Révision systématiquedu genre Sphenorhynchia Buckman, 1918 (Brachiopoda,rhynchonellidae): Implications taxonomiques, évolution,biostratigraphie

A lot of numerous rhynchonellid shells referedto the main species of genus SphenorhynchiaBuckman have been sampled in stratigraphically well-defined beds of Dogger period in the Mâconnais and in the Jura (France). Here, morphologic and anatomic characters and variability of S. plicatella, S. matisconensis, S. bugeysiaca, S. ferryi and S. dominula are studied.The main interest of this revision is to establish a complete diagnosis of the genus, not studied since its creation in 1918, with very limited knowledge of the internal structures. The settlement of this diagnosis is based on the type-species, S. plicatella, sometimes a little «unconventional form (beak, outline of the young shells, orientation of dental lamellae, delthyrial cavity), and also on the other species' characters. So, I expect that a later diagnosis will be avoided.Other advantages are observations on the taxonomic place of Sphenorhynchia in the RhynchonellidaeGray (in the TetrarhynchiinaeAger rather than in the CyclothyridinaeMakridin), on its evolution in the course of the Dogger period and the establishment of the biostratigraphy of its main species.     

Comparaison entre des Crustacésa Céphalon isolé, a propos d'un beau matériel de syncarides du paléozoïque implications phylogéniques

Are the Eumalacostraca issued from a model of Crustacea which the carapace would have disapeared later on in some of them, and persisted in others, or from one without carapace that some of its decendants would have acquired? In the two instances this ancestor would goes far back, seeing that, already, in the Devonian, Syncarida, Stomatopoda, Phyllocarida and Eocarida were differenciated. With regard to the preliminary survey on a fine material of Syncarida from the Stephanian of the region of Autun, comparisons between two models of Crustaceans from which the cephalon includes only sensorial and gnathal segments, without adjunction of any thoracic metamere, allow to specify the notion of carapace, and to surround the question. The great oldness of the origin of the phyla possessing or not possessing a carapace seems to exclude the hypothesis of a passing over from one model to the other and suggests a representation of the common ancestor which have to be searched in the Cambrian period.     

Révision systématiquedu genre Steginoporella smitt, 1873 (Bryozoa Cheilostomata)

Systematic revision of the genus Steginoporella: until now about eighty species were described. Only twenty recent species and thirty-four fossil ones are maintained. Several species and subspecies are new.The main interest of this revision is to establish a biostratigraphical scale: the settlement of this scale is based on the known stratigraphical distribution and on an attempt of phylogeny.The second advantage is ecological: all recent species live in marine tropical environment. The Steginoporella are good paleoecological indicators.At last, the establishment of a paleobiogeography, even incomplete and not definitive, allows to understand more easily recent distribution of Steginoporella connected with the great events of earth evolution.     

Paléobiogéographie de quelques Stephanocerataceae (Ammonitina) du Jurassique moyen et supérieur; une confrontation avec la théorie mobiliste

From Bajocian to lower Kimmeridgian, the subfamilyStephanocerataceae represents a large stock of the ammonite fauna. Though it is tributary of author's stratigraphical correlations and systematical interpretations, its geographical distribution with a drifting continents concept gives many teaching about the study of this superfamily, the continental drift and its consequences. Showing a world wide repartition at its apparition this stock then presents branches; the one (Stephanoceratidae) is not envisaged here; the second (Sphaeroceratidae and Cardioceratidae families) characterises rather the «boreal province; the third (Macrocephalitidae family) is chiefly specific of the «tethysian province. A «north-east pacific province with boreal affinities and a «south-east province with tethysian affinities are delimited. It is probably from its fauna that the tethysian macrocephalitid stock appears; first represented by ammonites specifically north american in middle and upper Bathonian stage, they extend during upper Bathonian and lower Callovian and reach South America and the Tethys. The presence of a narrow sea, on Patagonia, West Antarctica, East Africa, Madagascar and India, joining the Tethys and the south edge of Gondwania, is proved at various times, at Bajocian and Callovian stages.     

Continental gateways and the dynamics of mammalian faunas

Continental gateways occur where mountainous topography interacts with changing climate and sea level to open or close dispersal corridors. The interaction of permeable or impermeable montane barriers with changing or stable climate yields four biogeographic states, each associated with changes in diversification rates and ecological structure of faunas. For example, permeable montane barriers and climatic stability result in low rates of immigration and extinction, elevated endemic speciation, and stable ecological structure. Three examples from the mammalian fossil record test these scenarios. (1) In Miocene faunas of Pakistan, immigration rates peaked and faunal proportions changed during an interval of cooling and open corridors. (2) In Miocene faunas of Spain, elevated extinction and origination rates and changing trophic structure occurred during regional aridification with open corridors. (3) In Quaternary faunas of South Africa, ungulates experienced range reductions and elevated extinction during the transition from glacial to interglacial climates as corridors closed.     

Early tetrapodomorph biogeography: Controlling for fossil record bias in macroevolutionary analyses

The fossil record provides direct empirical data for understanding macroevolutionary patterns and processes. Inherent biases in the fossil record are well known to confound analyses of this data. Sampling bias proxies have been used as covariates in regression models to test for such biases. Proxies, such as formation count, are associated with paleobiodiversity, but are insufficient for explaining species dispersal owing to a lack of geographic context. Here, we develop a sampling bias proxy that incorporates geographic information and test it with a case study on early tetrapodomorph biogeography. We use recently-developed Bayesian phylogeographic models and a new supertree of early tetrapodomorphs to estimate dispersal rates and ancestral habitat locations. We find strong evidence that geographic sampling bias explains supposed radiations in dispersal rate (potential adaptive radiations). Our study highlights the necessity of accounting for geographic sampling bias in macroevolutionary and phylogenetic analyses and provides an approach to test for its effect.     

Body-size trends of cyrtocrinids (Crinoidea,Cyrtocrinida)

Cyrtocrinids (Cyrtocrinida) are fully sessile post-Palaeozoic crinoids (Crinoidea) of unusual morphology exhibiting complex diversity dynamics and evolutionary history. To date, however, no study has ever examined the macro-evolutionary patterns of body-size trends in these crinoids. A compilation of a body-size dataset for cyrtocrinid genera revealed a trend of increasing size throughout their evolutionary history. A maximum-likelihood approach showed that the observed trend is best characterized by a general random walk. Recorded body-size pattern is thus consistent with the Cope-Depéret's rule implying the existence of active, directional selective pressures towards larger body-sizes. The case provides a rare example of directional body-size trend in the fossil record.     

Genetic determinism of parasitic circadian periodicity and subperiodicity in human lymphatic filariasis

The larval parasites of the pantropical lymphatic filariasis exhibit two types of circadian behaviour. Typically, they only appear in the human bloodstream at nighttime, synchronised with their mosquito vectors. In Polynesia and parts of Southeast Asia, free of nocturnal vectors, they are found at all hours, and each population biorhythm differs. Through a geometrical approach, we explain this circadian diversity by a single, dominant mutation: the clocks of individual parasites are set at midnight (ubiquitous) or at 2 p.m. Compared to other circadian genes, this mutation must be very old, as it is shared by four biologically remote genera of parasites. This seniority sheds new light on several theoretical and practical aspects of vector-parasite temporal relations.     

Human development and log-periodic law

We suggest applying the log-periodic law formerly used to describe various crisis phenomena, in biology (evolutionary leaps), inorganic systems (earthquakes), societies and economy (economic crisis, market crashes) to the various steps of human ontogeny. We find a statistically significant agreement between this model and the data.     

Clutch size: a major sex ratio determinant in fig pollinating wasps?

Under local mate competition, sex ratio theory predicts that increasing numbers of ovipositing females (foundresses) on a site should lead to higher proportions of males in their broods. Fig pollinators have confirmed this prediction. It is also predicted that with decreasing clutch size, solitary foundresses should produce increasing proportions of sons. We show this to be true. Further, when several females compete, brood size decreases. As a result, the proportion of males increases, and this could provide a mechanistic explanation of sex ratio response to numbers of colonizing females. Therefore, sex ratio data on fig wasps need to be reassessed to determine whether females 'count' other foundresses, as is generally accepted, or whether they simply 'count' the number of eggs that they lay.