Gauthier is the son of Edward Paul Gauthier and Patricia Marie Grogan. He received a B.S. degree in zoology at
San Diego State University in 1973, a master's in biological science at the same institute in 1980, and a PhD in paleontology from the
University of California, Berkeley, in 1984. Currently he is a professor of geology and geophysics and ecology and evolutionary biology and curator of vertebrate paleontology and vertebrate zoology at
Yale University. His master's thesis, the content of which was published in 1982, is a classic work on the paleontology and phylogeny of the lizard clade
Anguimorpha that remains a core reference for morphological research on
Xenosauridae and
Anguidae in particular. His PhD thesis constituted the first major
cladistic analysis of
Diapsida, as well as arguing for the
monophyly of the
dinosaurs. He followed this with an important paper on the origin of
birds from
theropods. This was the first detailed cladistic analysis of the theropod dinosaurs, and initiated a revolution in dinosaur
phylogenetics, in which cladistics replaced the Linnaean system in the
classification and phylogenetic understanding of the dinosaurs. Gauthier's corpus contributed the foundational phylogenetic studies of
Archosauria and
Lepidosauria, two major amniote clades; and he was the primary author of the foundational and still widely cited phylogenetic study of
Amniota as a whole. The phylogenetic character sets from his 1984 and 1986 works, the 1988 amniote paper, and the 1988 lepidosaur and
squamate papers still form the core of essentially all gross-anatomy-based phylogenetic analyses of these groups, and as such are among the most highly cited papers in amniote morphology and paleobiology. The 1988 amniote paper is also frequently cited to demonstrate the importance of taxon sampling in phylogenetic analysis, in particular the importance of sampling rare or fossil taxa that can break 'long branches' along which convergence can occur. Gauthier has argued together with
Kevin de Queiroz for replacing
Linnaean taxonomy with the
PhyloCode. In addition to his theoretical work on systematics and taxonomy, Gauthier continues to study the anatomy and relationships of diapsids, particularly lepidosaurs. His lizard work currently focuses on
Scincomorpha, following on a career-long interest in the unusual clade
Xantusiidae. He is a principal investigator on the
National Science Foundation-funded effort to reconstruct the phylogeny of lizards and snakes (
Squamata) using gross anatomy and molecular structure, building on his earlier work in collaboration with Richard Estes and Kevin de Queiroz, which established the most widely accepted phylogeny of the group. ==Footnotes==