Rudist reef structure : Insights from orientation of hippuritids at l'Espà (Campanian, southern Pyrenees)

Altres ajuts: acords transformatius de la UABRudist were common Mesozoic reef builders, but rare examples exist to evaluate reef structure. The l'Espà locality (southern Pyrenees) is approached to study rudist reef structure by a quantitative assessment of the individuals' position (growing vs reworked) and its sedimentary context. This late Campanian reef is exposed along some 20 × 6 m outcrop. Builders are mainly Hippurites radiosus, although other rudists, such as Hippuritella lapeirousei, Hippuritella sp. and Mitrocaprina sp. are also present together with corals. The orientation of 325 specimens of mainly H. radiosus was plotted in stereographic and cartesian projections. Orientations and microfacies permit to differentiate 5 vertically stacked intervals (settings) along the outcrop: (1) Distal reef setting (reef-talus slope), with rudists reworked as large bunches of grouped specimens, with scarce erosion and preserving both valves articulated; (2) Halfway distal-proximal reef setting (close cluster reef), with abundant reworked, isolated, and flat-lying specimens. In this zone, endo-epibiont colonization on rudist shells is common, together with the presence of large (up to 1 m) branching and massive corals; (3) Proximal reef setting (frame/close cluster reef), where specimens are in life position; (4) A proximal back reef unit (spaced cluster reef) with few highly reworked specimens; (5) Distal back reef setting (very spaced cluster reef), with hardly any rudist fragments. This succession provides a reef tract model resembling that of most coral reefs and differs from smaller rudist reefs. The structure of the studied reef is well preserved as a result of high accommodation space related to thrust emplacement

A captorhinid-dominated assemblage from the palaeoequatorial Permian of Menorca (Balearic Islands, western Mediterranean)

Altres ajuts: CERCA Programme/Generalitat de CatalunyaMoradisaurine captorhinid eureptiles were a successful group of high-fibre herbivores that lived in the arid low latitudes of Pangaea during the Permian. Here we describe a palaeoassemblage from the Permian of Menorca (Balearic Islands, western Mediterranean), consisting of ichnites of small captorhinomorph eureptiles, probably moradisaurines (Hyloidichnus), and parareptiles (cf. Erpetopus), and bones of two different taxa of moradisaurines. The smallest of the two is not diagnostic beyond Moradisaurinae incertae sedis. The largest one, on the other hand, shows characters that are not present in any other known species of moradisaurine (densely ornamented maxillar teeth), and it is therefore described as Balearosaurus bombardensis gen. et sp. nov. Other remains found in the same outcrop are identified as cf. Balearosaurus bombardensis gen. et sp. nov., as they could also belong to the newly described taxon. This species is sister to the moradisaurine from the lower Permian of the neighbouring island of Mallorca, and is also closely related to the North American genus Rothianiscus. This makes it possible to suggest the hypothesis that the Variscan mountains, which separated North America from southern Europe during the Permian, were not a very important palaeobiogeographical barrier to the dispersion of moradisaurines. In fact, mapping all moradisaurine occurrences known so far, it is shown that their distribution area encompassed both sides of the Variscan mountains, essentially being restricted to the arid belt of palaeoequatorial Pangaea, where they probably outcompeted other herbivorous clades until they died out in the late Permian

Early-middle Permian ecosystems of equatorial Pangaea : Integrated multi-stratigraphic and palaeontological review of the Permian of Mallorca (Balearic Islands, western Mediterranean)

Altres ajuts: CERCA Programme/Generalitat de CatalunyaThe Cisuralian-Guadalupian (early-middle Permian) was a period of climate transition between the Carboniferous icehouse conditions to the latest Permian-Early Triassic hothouse. The landmasses had coalesced in the supercontinent Pangaea and the climate was progressively becoming more arid, especially in a belt over the palaeoequator. The deposits of present-day Mallorca (Balearic Islands, western Mediterranean) were located in those low palaeolatitudes, in the western margin of the Tethys Sea, and correspond to alluvial systems with meandering rivers. The present study divides the stratigraphic succession into three main units, formally described herein as the Bec de s'Àguila Formation, Port des Canonge Formation and Pedra de s'Ase Formation. Based on an exhaustive review of the literature and new magneto- and biostratigraphic data, the sequence has been dated between the early and middle Permian (Artinskian-Wordian). Moreover, the detailed study of the fossils has provided a complete account of the denizens of those ecosystems. Tetrapod tracks occur abundantly in the Port des Canonge Formation, with morphotypes attributed to moradisaurine captorhinid eureptiles, araeoscelidian diapsids/non-varanodontine varanopids, possible pareiasauromorph parareptiles, "pelycosaur"-grade synapsids and indeterminate synapsids. Spores and pollen grains from the Pedra de s'Ase Formation indicate an overall dominance of conifers, accompanied by sphenophytes, ferns and seed ferns. Overall, apart from providing the first detailed interpretation of the ecosystems of the Permian of Mallorca, these new data have made it possible to improve the characterisation of the Permian-Triassic tectonosedimentary cycle in the Balearic Islands, which contribute to the understanding of the evolution of the western peri-Tethys ecosystems