New Late Cretaceous, North American advanced therian mammals that fit neither the marsupial nor eutherian molds
Published:January 01, 1986
William A. Clemens, Jason A. Lillegraven, 1986. "New Late Cretaceous, North American advanced therian mammals that fit neither the marsupial nor eutherian molds", Vertebrates, Phylogeny, and Philosophy, Kathryn M. Flanagan, Jason A. Lillegraven
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Upper molars of two new genera and species of mammals (Falepetrus barwini and Bistius bondi) are described from rocks of Late Cretaceous age of Montana, Wyoming, and New Mexico. Although these teeth are evolutionarily advanced in being fully tribosphenic, they have combinations of characters that preclude identification of the animals that bore them as either marsupials or eutherians. A review of available dental features useful in classification of known, fully-tribosphenic mammals from the Late Cretaceous suggests the presence of four principal groups: (1) Marsupialia; (2) Eutheria; (3) “deltatheridians;” and (4) others. Groups “ 1 ” and “2” are recognized as formal taxonomic units, defined by anatomically diverse suites of derived characters. Groups “3” and “4” are recognized informally and, as a grade, dubbed “tribotheres,” mammals with tribosphenic dentitions lacking documented specializations characteristic of either marsupials or eutherians. Although group “3” may represent an evolutionary clade equivalent in taxonomic rank to marsupials or eutherians, members of group“4” (including Falepetrus and Bistius) comprise a heterogeneous conglomeration whose members have uncertain relationships to members of groups “1-3.” In addition to the evolutionary radiations of contemporary marsupials and eutherians, the tribotheres provide evidence of at least a third, if not several, broad mammalian radiations during the Cretaceous. However, available dental criteria are inadequate to allow development of a useful, phylogenetically-based classification of the tribotheres.
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Vertebrates, Phylogeny, and Philosophy
Dr. George Gaylord Simpson, one of the most important evolutionary biologists of the Twentieth Century, was born on June 16, 1902 and died on October 6, 1984. His contributions to science include not only a modern synthesis of evolutionary thought, but original research on anthropology, mammalogy, paleontology, general biology, and statistics. His prolific writings were intended for scientific and non—scientific communities alike. He helped and encouraged many who now work in the fields of paleontology and evolutionary biology. Contributors to this book dedicate their efforts as tribute to his memory.
Included authors are colleagues, former students, and friends of Dr. Simpson’s. They represent but a few of the people he would have included in these categories. The book is intended to suggest only a sampling of the diversity of George Gaylord Simpson's impact on present vertebrate paleontology, from its most senior to its very junior participants.
Ms. Flanagan’s letter of invitation entreated the following from potential authors: "In the spirit of Dr. Simpson’s own writings, we encourage imaginative contributions that would be just a little different from items expected in a regular scientific journal." The title of the volume (Vertebrates, Phylogeny, and Philosophy) reflects that request. Though individual articles deal almost exclusively with fossil mammals, emphases cross the spectrum of evolutionary biology, including systematic paleontology, considerations of adaptation, ontogeny, analyses of evolutionary tem— po and mode, biogeographic procedure, and paleogeography. Philip Gingerich’s contribution stresses the crucial importance of solid empirical research to the foundations upon which theoretical/philosophical writings should be based. Mesozoic and Cenozoic taxa are considered, and two articles discuss the modern union of molecular biology, genetics, and paleontology. Most articles benefited directly from the pioneering writings of George Simpson, yet the breadth of concerns of this volume covers only a small fraction of the interests exhibited in his lifetime of evolutionary research.
Kathryn Flanagan served as principal correspondent with authors and reviewers. Jason Lillegraven had principal responsibility for manuscript editing and considerations of production.
We take this opportunity to thank the thirty-two authors for their contributions. Similarly, more than fifty individuals served as unpaid reviewers, and we give our most sincere thanks for their generosity of time and effort. Also, we thank Linda E. Lillegraven for creating the cover design.