A new genus and species of sphaeromatid (Crustacea: Isopoda) from the Lower Cretaceous (Aptian) Sierra Madre Formation, Chiapas, Mexico

Chiapasphaera cretacea Vega and Bruce gen. et sp. nov. is described from the dolomitic laminar plattenkalk deposits of the Aptian Sierra Madre Formation at El Espinal quarries, Chiapas, Mexico. The new isopod is represented by more than 50 specimens of diverse size, but with a mean length of about 10 mm and 0.4 mm width. Isopods are preserved as corpses in dorsal and ventral views, as well as a moults and rolled individuals, The morphology resembles that of the extant genus Gnorimosphaeroma, but differs principally in having five visible pleonites, warranting the erection of a new genus and new species. Poor preservation of appendages prevents a more detailed description, but details of pereon, pleon, pleotelson and uropods are clear enough to offer important taxonomic features. This is the sixth isopod species reported from the El Espinal quarries.