Roveacrínidos (Crinoidea: Roveacrinida) del Cenomaniano tardío al Turoniano temprano de Cerritos, oeste de la Plataforma Valles-San Luis Potosí, México / Roveacrinids (Crinoidea: Roveacrinida) from the late Cenomanian to early Turonian from Cerritos, western Valles-San Luis Potosí Platform, Mexico

Resumen Se estudiaron crinoideos roveacrínidos procedentes de afloramientos de la Formación Soyatal (Cenomaniano superior-Turoniano inferior) ubicados en la localidad de Cerritos (22º01'00" N -100º 57' 00" W) que se ubica en la parte occidental de la Plataforma valles-San Luis Potosí, México. Los roveacrínidos fueron identificados con las especies Roveacrinus geinitzi Schneider, 1989, Poecilocrinus dispandus elongatus Peck, 1943 y Roveacrinus sp. Estos microcrinoideos se estudiaron en secciones delgadas y están representados únicamente por fragmentos de las placas de la teca y de las braquiolas. Los roveacrínidos son organismos de formas oportunistas que se desarrollaron durante cambios del nivel del mar. Los roveacrínidos se encuentran asociados a un auge de calcispheras y a foraminíferos planctónicos de estrategia r y r-k como Muricohedbergella delrioensis (Carsey), M. planispira (Tappan), Heterohelix moremani (Cushman), Heterohelix reussi (Cushman), Whiteinella archaeocretacea Pessagno, W. aprica (Loeblich &Tappan), W. brittonensis (Loeblich & Tappan), W. baltica Douglas and Rankin, y W. paradubia (Sigal), lo cuales se consideran como indicadores de alta productividad primaria en un ambiente inestable que tuvo lugar durante la inundación de la Plataforma valles-San Luis Potosí en el límite Cenomaniano/Turoniano.

Abstract Fragments of roveacrinid crinoids of the upper Cenomanian-lower Turonian from Soyatal Formation located in the western part of the valles-San Luis Potosí Platform, Mexico, were studied. Roveacrinid fossils consist of small pieces of cup and brachials observed in thin sections that were identified with the species Roveacrinus geinitzi Schneider 1989, Poecilocrinus dispandus elongatus Peck 1943 and Roveacrinus sp. The Roveacrinids are opportunist organisms that developed during changes of sea level. The roveacrinids are associated with a calcispherids bloom and r and r-k strategy planktonic foraminifers, such as Muricohedbergella delrioensis (Carsey), M. planispira (Tappan), Heterohelix moremani (Cushman), Heterohelix reussi (Cushman), Whiteinella archaeocretacea Pessagno, W. aprica (Loeblich & Tappan), W. brittonensis (Loeblich &Tappan), W. balticaDouglas & Rankin, and W. paradubia (Sigal), which are considered as indicators of high primary productivity in an unstable environment that took place during the flooding of the valles-San Luis Potosí Platform in the Cenomanian/Turonian boundary. Rev. Biol. Trop. 63 (Suppl. 2): 17-25. Epub 2015 June 01.

Distributions and phylogeographic data of rheophilic freshwater fishes provide evidences on the geographic extension of a central-brazilian amazonian palaeoplateau in the area of the present day Pantanal Wetland

The analysis of the distribution patterns presented by examples of freshwater fishes restricted to headwater habitat: the anostomid Leporinus octomaculatus, the characins Jubiaba acanthogaster, Oligosarcus perdido, Moenkhausia cosmops, Knodus chapadae, Planaltina sp., the loricariid Hypostomus cochliodon, and the auchenipterid Centromochlus sp. provided evidences of a relatively recent shared history between the highlands of the upper rio Paraguay and adjoining upland drainage basins. Restricted to headwater of the uplands in the upper rio Paraguay and adjoining basins, these species provide biological evidence of the former extension of the central Brazilian plateau before the origin of the Pantanal Wetland. Disjunction took place due to an ecological barrier to these rheophilic taxa represented tectonic subsidence related to the origin of the Pantanal Wetland. Molecular analysis of Jubiaba acanthogaster revealed that the sample from the upper rio Xingu basin are the sister-group of a clade that includes samples from the upper rio Arinos (upper rio Tapajós) plus the upper rio Paraguay basin, supporting the assumption that the origin of the upper rio Paraguay basin causing vicariance between this basin and the upper rio Tapajós is the least vicariant event in the evolutionary history of the group.

A análise do padrão de distribuição apresentado por exemplos de peixes de água doce neotropicais restritos à habitats reofílicos de cabeceira: o anostomídeo Leporinus octomaculatus, os caracídeos Jubiaba acanthogaster, Oligosarcus perdido, Moenkhausia cosmops, Knodus chapadae, Planaltina sp., o loricariídeo Hypostomus cochliodon e o auquenipterídeo Centromochlus sp. fornecem evidências de uma história compartilhada relativamente recente entre as terras altas do alto rio Paraguai e bacias de terras altas vizinhas. Restritas às cabeceiras das áreas altas nas bacias do alto rio Paraguai e bacias vizinhas, estas espécies fornecem evidências biológicas da pretérita extensão do Planalto Central Brasileiro anteriormente a origem tectônica da planície alagável do Pantanal. Disjunções ocorreram devido a barreira ecológica para estes taxons reofílicos representada pela subsidência tectônica associada à origem do Pantanal. A análise molecular de Jupiaba acanthogaster revelou que amostras da bacia do alto rio Xingu consistem no grupo-irmão de um clado mais inclusivo que inclui amostras do alto rio Arinos (alto rio Tapajós) mais o alto rio Paraguai, suportando a suposição de que a origem do alto rio Paraguai causou vicariância entre esta bacia e o alto rio Tapajós no último evento vicariante na história evolutiva do grupo.

Arrhinolemur scalabrinii Ameghino, 1898, of the late Miocene: a taxonomic journey from the Mammalia to the Anostomidae (Ostariophysi: Characiformes)

The fossil species Arrhinolemur scalabrinii, which was described from late Miocene deposits of Entre Ríos, Argentina, is reevaluated. Whereas the species was originally placed in the Primates (Mammalia) and later made the unique member of the order Arrhinolemuroidea within the Mammalia, our analysis indicates that the specimen is rather a fish of the genus Leporinus, family Anostomidae (Characiformes). The species is redescribed, and the characters that support its new generic assignment are discussed.

A espécie fóssil Arrhinolemur scalabrinii, descrita de depósitos do Mioceno Superior de Entre Ríos, Argentina, é reavaliada. Apesar da espécie ter sido originalmente incluída em Primata (Mammalia), constituindo-se posteriormente no único membro da ordem Arrhinolemuroidea dentro de Mammalia, nossa análise indica que o espécime trata-se de um peixe do gênero Leporinus, família Anostomidae (Characiformes). A espécie é redescrita, e os caracteres que fundamentam a nova posição do gênero são discutidos.

An exceptionally preserved myodocopid ostracod from the Silurian of Herefordshire, UK.

An exceptionally preserved new ostracod crustacean from the Silurian of Herefordshire, UK, represents only the third fully documented Palaeozoic ostracod with soft-part preservation. Appendages, gills, gut system, lateral compound eyes and even a medial eye with a Bellonci organ are preserved, allowing assignment of the fossil to a new genus and species of cylindroleberidid myodocope (Myodocopida, Cylindroleberididae). The Bellonci organ is recorded for the first time in fossil ostracods. The find also represents a rare occurrence of gills in fossil ostracods and confirms the earliest direct evidence of a respiratory-cum-circulatory system in the group. The species demonstrates remarkably conserved morphology within myodocopes over a period of 425 Myr. Its shell morphology more closely resembles several families of myodocopes other than the Cylindroleberididae, especially the Cypridinidae and Sarsiellidae, thus questioning the utility of the carapace alone in establishing the affinity of fossil ostracods.

A mammalian lost world in southwest Europe during the late Pliocene.

BACKGROUND: Over the last decades, there has been an increasing interest on the chronology, distribution and mammal taxonomy (including hominins) related with the faunal turnovers that took place around the Pliocene-Pleistocene transition [ca. 1.8 mega-annum (Ma)] in Europe. However, these turnovers are not fully understood due to: the precarious nature of the period's fossil record; the "non-coexistence" in this record of many of the species involved; and the enormous geographical area encompassed. This palaeontological information gap can now be in part bridged with data from the Fonelas P-1 site (Granada, Spain), whose faunal composition and late Upper Pliocene date shed light on some of the problems concerning the timing and geography of the dispersals. METHODOLOGY/PRINCIPAL FINDINGS: This rich fossil site yielded 32 species of mammals, among which autochthonous species of the European Upper Villafranchian coexist with canids (Canis), ovibovines (Praeovibos) and giraffids (Mitilanotherium) from Asia. Typical African species, such as the brown hyena (Hyaena brunnea) and the bush pig (Potamochoerus) are also present. CONCLUSIONS/SIGNIFICANCE: This assemblage is taxonomically and palaeobiogeographically unique, and suggests that fewer dispersal events than was previously thought (possibly only one close to 2.0 Ma) are responsible for the changes seen around 1.9-1.7 Ma ago in the fauna of the two continents.

Biotic transitions in global marine diversity.

Long-term transitions in the composition of Earth's marine biota during the Phanerozoic have historically been explained in two different ways. One view is that they were mediated through biotic interactions among organisms played out over geologic time. The other is that mass extinctions transcended any such interactions and governed diversity over the long term by resetting the relative diversities of higher taxa. However, a growing body of evidence suggests that macroevolutionary processes effecting biotic transitions during background times were not fundamentally different from those operating during mass extinctions. Physical perturbations at many geographic scales combined to produce the long-term trajectory of Phanerozoic diversity.

Comparative diversification dynamics among palaeocontinents during the Ordovician Radiation.

The Ordovician Radiation was among the most extensive intervals of diversification in the history of life. However, a delineation of the proximal cause(s) of the Radiation remains elusive. Any such determination should involve an analysis of geographic overprints on diversification: did the Radiation occur randomly around the world or, alternatively, was it focused in particular geographic or depositional regimes? Here, I present a comparative evaluation of Ordovician diversification among several palaeocontinents to determine whether biotas associated with certain palaeocontinents exhibited different diversification patterns than others; in part, this involves a numerical "correction" to raw diversity trajectories. Clear disparities among palaeocontinents are indicated by the data, which appear to reflect differences in the extent of siliciclastic input partly in association with tectonic activity. Further testing will be required to fully substantiate the implication that siliciclastic influx was a predominant factor in the Ordovician Radiation, affecting a variety of higher taxa among all three Phanerozoic evolutionary faunas.

Calibrating the Ordovician Radiation of marine life: implications for Phanerozoic diversity trends.

It has long been suspected that trends in global marine biodiversity calibrated for the Phanerozoic may be affected by sampling problems. However, this possibility has not been evaluated definitively, and raw diversity trends are generally accepted at face value in macroevolutionary investigations. Here, we analyze a global-scale sample of fossil occurrences that allows us to determine directly the effects of sample size on the calibration of what is generally thought to be among the most significant global biodiversity increases in the history of life: the Ordovician Radiation. Utilizing a composite database that includes trilobites, brachiopods, and three classes of molluscs, we conduct rarefaction analyses to demonstrate that the diversification trajectory for the Radiation was considerably different than suggested by raw diversity time-series. Our analyses suggest that a substantial portion of the increase recognized in raw diversity depictions for the last three Ordovician epochs (the Llandeilian, Caradocian, and Ashgillian) is a consequence of increased sample size of the preserved and catalogued fossil record. We also use biometric data for a global sample of Ordovician trilobites, along with methods of measuring morphological diversity that are not biased by sample size, to show that morphological diversification in this major clade had leveled off by the Llanvirnian. The discordance between raw diversity depictions and more robust taxonomic and morphological diversity metrics suggests that sampling effects may strongly influence our perception of biodiversity trends throughout the Phanerozoic.

Analysis of the dental morphology of Plio-Pleistocene hominids. IV. Mandibular postcanine root morphology.

The subocclusal morphology of 168 permanent mandibular premolars (N = 77) and molars (N = 91) of Plio-Pleistocene hominids has been investigated. The taxonomic allocation of the teeth, which represent at least 46 individuals, was based on nondental evidence. Specimens were allocated to one of two major taxonomic categories, (EAFROB or EAFHOM), East African Homo erectus (EAFHER), or their taxonomic affinity was regarded as 'unknown' (N = 17). Information about the root system was derived from radiography and direct observation. Morphometric data were in the form of nine linear and two angular measurements based on eighteen reference points. Root form was also assessed using a scheme which recognised four classes of root morphology. Data were compared using both univariate and multivariate techniques, including Principal Component and Canonical Variate analysis. Posterior probabilities derived from the latter were used (in a two-taxon design model) to assess the affinities of the 'unknown' specimens. The variation in hominid mandibular premolar root form was interpreted as two morphoclines, based on the presumed primitive condition of the P3 (with mesiobuccal and distal roots, 2R: MB and D) and P4 (with mesial and distal root, 2R: M and D) root systems. One trend apparently leads towards root reduction (i.e. P3 = 1 R; P4 = 1 R), and the other to root elaboration (i.e. P3 and P4 = 2R: M and D). The extreme form of the latter is the 'molarisation' of the premolar roots seen in EAFROB. Despite major differences in root form there was relatively little taxonomic variation in root metrics, except for a more robust distal root system in EAFROB. Molar root form showed little interspecific variation except for M2 in which the roots in EAFROB were larger and more robust, with differences in root height being greater for the distal than for the mesial roots. Root form and metrics enable four of the 'unknown' specimens (KMN-ER 819, 1482, 1483 and 1801) to be tentatively allocated to EAFHOM, and a single specimen, KMN-ER 3731, to EAFROB. Published assessments of the root morphology of the 'robust' australopithecines from Swartkrans suggest that the premolar root form of Australopithecus (Paranthropus) robustus is not obviously intermediate between the presumed ancestral condition, and the 'molarised' mandibular premolar root systems of Australopithecus (Paranthropus) boisei.