Permian brachiopods from Chiapas, Mexico: new stratigraphical and paleobiogeographical insights

Eleven brachiopod species from the Paso Hondo Formation in the Chicomuselo region of southern Chiapas, Mexico are described. Chonosteges cooperi is a new species. Dyoros (Tetragonetes) rectangulatus, Costispinifera rugatula, Echinosteges tuberculatus, Tropidelasma furcillatum, Acosarina rectimarginata, Tautosia transenna, Composita hapsida, and Neospirifer venezuelensis are recorded for the first time in Mexico. The brachiopods occur in a locality to the east of the town of Monte Redondo, deposited in limestone and argillaceous limestone. The associated biota is composed of different filter feeders, with diverse invertebrates (rugose corals, microconchids, hederelloids, bryozoans, and crinoids) recorded. Lithological traits and features of the fossils allowed the facies to be assigned to a shallow open marine paleoenvironment, within a homoclinal ramp. Brachiopods recorded at the locality allow the upper levels of the Paso Hondo Formation to be correlated with the Cherry Canyon and Road Canyon formations of Texas in the United States, which have been characterized as typical stratigraphic units from the Guadalupian of North America. This information indicates that the age of the Paso Hondo Formation can be extended from the Early Permian to the Roadian (early Guadalupian), making this the first report of a formation of this age in southeastern Mexico. The presence of typical taxa from the Middle Permian in both Chiapas and Texas suggests that those regions were closely connected during the late Paleozoic, at least during the early Guadalupian. The similarity of Mexican biota to coeval faunas of Texas indicates that the brachiopods found in Chiapas occurred in the Grandian Province during the Middle Permian, which also included Texas and New Mexico, Guatemala, Venezuela, and northwest Mexico.