- The Paleontological Society
The seventy-fifth anniversary of the Journal of Paleontology presents a felicitous opportunity to review major changes in interpretation of mammalian phylogeny. Founding of the journal coincides with the nascence of the career of the most influential paleomammalogist of the past century, George Gaylord Simpson (1902–1984). It occurred at a time when now-archaic models for mammalian systematics and evolution, such as the aristogenesis of H. F. Osborn (1857–1935) and the typological concept of taxa, were prevalent (e.g., Simpson, 1945). These models were soon to give way to “new ways of going at things” (Laporte, 2000, p. 87); most significantly, the incorporation of quantitative methods and the evolutionary synthesis (Simpson, 1944). Subsequent decades witnessed the rise and/or sophistication of other applications and perspectives in fossil-based interpretation of mammalian systematics, including form-function analysis (e.g., Szalay, 1994) and, particularly, cladistic approaches (e.g., McKenna, 1975). Within these broad ideological frameworks, major paradigm shifts have resulted from new discoveries, conceptual changes, or (most commonly) a combination of both. Finally, mammalian systematics currently lie at the verge of a monumental paradigm shift, providing important direction for the future.
Given the brevity of this review, I focus mainly on the base and early branches of the mammalian tree: separate chapters would be required to undertake more than superficial coverage of Cenozoic radiations of placentals and marsupials. Likewise, despite the increasingly important role that molecular data have come to play in interpreting mammalian relationships (e.g., summary by Novacek, 1993), I deal here mainly with the primary subject matter of the journal itself: the fossil record. For organizational purposes, it is convenient to follow some broad systematic framework for mammals, notwithstanding the fact that placement of several major groups is unsettled and the subject of intense debate. Herein, I generally follow the phylogeny proposed by Luo et al. (2001) …