dentine which flakes easily. This specimen is one of a pair that we discovered belonging to a single mammoth. They are the most complete tusks ever found and recovered from Rancho La Brea!
Among the recent discoveries at Project 23 is this exquisite left tibiotarsus (shin bone) of a large bird of prey, probably a Golden Eagle. This is no ordinary shin bone, however. As you can see, the asphalt has preserved something from the life history of this bird — a healed compound fracture in the middle of the bone. This paleopathology also shows evidence of massive infection. The interesting thing to note is that this broken leg did not kill this animal since it lived long enough to show extensive healing. There are lots of examples of healed injuries and evidence of diseases preserved in the bones at the La Brea Tar Pits — just one more reason why this collection is so special.
We are taking a break from excavating at Project 23 this morning to take care of some maintenance in Pit 91. Since this site is the lowest point in Hancock Park, water accumulates here. We are also constantly battling the seeping asphalt that clogs the drainage channels and covers the fossils. Suited up in protective gear, we are removing the asphalt by hand (known as glopping) and cleaning out the debris that has fallen in over the past few months.
Box 14 is turning out to be a very rich microfossil deposit. Careful excavation techniques revealed this articulated beetle leg still attached to its abdomen after tens of thousands of years!