Rancho La Brea Tar Pits

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As one of the world's most famous concentrations of late Pleistocene fossils these tar seeps have yielded some 50 species of mammals, 125 birds, 16 herptiles and a scattering of molluscs, insects and other invertebrates.

Among the mammals, carnivores account for over 90 percent of the individual remains which are primarily of extinct species. The most numerous remains belong to the dire wolf, Canis dirus, followed by the sabre-toothed cat, Smilodon californicus. The largest carnivores were the short-faced bear, Tremarctotherium simum, and the lion-like cat, Panthera atrox.

The prey, though not as abundant, is far more diverse and includes the Western horse, Equus occidentalis, tapir, Tapirus sp., a peccary-like animal, Platygonus sp., camel, Camelops hesternus, an antelope, Breameryx minor, bison, Bison antiquus, mastodon, Mammut americanus, two mammoths, Mammuthus imperator and Mammuthus columbi, and three ground sloths, Paramylodon harlani, Nothrotherium shastense, and Megalonys jeffersoni californicus. There are also fossils of a number of species still found in the State.

As with the mammals, most–60 percent–of the individual remains of the birds are those of raptors. Noteworthy is the condor-like vulture, Teratornis merriami, which had a wing span of at least 3.6 meters (12 feet) and which ranks among the largest known flying birds. Six other vulturine fossils have been found here including Gymnogyps amplus, the ancestor of the California condor, Gymnogyps californianus, and two vultures related to the old-world vultures; the latter are not found in North America today. At least 19 other species of raptors have been identified, including several extinct forms related to living Southern Hemisphere species. The Galliformes, which include a large extinct turkey, Parapavo californicus, and the still extant quail, Lophortyx californica, rank second in number of individuals.

Two of the more interesting reptiles are the desert scaly lizard, Sceloporus magister, and the yucca night lizard, Xantusia vigilis, desert species not found in the Los Angeles basin today.

Plant remains are scant compared with the Carpinteria deposits (see Carpinteria Asphalt Deposits). Remains of coast live oak, Quercus agrifolia, pine, possibly Pinus muricata, cypress, Cupressus sp., juniper, Juniperus californica, Arctostaphylos sp., and elderberry, Sambucus , have been found here. The vegetation suggests a climate somewhat warmer, with a greater annual rainfall than today. Thus the cool, humid flora which extended southward along the coast during the late Pleistocene includes a warmer, interior element at Rancho La Brea.

The asphaltic exudation is from the Tertiary Fernando group which is penetrating the Pleistocene alluvial deposits. These outpourings were most active during the late Pleistocene, hence the predominance of species of this age; however, they are still active on a much lesser scale. (See also McKittrick Tar Pits .)

Integrity: A City Park with numerous buildings, paths, etc. Excavations are in progress.

Use: Research, educational.

Ref: Stock, Chester, 1972. Rancho La Brea: A Record of Pleistocene Life in California. L.A. County Mus. of Nat. Hist. Sci. Series No. 20, Paleo. No. 11.

October 1975