The rudist fauna of the Cárdenas Formation, Maastrichtian, San Luis Potosí State, Mexico

Abstract

A Maastrichtian rudist fauna composed of the radiolitids Biradiolites aguilerae Böse, B. Cárdenasensis Böse, Huasteca ojanchalensis (Myers), Tampsia floriformis Myers, and Trechmannites rudissimus (Trechmann), the hippuritids Caribbea muellerriedi (Vermunt) and Praebarrettia sparcilirata (Whitfield) sensu lato, and the plagioptychids Coralliochama gbohemi Böse and Mitrocaprina tschoppi (Palmer) is described from the Cárdenas Formation in San Luis Potosí State, Mexico. Abundant fossil material and excellent preservation of a number of specimens allowed observation of both the internal and external shell characters and their ontogenetic and eco-phenotypic variability. The description of some hitherto insufficiently known species has been enhanced and/or completed, making easier their subsequent identification and allowing their unequivocal generic assignation. Two new genera, Huasteca and Trechmannites, are proposed for two already known species of radiolitids. The Cárdenas Formation exhibits a continuously exposed sequence in the vicinity of Cárdenas. Thus, precise stratigraphic location of all fossil localities and their rudist associations, ranging from the early to the early late Maastrichtian, has been possible.

Marginal marine trace fossils from the Cárdenas Formation (Maastrichtian), Rayón municipality, San Luis Potosí, Central Mexico

“…Sources of sediment for the Cárdenas Formation were located to the west and northwest, the sediments filled an elongated shallow basin that was bordered to the east by a barrier that represented the beginning of folding and uplift of the Sierra Madre Oriental during the initial Laramide pulsations (Vega et al, 1995). The physical characteristics of the rocks as well as low fragmentation of the rudist association (Schafhauser et al, 2003;Oviedo-García, 2005;Pons et al, 2013) at Amoladeras suggest subtidal and lagoon conditions, with low to moderate energy and soft substrates. This is congruent with the trace fossils identified in the present study, represented by Diplocraterium parallelum, Ophiomorpha nodosa, Skolithos linearis, and Palaeophycus tubularis.…”

“…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, 2008Omaña et al, , 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, and Ophiomorpha from La Calzada locality, Ciudad del Maíz Municipality, San Luis Potosí State.…”

Campanian and Maastrichtian plagioptychid rudists (Hippuritida, Bivalvia) of the Chiapas Central Depression, southern Mexico

“…Recent taxonomic papers on American Late Cretaceous rudist faunas (Pons et al, 2010, 2013, 2016b), besides the proposal of new plagioptychid taxa, reported other taxa in open nomenclature owing to the lack of diagnostic characters. Nevertheless, some of the characters illustrated by these indeterminate taxa suggest they cannot be ascribed to any of the known genera.…”

“…Angostura Formation, late Maastrichtian, from the Chiapas Central Depression, Mexico. Besides the type locality and Santa Clara (Thiadens, 1936; MacGillavry, 1937) occurrences in Cuba, the species has been reported from the Maastrichtian Guinea Corn Formation in Coffee Piece, Grantham, Jamaica (Mitchell and Gunter, 2004) and the Maastrichtian Cárdenas Formation in Cárdenas, San Luis Potosí, Mexico (Pons et al, 2013).…”

Campanian and Maastrichtian hippuritid rudists (Hippuritida, Bivalvia) of the Chiapas Central Depression (southern Mexico) and implications for American multiple-fold hippuritid taxonomy

“…Van Dommelen (1971) remarked about the absence of canals in the ISL of the LV and the furrows at the outer surface of the LV, beside the development of the rays in the RV and the relative location of the myocardinal elements. Grubić (2004) considered as relevant the presence of a particular capillary structure in the OSL of the RV; this character was described and morphostructurally reinterpreted by Pons et al (2013) as a noncompact hippuritid shell structure and is herein considered a diagnostic character of the genus. Götz and Mitchell (2009) proposed the genus Laluzia Götz and Mitchell, 2009 (type species L. armini Götz and Mitchell, 2009) for specimens from the Cárdenas Formation, San Luis Potosí, Mexico.…”