The Middle Permian-Late Permian boundary (Guadalupian-Lopingian boundary, GLB) interval is characterised by important faunal assemblage changes. This extinction-turnover episode is considered by some authors to be the first step of the end-Permian biodiversity drop. The forty-five meters thickness of sediment encompassing the GLB in Chaotian section (Sichuan Province, South China) was sampled and processed for ostracod study. This study presents the first analysis of ostracod faunas in the GLB interval. A total of 154 species belonging to 29 genera are identified. Three species are described as new: Bairdia chaotianensis Zazzali, n. sp., Microcheilinella wujiapingensis Zazzali, n. sp., Microcheilinella pagodaensis Zazzali, n. sp. All the ostracods discovered in the section belong to shallow marine taxa. So these results are not consistent with previous interpretations (lagoonal environment or deep water setting) based on other evidences. Abundance and diversity present a rapid and noticeable decline in the Early Capitanian. Recovery is then recorded about three meters above the GLB. At specific level, a 93% extinction rate and a 96% turnover rate are recorded at the GLB. Moreover, Palaeocopida, straight dorsal border ostracods known to progressively disappear from the Late Permian to the basal Middle-Triassic, are here less abundant and diversified after the GLB. This could reflect the first step of their disappearance at the end of the Palaeozoic.

The Aguille Formation (Coniacian-Santonian) of North of Gabonese coastal basin has been analysed from the ‘Cap Esterias’ section. Palaeoecologic and paleogeographic aspects of the bivalves were taken into account. Twelve bivalve species representing 9 genera have been identified from ‘Cap Esterias’ section. Among these Acanthocardia cf. denticula (Baily, 1855), Aphrodina dutrugei (Coquand, 1862) and Protocardia cf. pauli (Coquand, 1862) are found for the first time in the ‘Cap Esterias’ region. A large part (66.67%) of the identified bivalve species occur over a wide geographical area: from Brazil to Central Africa, eastern Mediterranean region, Madagascar, Nigeria, northwestern Africa, South Africa, southern India and southern Europe. The fauna is composed only of suspension-feeders indicating that food resources were dominantly in suspension. The assemblage of bivalves is dominated by shallow burrowing infaunal bivalves and indicates the existence of an unstable and soft substrate. This assemblage can be regarded as parautochthonous.

In response to increased limb bone loads many tetrapod clades have converged upon similar adaptations to reinforce the elbow joint by reducing independent movements of the forearm bones. However prior studies have not examined how these changes occurred phylogenetically or functionally, such as during the transition from prehensile forelimbs in dinosaurs to gliding/flapping flight in bird wings. Here, a functional analysis of forearm bone mobility in extant archosaurs shows that crossing and uncrossing of the radius and ulna can be forced in alligators via a passive gliding mechanism recently described in lacertilians, while birds are adapted to inhibit this motion. A comparison of these findings with a sample of extinct quadrupedal archosaur forearms strongly suggests that, due to the highly conserved morphology of tetrapod forearms in general, the lacertilian mechanism broadly describes the plesiomorphic mechanism via which tetrapod forearm bones passively cross in response to locomotor-induced torsion. Bipedal dinosaurs retained adaptations for this passive mechanism, which indicates that they were unable to perform active long-axis rotations to align their semi-pronated, misaligned forearm joints. By contrast, analogous to birds and pterosaurs, quadrupedal dinosaurs evolved immobilizing adaptations to reduce or prohibit independent movements of the radius and ulna. Notably, the elbow joints of Archaeopteryx von Meyer, 1861 and dromaeosaurs are bird-like. This information, coupled with a lack of non-aerial adaptations for increased limb bone loads, strongly suggests that the forearms of deinonychosaurs were adapted to resist the bending and torsional stresses incurred by leading edge air streams during gliding and/or flapping.

Lithification is stressed as a major bias for the palaeobiodiversity evaluation. Although this bias is often discussed in the literature, it has rarely been quantified. This work offers a first estimation of diagenesis impact over mollusc diversity record for a single bed of the “Falunière” of Grignon (middle Lutetian, France). This bed possesses the particularity of displaying two lithological facies: one lithified and the other unlithified, both from a same taphocoenosis. Mollusc diversities of three unlithified and three lithified samples have been compared (1453 specimens among 131 species). The comparison was made possible by the construction of rarefaction curves extrapolated for 30 samples and the introduction of two indexes: the eDG (extrapolated Diagenesis Gap) that gives a value of diversity loss between two facies and the STD (sampling/diagenesis bias threshold) that gives the threshold (in number of samples) after which eDG can be estimated. The analysis reveals that nearly 80% of species richness is not recorded in the lithified facies, and that loss can reach 100% for species smaller than 2 mm. The bias linked to specimen sizes is discussed, both for large and small shells. The differences of biodiversity recorded among litholofacies have also been approached at regional level by the comparison of taxon associations from lithified and unlithified lithologies from the middle Eocene of Paris Basin (Lutetian: Vanves, Nanterre, Damery, Ferme de l'Orme, Chaussy, Grignon and Villiers-Saint-Frédéric; Bartonian: Baron), Aquitaine Basin (Bartonian: Blaye and Gironde) and Italy (Lutetian: San Giovanni Ilarione, Verona). A revaluation of biodiversity estimates of San Giovanni Ilarione that consider lithification bias suggests that the Tethyan regions housed similar or higher species richness than the Paris Basin during the Lutetian, which does not agree with a raw data comparison but which would better fit with the hypothesis of a biodiversity hotspot in the western Tethys. Any future comparisons of the biodiversity from distinct regions or time intervals have to consider the conditions of preservation and the lithification bias.

Au Burdigalien supérieur, des récifs coralliens se sont développés dans la Formation de Cala di Labra, aux alentours de Bonifacio (Corse-du-Sud, France). Ils sont organisés en trois épisodes successifs R1, R2 et R3. La faune corallienne comprenant 16 espèces récifales, est décrite pour la première fois. Deux associations coralliennes sont distinguées. Les principaux genres constructeurs sont Porites Link, 1807, Tarbellastraea Alloiteau, 1950 et Thegioastraea Sismonda, 1871. La diversité corallienne est maximale avec 15 espèces (8 genres) dans l'épisode R1, puis réduite (4 espèces appartenant à 3 genres) pour l'épisode R2, l'épisode R3 renfermant des coraux mal préservés pour être identifiés. Les formes de croissance sont en grande majorité massives étalées et superposées, associées à des conditions paléoenvironnementales de haute à moyenne énergie (rides de courant, bioclastes usés, peu de formes branchues), sous apports terrigènes réguliers. Les récifs, pour la plupart frangeants et à zonation récifale discrète, se sont développés en domaine de plate-forme peu profonde. Cette étude reprend également toutes les citations d'espèces dans la littérature pour cette région et replace ces épisodes coralliens remarquables dans l'évolution plus générale du Bassin Liguro-Provençal.