89 doi:10.4072/rbp.2018.2.01 Revista Brasileira de Paleontologia, 22(2):89–96, Maio/Agosto 2019 A Journal of the Brazilian Society of Paleontology MARGINAL MARINE TRACE FOSSILS FROM THE CÁRDENAS FORMATION (MAASTRICHTIAN), RAYÓN MUNICIPALITY, SAN LUIS POTOSÍ, CENTRAL MEXICO ARTURO PALMA-RAMÍREZ Léxico Estratigráfco de México, Departamento de Estratigrafía, Servicio Geológico Mexicano, Blvd. Felipe Ángeles km. 93.50-4, Col. Venta Prieta, C.P. 42083, Pachuca, Hidalgo, México. arctoduspr@gmail.com ROBERTO CARLOS MALDONADO-SARABIA Gerencia Regional Centro, Servicio Geológico Mexicano, Av. Mariano Jiménez 465, Col. Alamitos, C.P. 78280, San Luis Potosí, San Luis Potosí, México. robertomaldonado@sgm.gob.mx MATTHEW R. STIMSON Geology/ Paleontology Section, New Brunswick Museum, 277 Douglas Ave, Saint John New Brunswick E2K 1E5, Canada. matt.stimson@nbm.mnb.ca ABSTRACT – The State of San Luis Potosí, Mexico, is rich in fossils and has a long-standing tradition of paleontological research. Nevertheless, most of these studies have been focused on vertebrates and invertebrates body fossils, with the ichnological record being overlooked. Here, we report the occurrence of ichnofossils (Diplocraterion parallelum, Ophiomorpha nodosa, Skolithos linearis, and Palaeophycus tubularis) from the Upper Cretaceous (Maastrichtian) Cárdenas Formation, southeastern San Luis Potosí. Invertebrate trace fossils and associated body fossils suggest that the Cárdenas Formation was deposited in a low to high energy system, with occasional storm events, in a shallow water platform (delta plain or coastal paleoenvironment infuenced by tidal action). Keywords: ichnofossils, shallow water, Maastrichtian, Cárdenas Formation, Mexico. RESUMO – O Estado de San Luis de Potosí, México, é rico em fósseis e tem uma longa tradição de pesquisa paleontológica. No entanto, a maioria desses estudos tem sido focada em fósseis de vertebrados e invertebrados, com o registro icnológico sendo negligenciado. Aqui, nós reportamos a ocorrência de icnofósseis (Diplocraterion parallelum, Ophiomorpha nodosa, Skolithos linearis e Palaeophycus tubularis) do Cretáceo Superior (Maastrichtiano) Formação Cárdenas, sudeste de San Luis de Potosí. Icnofósseis de invertebrados e demais fósseis associados sugerem que a Formação Cárdenas foi depositada em um sistema de baixa a alta energia, com eventos ocasionais de tempestades, em uma plataforma de águas rasas (paleoambiente delta de planície ou costeiro, infuenciado pela ação das marés). Palavras-chave: icnofósseis, águas rasas, Maastrichtiano, Formação Cárdenas, México. INTRODUCTION Several works have shown the importance of invertebrate traces in paleontology, sedimentology, and stratigraphy (Pemberton et al., 1992, 2000, 2002; MacEachern et al., 2012). Biogenic structures in subaqueous regimes are primarily controlled by substrate consistency, sediment grain size, energy conditions, water turbidity and salinity, depositional rates, oxygenation levels, and temperature (Ekdale & Mason, 1988; MacEachern et al., 2012), and are considered good indicators of sedimentary environments (MacEachern et al., 2012). The Cárdenas Formation is a very rich fossiliferous unit and its diverse faunal assemblages have been studied by several authors, most of them focused on echinoderms (Marín-Ávila, 2012; Myers, 1968; Navarro-Moctezuma, 2004), corals (Navarro-Moctezuma, 2004; Baron-Szabo et al., 2006), brachiopods (Myers, 1968; Pérez-Martínez, 2010), foraminifers (Carrillo-Bravo, 1971; Caus et al., 2002; Omaña et al., 2008, 2012), crustaceans (Vega et al., 1995), ostracods (Caus et al., 2002), rudists (Oviedo-García, 2005; Pons et al., 2013; Schafhauser et al., 2003), and ammonites (Ifrim et al., 2005). Previous works on ichnology of the Cárdenas Formation (Zimbrón-Uresti & Alvarado-Valdez, 2015; Zimbrón-Uresti, 2016) reported Thalassinoides, Skolitos,