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The Pronghorn 'antelope' (Antilocapra) of western North America have long been enigmatic because they are the second-fastest modern land mammal with no natural predators that come close to matching their speed. With the discovery of the now-extinct North American cheetah, Miracinonyx , the hypothesis was put forward that the incredible speed of pronghorns was related to being the primary prey of the fleet-footed Miracinonyx. However, there has been no direct means to test that relationship. Here, utilizing organic-molecule-rich bones from Natural Trap Cave, it is possible to test the predator-prey relationship between Antilocapra and Miracinonyx through isotopic analysis of bone collagen. Offsets in carbon and nitrogen isotopes between predator and prey are used to establish or discount predator-prey relationships between common predators found in Natural Trap Cave including wolves (Canis), cheetah-like cats (Miracinonyx), and North American lions (Panthera) with prey species like horses (Equus and Haringtonhippus), pronghorns (Antilocapra), sheep (Ovis), and bison (Bison). Results provide support the hypothesis that Miracinonyx preyed upon Antilocapra , but not exclusively. Antilocapra was also important prey for lions and wolves. Wolves appear to have fed more often on horses than lions or cheetahs. [ABSTRACT FROM AUTHOR]

Abstract: Climate models provide estimates of climatic change over periods of time in the ancient past. Macrophysical climate models (MCM) differ from the more widely used general circulation models (GCM), in that MCMs provide temporally high-resolution (~100years) and site-specific estimations of monthly values of climate variables such as temperature and precipitation. In this paper, seasonal changes in climate variables are modeled for six 14C-dated fossil localities in North America. Five of these localities represent the time of maximum extent of ice during the most recent glacial episode, the Full Glacial (25+–15ka), including one at the peak of the Last Glacial Maximum (17–15ka). The other locality represents the time as the ice began to recede, the Late Glacial (15–11ka). Seasonal variations in temperature and precipitation modeled by MCM are herein compared with interpretations of seasonal variation based upon oxygen isotopes from serially sampled hypsodont teeth (mostly Equus and Bison) collected from each of these localities. Additionally, the MCM-modeled seasonal variations are used to predict the expected abundances of different plant functional groups (PFG) during those times, especially C3 and C4 functional groups, using modern relationships. These predictions are compared with carbon isotopic values from the same teeth. The importance of atmospheric pCO2 for the relative abundance of plants utilizing the C4 metabolic pathway is discussed, given that glacial episodes are known to have been times of lower atmospheric pCO2. Interpretations of seasonal variability and the relative abundance of C3 versus C4 vegetation based upon isotopes from tooth enamel are in broad agreement with predictions using the MCM and the modern distribution of PFGs with climate variables. The influence of pCO2 on the distribution of C4 vegetation during glacial times appears to be negligible. [Copyright &y& Elsevier]