MIOCENE DECAPOD CRUSTACEA FROM AMBER BEARING DEPOSITS IN CHIAPAS, SOUTHERN MEXICO; STRATIGRAPHIC IMPLICATIONS

Amber deposits from La Quinta Formation, Simojovel, Chiapas, Mexico are known worldwide for their diverse flora and insect faunas. Although sandstones containing amber are rich in molluscan remains no decapod crustaceans have ever been reported. Newly discovered decapod crustaceans, associated with amber, were recently collected from two localities near Simojovel. The decapod crustacean families Calappidae, Hepatidae, Parthenopidae, and Hexapodidae have tentatively been identified. Dorsal carapaces are usually preserved in the form of molts. Based on biostratigraphic ranges of molluscan species a middle Miocene age is proposed for the La Quinta Formation. Similar molluscan species have been identified from the middle Miocene Tuxpam Formation, Veracruz, Mexico. Age definition is important for the La Quinta Formation because the amber contained within the formation has long been considered Oligocene-Miocene. A complete study of the systematics and biostratigraphy of decapod crustacean and molluscan species from the La Quinta Formation will enable the depositional environment, paleoenvironment reconstruction, and conformation of the formation age. This discovery documents the second occurrence of Miocene decapod crustaceans from Mexico. The other Miocene unit that includes decapod crustaceans is the Tuxpam Formation, Veracruz state, Mexico. Species within the families Portunidae and Raninidae represent the decapod crustacean assemblage of the Tuxpam Formation