SOME ADDITIONS TO THE FOSSIL DECAPOD CRUSTACEANS OF THE MIOCENE TUXPAM FORMATION, VERACRUZ, MEXICO

Fossil decapod crustaceans from the Miocene Tuxpam Formation of Veracruz, Mexico are scarce in comparison to the large described fauna of bivalves, gastropods, and echinoderms. Previous descriptions of fossil decapod crustaceans from the Tuxpam Formation have included Raninoides mexicanus, Portunus atecuicitli, Necronectes tajinensis, and calappid cheliped fragments. In this paper we report two new localities that contain fossil decapod crustaceans. The first locality is near the town of Copalar de Zaragoza, in a sequence of sandstones and clays. Here, a new species of the genus Ranina were collected. The arrangement of the frontal orbital spines is very similar to the extant and only living species of the genus, Ranina ranina from the Indo-Pacific. This find marks the second fossil occurrence of Ranina in Mexico, the other occurrence is from the middle Eocene of Baja California. The second locality is in a new road cut along the Poza Rica-Mexico City highway. Tentative collections from this locality have produced shark teeth, molluscs, gastropods, and a single, large portunid crab. The new crab is confidently assigned to the family Portunidae, however placement into existing subfamilies and genera of the family Portunidae is difficult because the arrangement of the frontal spines and anterolateral spines of this portunid specimen is distinctly different from any fossil or extant species assigned to the family at this time. Interestingly, this new portunid crab is very similar, most likely belonging to the same genus, as the new portunid crab collected from Simojovel, Chiapas state, Mexico. This marks the first time a correlation can be made between formations in Mexico based solely upon fossil decapod crustaceans. Stratigraphic correlation between Miocene formations in eastern central and southern Mexico will be an important tool for paleogeographic reconstruction. These new localities are also important because, due to population growth, the type section of the Tuxpam Formation is being destroyed. Therefore correlation of the type section of the Tuxpam Formation with these new localities is important in furthering the collection and scientific additions to the fauna, including fossil decapod crustaceans, of the Tuxpam Formation.