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In this study, we present apatite fission-track results obtained for ten rock samples collected from three different areas across the Sierra Madre del Sur, southern Mexico. The central objective of our study is the timing of the exhumation event that took place in southern Mexico during Late Cretaceous–Palaeogene time. The thermochronometric data obtained during this work indicate that a Late Cretaceous–Eocene cooling is recorded within the Sierra Madre del Sur, and this is interpreted as resulting from exhumation, an orogenic event that is contemporaneous with the Laramide sensu lato (or the Mexican Orogeny). The fission-track ages become younger from west to east across the Sierra Madre del Sur, whereas the cooling rates also increased in the same direction approximately during Campanian–middle Eocene time. Here, we suggest that the activity of the major fault systems of southern Mexico, such as the Caltepec and the Oaxaca faults, played a primary role in the development of geological structures and the exhumation of the Sierra Madre del Sur. Active magmatism during the evolution of the Mexican Orogen implicates the subducted Farallon slab as the main driver of crustal thickening. Moreover, the possible influence of the eastward movement of the Chortis Block on the deformation of the Sierra Madre del Sur cannot be ruled out. [ABSTRACT FROM AUTHOR]

This paper documents the occurrence of Skolithos linearis, Planolites beverleyensis, and Thalassinoides isp. in the Cárdenas Formation (Late Cretaceous), southeastern San Luis Potosí, central Mexico. This is the second record of S. linearis for this lithological unit, while P. beverleyensis and Thalassinoides isp. are documented for the very first time in this formation. The ichnoassemblage is referred to the Cruziana Ichnofacies which, in concert with associated invertebrate body fossils (Exogyra costata), suggest a shoreface setting with moderate- to low-energy conditions and episodic storms. [ABSTRACT FROM AUTHOR]

Summary: We describe two new fossil woods from the San Carlos Formation (Upper Cretaceous), Chihuahua State, Mexico. The first wood resembles the fossil genus Metcalfeoxylon in having solitary vessels, scalariform perforation plates, vessel-ray parenchyma pits of similar size as the intervessel pits, axial parenchyma apotracheal diffuse and diffuse in aggregates, and heterocellular multiseriate rays with long, uniseriate tails. The second wood is a new fossil genus, and it is characterized by having diffuse porous wood, vessels predominantly solitary, vessel outlines oval and tending to be of two diameter classes, simple perforation plates, minute alternate intervessel pits, vessel-ray parenchyma pits similar to intervessel pits in size and shape, vasicentric tracheids, non-septate fibers, homocellular rays, and exclusively uniseriate and biseriate rays. This combination of features supports its placement in Myrtales (?Myrtaceae), in a new fossil-genus named Lazarocardenasoxylon. These two new records provide more information about the floristic composition of the Late Cretaceous flora of the San Carlos Formation and its relationship with those from the southern USA. However, a definitive picture of the floristic relationship of these Cretaceous floras of northern Mexico and southern USA remains elusive. [ABSTRACT FROM AUTHOR]

The fossil fish Ptychodus Agassiz, 1834, characterized by a highly distinctive grinding dentition and an estimated gigantic body size (up to around 10 m), has remained one of the most enigmatic extinct elasmobranchs (i.e. sharks, skates and rays) for nearly two centuries. This widespread Cretaceous taxon is common in Albian to Campanian deposits from almost all continents. However, specimens mostly consist of isolated teeth or more or less complete dentitions, whereas cranial and post-cranial skeletal elements are very rare. Here we describe newly discovered material from the early Late Cretaceous of Mexico, including complete articulated specimens with preserved body outline, which reveals crucial information on the anatomy and systematic position of Ptychodus . Our phylogenetic and ecomorphological analyses indicate that ptychodontids were high-speed (tachypelagic) durophagous lamniforms (mackerel sharks), which occupied a specialized predatory niche previously unknown in fossil and extant elasmobranchs. Our results support the view that lamniforms were ecomorphologically highly diverse and represented the dominant group of sharks in Cretaceous marine ecosystems. Ptychodus may have fed predominantly on nektonic hard-shelled prey items such as ammonites and sea turtles rather than on benthic invertebrates, and its extinction during the Campanian, well before the end-Cretaceous crisis, might have been related to competition with emerging blunt-toothed globidensine and prognathodontine mosasaurs.

We report several raninoid specimens collected from the lower Maastrichtian Lower Siltstone Member of the Potrerillos Formation (Difunta Group), NE Mexico. These specimens were collected from fine-grained sandstones that crop out at the NE edge of the Parras Basin, Coahuila. This outcrop is very close to a structural feature that has been active since Late Jurassic times (San Marcos Fault) and has affected depositional lithostratigraphic units from the Upper Jurassic to Upper Cretaceous. The studied specimens are assigned to Bournelyreidus paredonensis n. sp. (Lyreididae Guinot, 1993) and Coahuilanina difuntaensis n. gen., n. sp. (Raninidae de haan, 1839). A new subfamily, Coahuilanininae is described to accommodate the new genus and species, Coahuilanina difuntaensis. The new frog crabs represent the first formally described raninoids from the lower Maastrichtian portion of Difunta Group, adding to an already diverse assemblage of raninoids from Mexico. • New taxa of crabs. • Upper Cretaceous. • NE Mexico. • Possible chemosynthetic communities. [ABSTRACT FROM AUTHOR]

The Mosasauridae underwent a major radiation early in the Late Cretaceous, with the subfamilies Plioplatecarpini and Tylosaurini appearing in the Turonian. Here we report an almost complete mosasaur skull assigned to the plioplatecarpine genus Yaguarasaurus. The specimen was discovered southwest of Vallecillo in the northeastern Mexico state of Nuevo Leon, about 80 km north of Monterrey, in a laminated limestone layer of the upper member of the Agua Nueva Formation (Upper Turonian - ?Lower Coniacian). The specimen is referred to as a new species, Y. regiomontanus. This is the first report of Yaguarasaurus from Mexico and the most complete of the Americas. At roughly 5 m in length, it is one of the earliest large mosasaurids. Along with Yaguarasaurus columbianus , Russellosaurus coheni , and an unnamed plioplatecarpine from Texas, it documents the rapid diversification and expansion of plioplatecarpines in the marine realm in the Turonian. • The Highlight of the paper is that is a new species of mosasaurus described for Mexico. [ABSTRACT FROM AUTHOR]

The record of land tetrapods of the Cerro del Pueblo Formation (Late Cretaceous, Campanian), in Coahuila, includes turtles, pterosaurs, dinosaurs, and crocodyliforms. This last group is represented only by goniopholidids, indeterminate eusuchians, and Brachychampsa montana. In this work we report the first crocodyliform remains from La Parrita locality, Cerro del Pueblo Formation, based on one isolated tooth, vertebrae, and osteoderms. The association of crocodyliforms, turtles, dinosaurs, and charophyte oogonia provide evidence for stagnant to fluvial environments on a delta plain with tropical climate for the Cerro del Pueblo Formation during the Late Cretaceous. [ABSTRACT FROM AUTHOR]

In the paleogeographic reconstruction of Mexico and northern Central America, an ever-increasing amount of evidence shows that the entire region is a collage of suspect terranes transported from abroad, whose timing and sense of motion are now beginning to be understood. Among these, the Chortis block (nuclear Central America) and the Baja California Peninsula have been proposed as pieces of continent separated from the Pacific coast of southwestern Mexico, that have moved either southeastward by the Farallon plate or northwestward by the Kula plate. Previous studies mainly confined to the northern margin of the Chortis block, confirmed a left-lateral displacement of 130 km in Neogene time. Further studies made northwestward along the Mexican coast provided a better understanding of magmatic and metamorphic processes in the area, and suggested times of detachment increased to 30 Ma, 40 Ma, and 66 Ma. The pre-detachment westernmost position of the block has changed, depending on the model chosen, from Puerto Vallarta and beyond, to the current position. Here we show that the isotopic mineral ages from coastal granites along the coast from Puerto Vallarta, Jalisco (80 Ma) to Puerto Angel, Oaxaca (11 Ma) record systematic decrease of cooling ages from NW to SE. This pattern is interpreted to result from the progressive uplift of rocks exposed at the present-day coast in that direction, such uplift occurred in response to the development of the Middle America Trench at the newly formed continental margin when the Chortis block was sliding at an average rate of 1.5 cm/year in a sinistral sense to its present position. Our results also constrain the position of the Kula-Farallon spreading axis north of Puerto Vallarta. These observations led us to conclude that several indicators point to this time and region for the onset of strike-slip drifting of the Chortis block toward its current position. Here, we also present several view points in terms of other possilble interpretations to different tectonic, geologic and isotopic data sets published recently by different authors. [ABSTRACT FROM AUTHOR]

The supposed vestige of a cephalopod gladius from Turonian platy limestones at Vallecillo, north-east Mexico, named Palaeoctopus pelagicus by Fuchs et al. in 2008, is reinterpreted and shown to be a gular plate of a coelacanth fish, possibly of the genus Megacoelacanthus. In addition to the gular plate, two extrascapulars and fin rays of all fins are preserved on one slab and its counterpart. This is the first record of a coelacanth from these lower Turonian strata at Vallecillo, which are rich in fish. [ABSTRACT FROM AUTHOR]

A new vertebrate fossil assemblage of Late Cretaceous age is reported here. This discovery represents the results of the 2007 and 2008 field seasons in the locality known as "Las Jicoteas" situated in the municipality of Ocampo, in northwestern Coahuila, Mexico. The stratigraphic sequence where this fossil fauna occurs can be correlated to the Lower Member of the continental Aguja Formation that outcrops in the neighbouring Big Bend region of Texas. This new fauna bears the first record of a nodosaur for Mexico, and, also additional dinosaur remains attributed to the families Tyrannosauridae and Hadrosauridae are recorded. Associated fossil taxa include lepisosteid fishes, turtles and crocodile remains. The palaeocological conditions inferred by this new faunal assemblage suggest a paralic system with prodelta, marshes, lagoons, and nearshore marine deposits. [ABSTRACT FROM AUTHOR]

Palaeoctopus pelagicus sp. nov. is described from the early Turonian Vallecillo Limestone in north-eastern Mexico. The species represents the first record of a fossil octopod from the Americas and the second species of the genus Palaeoctopus. The holotype and only known specimen preserves one half of an originally bipartite gladius vestige. Soft parts are not preserved. The gladius vestige is distinguished from P. newboldi from the Santonian Limestone of Lebanon by the arrangement of fields, striation and reinforcements. The new material supports previous ideas suggesting that the paired stylets of modern Octopoda evolved through gradual reduction of a Teudopsis-like gladius via a transitional stage similar to Palaeoctopus. The origin of Octopoda and Cirroctopoda likely dates back to a period between the Toarcian (180 Ma) and the early Turonian (93 Ma). Palaeoecological conditions in the Vallecillo ocean suggest that P. pelagicus sp. nov. inhabited the pelagic shelf. Hostile low oxygen conditions on the sea floor exclude a benthic mode of life for P. pelagicus sp. nov. [ABSTRACT FROM AUTHOR]

Abstract: The ‘Plattenkalk’ of Vallecillo, approximately 100km north of Monterrey in north-eastern Mexico, has yielded an ammonite assemblage of both North American (Western Interior) and Tethyan elements, comprising Tragodesmoceras bassi Morrow, Quitmaniceras reaseri Powell, Watinoceras coloradoense (Henderson), Pseudaspidoceras pseudonodosoides (Choffat), P. flexuosum Powell, Mammites nodosoides (Schlüter), Vascoceras birchbyi Cobban and Scott, Fagesia catinus (Mantell), F. superstes (Kossmat), and a few indeterminate forms. The excellent preservation of the shells, for instance of apertures, stomach contents or spines joined to the body chambers of P. flexuosum, as well as the occasional presence of aptychi, indicate rapid burial shortly after death. Correlation with the Cenomanian–Turonian boundary GSSP at Pueblo, Colorado, indicates continuous deposition from the latest Cenomanian to the early Turonian at Vallecillo. The index species P. flexuosum shows a diachronous first appearance datum between the two sections. [Copyright &y& Elsevier]

Aim To analyse the worldwide distribution patterns of Turonian marine biotas using a panbiogeographical approach. Location Turonian localities of southern and north-eastern Brazil, Mexico, Canada, central Europe, England and Morocco. Method Panbiogeographical track analysis. Results Nine generalized tracks and six nodes were found. The generalized tracks comprise two vicariant track patterns (one northern and one mid-southern) across the Atlantic. Main conclusions The generalized tracks show clearly two separate marine biotas, which were associated with the proto-South Atlantic and the proto-North Atlantic oceans. These generalized tracks, as well as the two vicariant track clusters between the north and south Atlantic, are identified by vicariant relationships shared by most of the taxa analysed, and illustrate the final break up of the Gondwana and Laurasia supercontinents and the consequences of vicariant events for the biogeography of the Atlantic Ocean. [ABSTRACT FROM AUTHOR]

A new fossil needlefish species is named in this work as Hastichthys totonacus, based on specimens from the marine Turonian deposits of the Agua Nueva Formation, exposed in the Huehuetla quarry, into the Sierra Norte region of Puebla, Mexico. The osteology of this new species shows a diagnostic character of the order Aulopiformes, the occurrence of epipleurals bones associated with abdominal centra, at least from the centrum 2. This new species also shows the most distinctive features of the family Dercetidae and genus Hastichthys , including the longirostrine head; the elongated body; two pairs of triangular and expanded transverse processes in the abdominal centra; the low and elongated neural arches on abdominal centra bearing short neural spines; a row of triradiate scutes on each body flak; and the anterior part of maxilla and dentary bones are ornamented with longitudinal and parallel ridges. Hastichthys totonacus is the second species in the genus and differs from the type species, H. gracilis , in having a relatively shorter body with 59 total centra, the head length is about 38% of the standard length, the dorsal fin has seven rays, and the anal fin has eight rays. The inclusion of this new species in different phylogenetic analyses reveals that the interrelationships of the Dercetidae family are poorly resolved and that H. totonacus sp. nov. and H. gracilis form a monophyletic group. Additionally, the species Rhynchodercetis regio, from the Turonian sediments of the Agua Nueva Formation, exploited in the Vallecillo quarry, Nuevo León, northern Mexico, is also placed into the genus Hastichthys because it has the most prominent character of this genus, the tips of rostrum and mandible are ornamented with longitudinal and parallel striae and ridges. The occurrence of these two Mexican Turonian species extends the temporal and geographical distribution of the genus Hastichthys , from the Cenomanian deposits of the western Tethys Sea realm preserved in the Middle East toward the Turonian deposits of eastern Mexico, at the southern end of North America. • Dercetidae is a fossil family with poor records in the southern end of North America. • The description of Hastichthys totonacus brings new light in the understanding of the diversification of Dercetidae. • Rhynchodercetis regio is placed in the genus Hastichthys. • The phylogenetic hypothesis of Enchodontoidei requires a comprehensive reassessment. [ABSTRACT FROM AUTHOR]