About Rancho La Brea Invertebrates | Natural History Museum of Los Angeles

Invertebrates at Rancho La Brea

Large numbers of invertebrates have been recovered from Rancho La Brea, in particular from Pit 91. These include more than 45,000 specimens of mollusks (clams and snails) representing 31 species and well over 100,000 arthropods. The presence of both freshwater clams and snails suggest derivation from several different aquatic habitats ranging from shallow fast-flowing streams to stagnant ponds. Today, the land dwelling snail species live at higher elevations than the Los Angeles basin, indicating that the climate may have been cooler and moister than it is today. Arthropods include Scorpionida (scorpions), Araneida (spiders), Ostracoda (ostracods), Isopoda (isopods) and Diplopoda (millipedes) as well as seven orders of insects: Odonta (dragonflies), Orthoptera (grasshoppers and crickets), Isoptera (termites), Hemiptera (true bugs and cicadas), Coleoptera (beetles), Diptera (flies), and Hymenoptera (ants and wasps). Thus far, beetles are the most commonly recovered insects, representing 25 families. Many of the invertebrate fossils recovered are land dwellers and would not be preserved under normal conditions. A large number of the beetles and flies were carrion feeders and became trapped while feeding on carcasses of the larger animals that got stuck in the asphalt. The diversity and the different life-cycle stages of these insects are evidence indicating that decaying large animals lay on the surface of the asphalt for up to five months. Most of the fossil invertebrates found here represent living species although they may not live in Los Angeles today.