Ontogeny and autecology of an Early Cretaceous trigoniide bivalve from Neuquén Basin, Argentina

Understanding ontogenetic variation is fundamental for adequate species definition and is the key for recognizing evolutionary relevant processes like heterochrony or developmental constraints. The larval and post-larval shell ontogeny and the ecology of the trigoniide bivalve Myophorella garatei are described in this paper. The species occurs in offshore transition facies of the late Valanginian Pilmatué Member of the Agrio Formation in the Neuquén Basin, Argentina. The larval shell has a rather small prodissoconch I; and if prodissoconch II is present, it is rather weakly developed. From these data, a larval stage of low dispersal capability is inferred for Myophorella garatei, either short-lived planktotrophic or nonplanktotrophic. The study of post-larval development included general shell shape and ornamentation. To assess general shell shape a geometric morphometric analysis was performed on the lateral view, together with a study of allometry for the shell width. As a result, two main allometric stages of development could be identified. During the first stage a relative size reduction of the area co-occurs with a slight elongation of the shell, while the second stage is marked by dorsal bending of the shell and an increase on relative width. Ornamentation was examined qualitatively, but also a geometric morphometric analysis was performed on the flank costae. The first two flank costae are subconcentric; from the third costa onwards they become oblique, intially changing from more curved to less curved shapes, while on a third stage they show the opposite trend. Finally, a general interpretation of the adaptive morphology of adult shell was performed, concluding that M. garatei was adapted to low energy, soft bottom environments, and probably lived with the posterior straight margin levelled at the water-sediment interface.Facultad de Ciencias Naturales y Muse

Ontogeny and autecology of an Early Cretaceous trigoniide bivalve from Neuquén Basin, Argentina

Understanding ontogenetic variation is fundamental for adequate species definition and is the key for recognizing evolutionary relevant processes like heterochrony or developmental constraints. The larval and post-larval shell ontogeny and the ecology of the trigoniide bivalve Myophorella garatei are described in this paper. The species occurs in offshore transition facies of the late Valanginian Pilmatué Member of the Agrio Formation in the Neuquén Basin, Argentina. The larval shell has a rather small prodissoconch I; and if prodissoconch II is present, it is rather weakly developed. From these data, a larval stage of low dispersal capability is inferred for Myophorella garatei, either short-lived planktotrophic or nonplanktotrophic. The study of post-larval development included general shell shape and ornamentation. To assess general shell shape a geometric morphometric analysis was performed on the lateral view, together with a study of allometry for the shell width. As a result, two main allometric stages of development could be identified. During the first stage a relative size reduction of the area co-occurs with a slight elongation of the shell, while the second stage is marked by dorsal bending of the shell and an increase on relative width. Ornamentation was examined qualitatively, but also a geometric morphometric analysis was performed on the flank costae. The first two flank costae are subconcentric; from the third costa onwards they become oblique, intially changing from more curved to less curved shapes, while on a third stage they show the opposite trend. Finally, a general interpretation of the adaptive morphology of adult shell was performed, concluding that M. garatei was adapted to low energy, soft bottom environments, and probably lived with the posterior straight margin levelled at the water-sediment interface.Facultad de Ciencias Naturales y Muse

Ecological signature of the end-Triassic biotic crisis: what do bivalves have to say?

In order to understand the causes underlying the Triassic-Jurassic (T/J) mass extinction, we tested different bivalve features for extinction selectivity, i.e. shell mineralogy, age at the Rhaetian and three main autoecologic traits (feeding mechanism, tiering and motility/attachment). Also, diversity and turnover rates throughout the Triassic and the Early Jurassic were analysed in detail. The dataset employed for this analysis was a precise database at genus level including data from Induan to Sinemurian times. Results point to a true mass extinction for bivalves around the T/J boundary. This extinction was not ageselective at the boundary. Certain analyses suggested that shell mineralogy was a character significantly increasing survival odds, but this relationship seems to reflect selectivity on autoecologic traits. There was no difference in extinction proportions between both feeding types (i.e. deposit feeders and filter feeders); among the other traits, deep burrowers, epifaunal-motile and endobyssate forms seem to have been favoured, while shallow burrowers (and probably reclined forms) were more heavily affected. This pattern suggests an environmental stress at the boundary with some particular issues affecting the different life modes. Models linking magmatism in the Central Atlantic Magmatic Province with the end- Triassic mass extinction are a plausible scenario for this kind of perturbation

Palaeolatitudinal gradients along the southeastern Palaeopacific margin and the distribution of Early Jurassic bivalves

Presence-absence bivalve species data for each Early Jurassic stage along southeastern South America between 20 and 46°S present-day latitude were processed by a set of analytical methods to analyse the palaeolatitudinal patterns of diversity and distribution. The expected decrease in species diversity towards higher latitudes is punctuated by a consistent local diversity increase between 34 and 42°, especially evident during Pliensbachian and Toarcian times, which may be due to an abrupt change in palaeogeography at that latitude, coinciding with the Curicó direct connection to the open ocean and the establishment of an increased variety of habitats within the extensive Neuquén Basin. The proportions of systematic groups show relative increases towards both higher latitudes (Crassatelloidea, Nuculanoidea, Pectinoidea, Monotoidea, Inoceramoidea) and lower latitudes (Trigonioidea, Pholadomyoidea, Limoidea, Lucinoidea). Epifaunal bivalves were dominant during the Hettangian but by Pliensbachian-Toarcian times they were less common than infaunal ones, while semi-infaunal species had low diversities during the whole Early Jurassic. This study suggests that (a) large scale geographical conditions should be taken into account for the analysis of latitudinal diversity trends among benthonic faunas; and (b) latitudinal trends of some living bivalve lineages may have a longer and more complex history than previously thought.Fil: Damborenea, Susana Ester. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Departamento de Paleontología Invertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Echevarría, Javier. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleozoología Invertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentin

Paradigms in fight: laws, science and activism on the open world

Este artículo examina la dinámica del conocimiento científico en el siglo XXI y su relación al sistema legislativo y político. Se analizan brevemente los nuevos agentes en el entramado tecnocientífico como las revistas de impacto, los análisis bibliométricos y se propone que el movimiento conocido como open, abierto, es una reacción contra un entorno cerrado que se vuelve cada vez más contraproducente. Si bien hay instituciones de gran prestigio y asentadas en la comunidad científica que defienden los formatos abiertos, es clara la confrontación que se está produciendo entre conocimiento cerrado y abierto. El futuro resulta difícil de anticipar pero es claro que la retroalimentación entre privado y público es necesaria para el avance de la ciencia. El capitalismo salvaje en la ciencia supone un déficit de democracia para el ciudadano.This paper examines how scientific knowledge is affected in the 21th century, specially in relation to law and politics. The paper considers therefore new agents in that techno-scientific realm such as indexed journals, bibliometric analysis and proposes that open science movement is a reaction against a closed environment because of its counterproductivity. There are well known scientific institutions among scientists going open but it is clear the fight between closed and open science. Future is difficult to say but it is clear that a feedback between private and public is essential for scientific advancement. Turbo capitalism in science implies a lack of democracy for citizens