The gray wolf (Canis lupus) is one of the few large predators to survive the Late Pleistocene megafaunal extinctions [1]. Nevertheless, wolves disappeared from northern North America in the Late Pleistocene, suggesting they were affected by factors that eliminated other species. Using skeletal material collected from Pleistocene permafrost deposits of eastern Beringia, we present a comprehensive analysis of an extinct vertebrate by exploring genetic (mtDNA), morphologic, and isotopic (delta(13)C, delta(15)N) data to reveal the evolutionary relationships, as well as diet and feeding behavior, of ancient wolves. Remarkably, the Late Pleistocene wolves are genetically unique and morphologically distinct. None of the 16 mtDNA haplotypes recovered from a sample of 20 Pleistocene eastern-Beringian wolves was shared with any modern wolf, and instead they appear most closely related to Late Pleistocene wolves of Eurasia. Moreover, skull shape, tooth wear, and isotopic data suggest that eastern-Beringian wolves were specialized hunters and scavengers of extinct megafauna. Thus, a previously unrecognized, uniquely adapted, and genetically distinct wolf ecomorph suffered extinction in the Late Pleistocene, along with other megafauna. Consequently, the survival of the species in North America depended on the presence of more generalized forms elsewhere.

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Isotopic studies of palaeoecological and ecological questions often use bone collagen or bioapatite as substrates, but rarely both. Substantial new information can be gained from the incorporation of isotopic values from both the organic and inorganic fractions of bone. Here we show that combining isotopic data from both substrates provides valuable and unique insights into (1) trophic relationships and dietary interactions; (2) differences in digestive physiologies and (3) identification of palaeontological or archaeological remains that lack diagnostic morphological characters. We present a range of new isotopic data collected from modern and fossil mammals, and investigate patterns within several published datasets. We define carbon isotope spacing variables, and then explore four diverse palaeoecological and ecological case studies.