IDENTIFICATION OF NEW-WORLD AGONUM, REVIEW OF THE MEXICAN FAUNA, AND DESCRIPTION OF INCAGONUM, NEW GENUS, FROM SOUTH-AMERICA (COLEOPTERA, CARABIDAE, PLATYNINI)

A key for the identification of the 74 species of Agonum Bonelli in th e New World is presented along with taxonomic treatments of the 15 spe cies occurring in Mexico. Neotypes are designated for Agonum orbicolli s Say (=A. punctiforme Say) and Agonum suturale Say. Diagnosis of Agon um based on external characters, and characters of the male and female genitalia and reproductive tract, necessitates removal of South Ameri can species previously considered congeneric to a new genus, Incagonum (type species Anchomenus discoculcatus Dejean). Synapomorphies establ ishing monophyly of Incagonum include reduced subapical elytral sinuat ion, and female spermatheca with digitate basal lobe. The absence of s ubapical setae on metatarsomere 4, and presence of a short but distinc t spermathecal duct support the monophyly of Incagonum plus other taxa in the previously proposed Rhadine-Tanystoma lineage. Removal of Inca gonum species from Agonum results in restriction of Agonum to lands pr eviously comprising Laurasia, or to regions broadly accreted to its so uthern margin. Cladistic biogeographic analysis of the Mexican Agonum fauna and other carabid taxa exhibiting Halffter's Nearctic pattern do not contradict a primary division of the Mexican biota into a norther n portion, including the Sierra Madre Occidental and Oriental and asso ciated lowland regions, and a southern portion including the Transvolc anic Sierra and Sierra Madre del Sur. The analysis recognizes an area of endemism comprising the southern Sierra Madre Occidental. This area exhibits ambiguous area relationships with areas to the north and sou th. The included Nearctic pattern taxa also provide only ambiguous inf ormation concerning the area relationships for areas north of the Isth mus of Tehuantepec versus the Chiapan highlands.