LATE CRETACEOUS (MAASTRICHTIAN) CORALS FROM CHIAPAS, MEXICO

Fossil corals recently have been discovered in Maastrichtian strata of the Ocozocuautla Formation, central Chiapas, Mexico. This is the initial report on the taxonomic composition of the coral fauna and the first record of these coral species (except for two) in Mexico. The Ocozocuautla Formation, at the localities examined in the vicinity of Tuxtla Gutiérrez, is composed of medium- to thick-bedded limestone and marl with intercalations of carbonaceous grey shale. The Maastrichtian age assignment for these strata is supported by fossils of several other groups, including dasycladacean algae (e.g., Neogyroporella), larger foraminifera (e.g., Chubbina), ostracodes, decapods, gastropods, rudists (e.g., Titanosarcolites) and other bivalves, that also occur in the Ocozocuautla Formation.

The coral fauna is composed of colonial, reef-building species and several solitary species. The colonial species exhibit a broad array of corallum growth forms, including ramose, massive, encrusting and phaceloid. The identified colonial coral species, in order of decreasing abundance, are: Multicolumnastraea cyathiformis (Duncan, 1865); Actinhelia elegans (Goldfuss, 1826); Dictuophyllia conferticostata (Vaughan, 1899); Barysmilia trechmanni (Wells, 1934); Cladocora jamaicaensis Vaughan, 1899; Synastrea sp. cf. S. agaricites Goldfuss, 1826; Favia? gregoryi Wells, 1935; Mesomorpha catadupensis Vaughan, 1899; and Actinastrea sp. The solitary coral species are Paracycloseris elizabethae Wells, 1934, which is abundant and occurs in discoid, patellate and cylindrical growth forms, and, less commonly, Trochoseris catadupensis Vaughan, 1899, and Trochosmilia hilli Vaughan, 1899, both of which are pedunculate.

Most of the coral species from the Maastrichtian of Chiapas have been reported previously from only a few other localities within the Caribbean region: in the Maastrichtian Guinea Corn Formation of Jamaica; the Campanian - Maastrichtian of Cuba; and two other sites (one species at each) in Mexico. Preliminary analysis indicates that all but one of the coral species listed above became extinct by the close of the Cretaceous Period. Only Favia? gregoryi Wells, 1935, is known from the Tertiary (middle Eocene, Jamaica): its occurrence in the Maastrichtian of Chiapas is the earliest known record of the species.