Early Cretaceous Multituberculata (Mammalia) from North America and Asia

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The geologic range of the mammalian order Multituberculata is from the Late Triassic to early Oligocene (approximately 195 to 35 million years ago); the group is therefore the longest- lived order of mammals known. In addition to their great longevity, multituberculates constituted one of the most abundant and diverse mammal groups during the Late Cretaceous and Paleocene (from approximately 75 to 58 million years ago). Almost nothing, however, is known about the evolutionary history of multituberculates from the Late Jurassic to the early Late Cretaceous, an interval of over 50 million years. It is during this interval that two of the three major subgroups of multituberculates arose. Although a large collection of North American multituberculates of Early Cretaceous age has been known for over 35 years, it has never been described. This collection, from north-central Texas, comprises approximately 165 isolated teeth and lies roughly in the middle of the 50 million year gap in our knowledge of multituberculate evolution. Recent field work in south-central Montana has revealed the presence of another Early Cretaceous multituberculate-bearing locality in western North America. The objectives of the research proposed here are therefore as follows: 1) to describe the collection of multituberculates from Texas and to evaluate their phylogenetic relationships to other multituberculates; 2) to conduct field work at the new locality in Montana in an attempt to find additional multituberculate specimens from this crucial interval of time but from a different geographic region within North America; and 3) to perform a detailed analysis of dental function and jaw movement of Early Cretaceous multituberculates to determine their dietary proclivities.