Discinid brachiopods (Lingulida, Discinoidea) of the Ixtaltepec Formation, Carboniferous of the Santiago Ixtaltepec area, Oaxaca

Four species of discinid brachiopods of the genus Orbiculoidea present at different levels of the Ixtaltepec Formation, type section Arroyo las Pulgas, Nochixtlan Municipality, Oaxaca are described. Orbiculoidea caneyana and Orbiculoidea sp. were found in basal levels of the formation, in shale strata of chesterian age (Late Mississippian). The presence of Orbiculoidea missouriensis and Orbiculoidea capuliformis in upper stratigraphic levels, and also in argillaceous rocks of morrowan-desmoinesian age (Middle Pennsylvanian), corroborate the age of the fossil-bearing rocks. These are the first records of Orbiculoidea caneyana and O. capuliformis in Mexico and, along with O. missouriensis, highlight the paleobiogeographic relationship of the carboniferous faunas of Nochixtlan with coeval faunas described in the east-central region of the United States.