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Late Pleistocene Freshwater Fishes from the Rancho La Brea Deposit, Southern California





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Three species of Pleistocene freshwater fishes occur at Rancho La Brea, the type deposit of the Rancho La Brea Age MammaHan faunas. Remains of rainbow trout, Salmo gairdneri, (mostly isolated vertebrae) and threespine stick- leback, Gasterosteus aculeatus (primarily pelvic spines), are both common. One dentary and two vertebrae represent one individual of arroyo chub, Gila orcutti. Based on pelvic and dorsal spine morphology, a relatively unarmored form of stickleback (possibly representing the recent Gasterosteus aculeatus williamsoni) existed in the Los Angeles Basin up to 30,000 years ago. Collectively the fish fossils indicate local, permanent stream conditions, and not stream transport from distant mountainous areas 10-30 km away. Absence of the more montane Ca- tostomus santaanae and Rhinichthys osculus also argues against long-distance transport. As with other ectothermic organisms (and possibly small endotherms), no extinct freshwater fishes are known from the Rancho La Brea deposits.