Stereochilus

Abstract: THE occasion of the third decennial Conference on the Biology of Plethodontid Salamanders, and the first publication of the proceedings of the conference, is a propitious time to take stock concerning diverse phylogenetic and taxonomic issues. As background, the monograph of Cope (1889) is used as a point of departure. Cope recognized a family Desmognathidae (for Desmognathus) and a family Thoriidae (for Thorius), both distinguished from the Plethodontidae by having opisthocoelous vertebrae. Within the Plethodontidae he recognized two groups of genera: Plethodontae [Plethodon, Hemidactylium, Batrachoseps, Stereochilus, and Autodax (= Aneides)], and Spelerpes [Geotriton (= Hydromantes), Gyrinophilus, Manculus (now included in Eurycea), Spelerpes (Eurycea and Pseudotriton), Oedipina, and Oedipus (supergenus Bolitoglossa, minus Oedipina and Thorius)]. The fundamental distinction was that the Plethodontae has a tongue attached anteriorly, while Spelerpes has a free tongue. Cope thought that "The generic relationships of the abovenamed groups are exceedingly simple, and the ease with which the animals can be analyzed renders the case free from the doubts which constantly arise in discussions of generic relationships as to the probable omission of characters from the argument" (Cope, 1889:121-122). The famous monograph of Dunn (1926) remains useful today. Dunn documented the unique features of the family, discussed relationships to other families, and included a lengthy treatment of relationships of species within some of the genera (e.g., Desmognathus), and of the genera to each other. Only 16 genera and 72 species were recognized. Dunn noted that Desmognathus and Leurognathus differed from the other genera in many respects, but he chose not to recognize any taxa between genus and family. Dunn envisioned two "main groups" of genera along the lines of Cope's groups-a Plethodon group with attached tongues and a Eurycea group with free tongues, "connected by three intermediate genera which hardly belong to either group" (Dunn, 1926:22)-Stereochilus, Typhlotriton, and Typhlomolge. Apart from the recognition of many more species and a few novel new genera, the largest difference between the taxonomy of today and that of Dunn is his treatment of tropical salamanders. He recognized only 31 tropical species (about 44% of the total number of species of plethodontids; tropical species constitute more than 65% today), all placed in Oedipus. While workers such as Noble (1927, 1931) quibbled with some of Dunn's ideas, the monograph remained authoritative for several decades. Taylor (1944) described many tropical species and sorted them into a number of genera. Several new genera (e.g., Phaeognathus, Haideotriton) and many new species were named in North America as well, but it was not until my comparative osteological study (Wake, 1966) that there was a major change in taxonomy and phylogenetic perspective. That work was published on the eve of the cladistic revolution, and while most taxa are monophyletic and based on shared derived character states, there are some inconsistencies with respect to modern cladistic methodology (e.g., in the brief discussion of familial relationships). The main results of that study have remained surprisingly robust and find wide acceptance to this day. Wake (1966) thought that plethodontids were derived from an ambystomatid ancestral stock (in 1966 the Ambystomatidae included the three subfamilies Ambysto-