Jose Maria Pons

A New Early Campanian Rudist Fauna from San Luis Potosi in Mexico and its Taxonomic and Stratigraphic Significance

Abstract A rudist fauna composed of the radiolitids Potosites tristantorresi new genus, new species and Radiolites acutocostata (Adkins), the hippuritids Barrettia cf. ruseae Chubb, Torreites sanchezi (Douvillé), and Vaccinites vermunti Mac Gillavry, plagioptychids, and antillocaprinids is described from a rudist limestone succession in the central Mexican State of San Luis Potosí. The previously known species, one radiolitid from Texas and three hippuritids from the Caribbean Biogeographic Province, indicate the early Campanian. The new genus is a large radiolitid with a coiled and canaliculated left valve. New observations on R. acutocostata and V. vermunti shell morphology and variability are provided. Observations made on well preserved specimens of the latter species clarify the outer shell layer structure of the hippuritids right valve and has taxonomic implications. This is the first report of genus Torreites in Mexico and one of the northernmost records of genus Barrettia, already reported in southern Mexico from Chiapas State. This rudist limestone succession (informally ‘Temazcal limestones’ herein) is an easy-to-recognize cartographical unit; up to now it and Santonian and Turonian units have been mapped as the El Abra Formation in most available geological maps. Recognition of the successive carbonate platform intervals, between El Abra and Cardenas formations, improves the geological mapping and the understanding of the Mexican Gulf western margin evolution during the Late Cretaceous.

Albian Eoradiolites (Bivalvia: Radiolitidae) from Jabal Naïmia, Gafsa Region, Tunisia, with Revisional Studies on the Albian Forms of the Genus

Abstract The external morphology and its variability, myocardinal apparatus, and shell structure of both valves of the radiolitid rudist Eoradiolites plicatus (Conrad) are described, based on the examination of about one hundred well-preserved, fairly complete specimens that are free of sediment matrix, found in a single bed of an ammonite-bearing Albian succession (‘Knemiceras beds’, Zebbag Formation) in central Tunisia. This study provides the most nearly complete knowledge of any Eoradiolites species to date. With this background, all previous records of E. plicatus, as well as the taxonomic status of the other Albian species of the genus, are revised considering both original material, when available, and published papers. As a result, the systematics of Eoradiolites is simplified.

Campanian rudists (Hippuritida, Bivalvia) from Costa Rica (Central America)

Abstract The Campanian rudist fauna identified from the localities Playa Panamá, Santa Rosa National Park, Colorado de Abangares, and Bolsón in Guanacaste Province, Costa Rica, is composed of the antillocaprinids Antillocaprina sp. aff. A. suboccidentalis Chubb, 1967, Antillocaprina sp. and Antillocaprinidae indet.; the multiplefold hippuritids Barrettia monilifera Woodward, 1862, Parastroma trechmanni Chubb, 1967, and cf. Whitfieldiella gigas (Chubb, 1955); the plagioptychids Plagioptychus trechmanni Chubb, 1956, Plagioptychus sp. cf. P. zansi Chubb, 1956, Mitrocaprina costaricaensis new species, Mitrocaprina multicanaliculata Chubb, 1956, and Plagioptychidae indet.; and the radiolitids Radiolites sp. aff. R. multicostata (Adkins, 1930), Alencasterites new genus mooretownensis (Trechmann, 1924), Bournonia? tetrahedron (Chubb, 1967), Chiapasella sp., Guanacastea costaricaensis new genus new species, cf. Potosites sp. aff. P. tristantorresi Alencáster and Pons in Pons et al., 2010, and aff. Thyrastylon sp. Although some differences in rudist diversity and sedimentary setting were observed among localities, most species indicate the same age for all occurrences, which correspond to the Campanian, probably mid-Campanian. Radiolitid specimens appear better preserved than those of other taxa and are thus discussed more in detail. Both the number of radiolitid genera exclusively known from the New World, and reasonable doubts about the correct attribution of some New World species to Old World genera, indicate important differences between rudist faunas at both sides of the Atlantic (Mediterranean and American Tethys, respectively) during the Late Cretaceous.

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.

Undescribed Ichthyosarcolitesfrom Sicily, belonging to Gemmellaro's collection

Abstract Undescribed rudist specimens from Gemmellaros collection, housed in the Palaeontological Museumof the University of Palermo, and labelled as Ichthyosarcolites anguiformis Gemmellaro , have been identified as I. monocarinatus Sliskovic . The description of these specimens, facilitated by their good preservation, has resulted in a better knowledge of the shell features of this species and as a consequence of the genus Ichthyosarcolites .

Systematic and Biostratigraphic Significance of the American Rudist Bivalve Durania aguilae Adkins, 1930

Abstract The rudist bivalve Durania aguilae Adkins was described from the Mendez Formation in Mexico and originally attributed to the Santonian. We revise this species and show that it belongs to the genus Chiapasella Müllerried. We also recognize that Chiapasella aguilae (Adkins) is a senior synonym of Chiapasella trechmanni Mitchell and Gunter, an important biostratigraphic indicator in the late late Maastrichtian of Jamaica. Chiapasella aguilae is therefore an important late late Maastrichtian marker fossil that has been recorded from Jamaica, Mexico, and Cuba.

The Rudist Bournonia mutabilis (Stoliczka, 1871) redescription based on new material from the Ottakkovil Formation (Maastrichtian), Ariyalur region, South India

The argillaceous sandstones of the Ottakkovil Formation, dated as Early-Upper Maastrichtian (Pachydiscus otacodensis Zone) yield a diversified fauna of echinoids, gastropods, ammonites, oysters and rudists. The study of these rudists belonging to the species Bournonia mutabilis allowed to complete the only existing description and figures given by Stoliczka 1871 and to confirm, by means of the shell structure analysis, its attribution to the genus Bournonia and not to Durania as it has been recently suggested by some authors.

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

Abstract. Plagioptychids are a conspicuous, although minor, component in uppermost Cretaceous rudist-bearing outcrops of the Caribbean Province, where other rudist families are more abundant and diverse. In the Chiapas Central Depression, the plagioptychid rudist fauna includes the following taxa: Plagioptychus antillarum (Douvillé) and Mitrocaprina sp. from the middle Campanian Suchiapa Formation, Plagioptychus muellerriedi Alencáster from the early Maastrichtian Ocozocoautla Formation, and Plagioptychus fragilis Chubb and Mitrocaprina tschoppi (Palmer) from the late Maastrichtian Angostura Formation. These five species are described in detail and some probable synonymies are discussed. Analysis of the literature on American plagioptychids reveals that the characters of too many taxa are still insufficiently known to attempt any thorough phylogenetic analysis. Other lines of evidence also seem to indicate that American Plagioptychidae diversity is probably higher than recognized today, which might result in a more significant difference to Plagioptychidae of the Mediterranean Tethys.