First record of Ubaghsicystis (Eocrinoidea - Echinodermata) from the Cambrian (Miaolingian, Wuliuan) of Sonora, Mexico: Biostratigraphical and paleoecological considerations

Introduction: The present work constitutes the first record of Ubaghsicystis Gil-Cid & Domínguez-Alonso (Echinodermata-Eocrinoidea) in El Gavilán Formation, exposed Sahuaral Hill, a new Cambrian locality central Sonora, Mexico. Formation is sedimentary sequence mainly made up shale interbedded with limestone, abundant invertebrate fossils, deposited an open shelf marine environment. Objective: main objective this research to describe species cf. U. segurae for time Mexico, addition biostratigraphic and paleoecological considerations. Methods: A composite stratigraphic section Fm. was measured where samples corresponding eocrinods were collected, material examined Microscope Leica MZ10. Results: biotic association composed reticulosan sponges, chancelloriids (Chancelloria eros, Allonnia tintinopsis, Archiasterella sp.), hyolithids, brachiopods, trilobites (Quadragnostus depressa, Peronopsis sp., Tonkinella valida, Elrathina echinoderms (Ubaghsicystis segurae). Regarding age, trilobite establishes chronostratigraphic position from middle (Miaolingian, Wuliuan), Altiocculus Subzone, Ehmaniella Zone. studied constituted by isolated echinoderm plates, which probably represent various cycles theca plates assigned segurae. genus has been scarcely recorded few regions (e.g., Burgess Shale Canada Los Barrios de Luna Spain), so that information about taxon limited. Conclusions: succession occurred, part border Laurentia craton during period, located near Paleoequator ideal conditions increasing diversity abundance developed, including echinoderms.