Pedro García-Barrera

Maastrichtian crustacea (Brachyura : Decapoda) from the Ocozocuautla Formation in Chiapas, southeast Mexico

Abstract More than thirty complete specimens of Carcineretes planetarius Vega, Feldmann, Ocampo, and Pope, 1997, a member of the extinct decapod family Carcineretidae, have been collected from the upper part of the Ocozocuautla Formation in Chiapas, southeast Mexico. Stratigraphic occurrences of Carcineretes in the Caribbean Province suggest that this crab should be regarded as an index fossil for the early Maastrichtian. Six samples of this species may represent individuals that died during molting. The sudden disappearance of this family at the end of the Maastrichtian and its restricted paleobiogeographic distribution in the vicinity of the impact site suggest that the Carcineretidae may have been affected by the Chicxulub impact. Other decapod specimens collected from the same localities were assigned to the Xanthidae; Parazanthopsis meyapaquensis new genus and species, and Megaxantho zoque, new genus and species, are described. They constitute the second and third reports of Cretaceous xanthid crabs from Mexico. A lagoonal paleoenvironment is suggested, based on associated fauna and flora. Occurrences of index species of benthic and planktic foraminifera along with that of diagnostic rudist species confirm an early Maastrichtian age.

A new species of Meyeria (Decapoda: Mecochiridae) from the San Juan Raya Formation (Aptian: Cretaceous), Puebla State, Mexico

eurypterid from the Old Red Sandstone of Scotland. Palaeontology, 5:137-148. 1979. Problems of functional morphology and classification in stylonuroid eurypterids (Chelicerata, Merostomata), with observations of the Scottish Silurian Stylonuroidea. Transactions of the Royal Society of Edinburgh, 70:251-322. . 1985. Cyrtoctenus wittebergensis sp. nov. (Chelicerata: Eurypl e Sa dstone of Scotland. Palaeontology, terida), a large sweep feeder from the Carboniferous of South Africa. Transactions of the Royal Society of Edinburgh, 76:339-358. WOODWARD, H. 1866-1878. Monograph ofthe British fossil Crustacea elonging to the order Merostomata. Palaeontographical Society, London, 263 p.

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.

Lower Aptian AmmonitinaPseudohaploceras liptoviense (Zeuschner) in the Cumburindio Formation (Southwestern Mexico)

Abstract The presence of Pseudohaploceras liptoviense ( Zeuschner ) associated to Palorbitolina lenticularis ( Blumenbach )permits to interpret an Early Aptian age for the middle part of the lower member of the Cumburindio Formation nearby Turitzio (Michoacan). It is proposed that Boses species “Desmoceras” aguilerae, “D.” alzatei, “D.” burckhardti, “D.” durangense, “D.” tenuicostatum and “D.” wielandi are younger synonymous of Pseudohaploceras liptoviense ( Zeuschner ). An alternative interpretation as Mexican colonizers very close to Pseudohaploceras liptoviense ( Zeuschner ) cannot be conclusively disregarded.

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.

Fossil Ophiuroids of Mexico

Here we present an up to date study on fossil ophiuroids from Mexico. The specimens come from the following States within the Mexican Republic: Baja California Sur, Chiapas, Chihuahua, Coahuila, Oaxaca and Puebla. The total number of specimens is 20 and one ophiuroid bed that bears many specimens. The ophiuroids have been collected in rocks from upper Paleozoic age (Pennsylvanian) to Pliocene. Almost all specimens are well preserved and with the aid of several techniques such as X rays and detailed images taken from SEM, they are being described. We have recognized two families and four genera all belonging to the order Ophiurida. A new species will soon be published in a research paper.

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.