Book Description

The Cretaceous corals (Anthozoa, Scleractinia) of the Huetamo region of southwestern Mexico, an area in the tectonically problematic Guerrero terrane, are investigated for the first time. This study provides a detailed, modern taxonomic foundation for future work on Mexican Cretaceous corals. Thirty-nine species are described and illustrated: 20 from the lower Aptian Cumburindio Formation, one from lower Aptian strata of the San Lucas Formation, and 18 from the upper Albian-lower Cenomanian upper member of the Mal Paso Formation. At the species level, the coral faunas from these formations are entirely different from each other. Of the 21 species from the lower Aptian, three are described as new: Saltocyathus cumburindioensis n. sp., Actinaraea michoacanensis n. sp, and Thamnarea hornosensis n. sp. About 50 percent of the lower Aptian coral species have been reported previously from pre-Albian strata in the European region. This faunal similarity is the strongest geographic affinity recognized in this study. Of the 18 coral species from the upper Albian-lower Cenomanian, 11 are described as new, whereas another one of these species recently has been described and designated as the type species of a newly recognized dendrophylliid genus, Blastozopsammia guerreroterion Filkorn and Pantoja-Alor, 2004. The 11 coral species from the upper Albian-lower Cenomanian herein described as new are: Actinastrea chumbitaroensis n. sp., Preverastraea coatlicuae n. sp., Preverastraea tocae n. sp., Latiphyllia mexicana n. sp., Thecosmilia guerreroensis n. sp., Mycetophyllopsis azteca n. sp., Orbignygyra? incognita n. sp., Thalamocaeniopsis mexicanensis n. sp., Thamnasteria tonantzinae n. sp., Paracycloseris effrenatus n. sp., and Ovalastrea malpaso n. sp. Analogies with extant corals indicate that most of the coral species from the Cretaceous formations of southwestern Mexico were zooxanthellate, hermatypic, reef-building species. Associations of scleractinian corals and rudist bivalves were observed at three localities, two in the Cumburindio Formation and one in the Mal Paso Formation. The two occurrences in the Cumburindio Formation are: an association of a large species of ramose, microsolenid coral, Thamnarea hornosensis n. sp., preserved in situ along with valves of the rudists Praecaprina and Caprina at the exposures in the Arroyo Los Hornos, near Turitzio; and a diverse assemblage of reef corals that conformably overlies a bed primarily composed of valves of the rudist Amphitriscoelus near the top of the stratigraphic section at the Loma de San Juan, Turitzio, Michoacán. The coral and rudist association in the Mal Paso Formation involves a diverse assemblage of reef corals and the rudists Radiolites and Mexicaprina within an interval near the top of the stratigraphic section that is exposed at a locality in the state of Guerrero, just north of Chumbítaro, Michoacán. None of these specific kinds of coral and rudist associations has been recognized previously at any other localities.