Worldwide Genotyping in the Planktonic Foraminifer Globoconella inflata: Implications for Life History and Paleoceanography

The planktonic foraminiferal morpho-species Globoconella inflata is widely used as a stratigraphic and paleoceanographic index. While G. inflata was until now regarded as a single species, we show that it rather constitutes a complex of two pseudo-cryptic species. Our study is based on SSU and ITS rDNA sequence analyses and genotyping of 497 individuals collected at 49 oceanic stations covering the worldwide range of the morpho-species. Phylogenetic analyses unveil the presence of two divergent genotypes. Type I inhabits transitional and subtropical waters of both hemispheres, while Type II is restricted to the Antarctic subpolar waters. The two genetic species exhibit a strictly allopatric distribution on each side of the Antarctic Subpolar Front. On the other hand, sediment data show that G. inflata was restricted to transitional and subtropical environments since the early Pliocene, and expanded its geographic range to southern subpolar waters ∼700 kyrs ago, during marine isotopic stage 17. This datum may correspond to a peripatric speciation event that led to the partition of an ancestral genotype into two distinct evolutionary units. Biometric measurements performed on individual G. inflata from plankton tows north and south of the Antarctic Subpolar Front indicate that Types I and II display slight but significant differences in shell morphology. These morphological differences may allow recognition of the G. inflata pseudo-cryptic species back into the fossil record, which in turn may contribute to monitor past movements of the Antarctic Subpolar Front during the middle and late Pleistocene

The Messinian Salinity Crisis in the Dacic Basin (SW Romania) and early Zanclean Mediterranean-Eastern Paratethys high sea-level connection

International audienceNew field observations and fossil analyses complete and clarify the strong impact of the Mediterranean sea-level changes linked to the peak of the Messinian Salinity Crisis on the Dacic Basin in southwestern Romania. In addition to the Gilbert-type fan delta already evidenced along the Danube River in the area of Turnu Severin, a new Gilbert-type fan delta is described northward. Early Zanclean bottomset beds are evidenced and dated based on nannofossils at the junction of the two coalescing Gilbert-type fan deltas. A clear sedimentological, morphological and chronologic differentiation is established in the area between the Carpathians Late Miocene piedmont alluvial fans and the early Zanclean Gilbert-type fan deltas. The early Zanclean age of the Hinova clays, where the bottomset beds of the Gilbert-type fan deltas are mostly developed, is confirmed by the occurrence of nannofossil markers of Subzone NN12b and a Bosphorian mollusk macrofauna. Early Zanclean inflow of Mediterranean marine waters into the Dacic Basin is also supported by the record of planktonic foraminifers. In the Dacic Basin, the Messinian Salinity Crisis resulted in the cutting of the Iron Gates by a Carpathians river. Fluvial erosion also affected the residual Pannonian Basin and probably catched the paleo-Tisza River which contributed to the erosion of the Iron Gates and to the fluvial drainage of the partly desiccated Dacic Basin. Arguments are reinforced in favor of a marine gateway between the Mediterranean and Dacic Basin through the Balkans before and after the Messinian Salinity Crisis

New insights on the Sorbas Basin (SE Spain): the onshore reference of the Messinian Salinity Crisis

International audienceThe Sorbas Basin is the land reference of the Messinian Salinity Crisis (MSC) that affected the Mediterranean Sea in the latest Miocene. Its stratigraphy has been re-visited using calcareous nannofossils and planktonic foraminifers, which provide a reliable biostratigraphic frame and lead to particularly specify the relationships between the Sorbas and Zorreras members with Yesares evaporites.The evaporites overlie a shallowing upward sequence ending with the deposition of the Reef Unit and Terminal Carbonate Complex (TCC) on the periphery of the basin. The reefal carbonates of the TCC are overlain by clastic deposits that are foreset beds of post-MSC Gilbert-type fan deltas developed on the northern edge of the basin. These sedimentary structures are separated from reefal carbonates and the Reef Unit by the Messinian Erosional Surface (MES). The various facies of the Sorbas Member have been correlated with the bottomset beds of the Gilbert-type fan deltas despite some differences in palaeobathymetry. In the southeastern periphery of the basin, the MES separates the Sorbas Member from the Yesares gypsums. In the central part of the basin, a hiatus characterizes the contact between these members. The Zorreras Member postdates the MSC and entirely belongs to Zanclean. Its white “Lago Mare” layers are lagoonal deposits, the fauna of which is confirmed to result from Mediterranean–Paratethys high sea-level exchange after the post-MSC marine reflooding of the Mediterranean Basin.This study allows to re-assert the two-step scenario of the MSC (Clauzon et al., 1996) with the following events:- at 5.971–5.600 Ma, minor sea-level fall resulting in the desiccation of this peripheral basin with secondary fluctuations;- at 5.600–5.460 Ma, significant subaerial erosion (or lack of sedimentation) caused by the almost complete desiccation of the Mediterranean Sea;- instantaneous marine reflooding, accepted at 5.460 Ma, followed by continuing sea-level rise

Osteological description of the braincase of Rhabdodon (Dinosauria, Euornithopoda) and phylogenetic implications

International audienceDeux gisements situés sur la commune de Cruzy (Hérault, France), dont les associations fauniques indiquent un âge campanien supérieur - maastrichtien inférieur, ont chacun livré un arrière-crâne que nous attribuons au genre Rhabdodon. L'occiput provenant du gisement de Massecaps (M4) est partiel mais exceptionnellement bien conservé. Cet occiput appartenait à un individu juvénile, comme l'indique la présence de lignes de sutures clairement visibles entre les différentes pièces osseuses. L'occiput du gisement de Montplô Nord (MN25) est partiel, largement déformé et appartenait à un individu adulte. Jusqu'à maintenant, les restes d'ornithopodes du Crétacé supérieur du Sud de la France ont été attribués soit aux Hadrosauridae, soit à Rhabdodon. Les ornithopodes évolués (Hadrosauridae) possèdent, d'une part, une faible crête nuchale, et d'autre part, des exoccipitaux qui se rejoignent pour former une barre plus ou moins épaisse dorso-ventralement sur le bord dorsal du foramen magnum, excluant ainsi le supraoccipital de ce bord. L'absence de crête nuchale sur le supraoccipital et la participation de ce dernier au bord dorsal du foramen magnum sur les spécimens M4 et MN25, impliquent une attribution au genre Rhabdodon. Les arrière-crânes M4 et MN25 ont été comparés à un occiput juvénile de Tenontosaurus tilletti, un Iguanodontia basal du Crétacé inférieur nord-américain, considéré comme groupe frère de Rhabdodon. Malgré de nombreux caractères partagés, notre étude révèle que l'arrière-crâne de Rhabdodon présente des caractères plus primitifs que ceux de Tenontosaurus Les exoccipitaux de Tenontosaurus se rejoignent au niveau de la surface dorsale du foramen magnum pour former une barre sur le bord dorsal du foramen magnum. D'après Norman [1984], ce renforcement accompagné d'autres adaptations sur le crâne, permettrait de réduire le stress occasionné par une mastication plus élaborée. Rhabdodon apparaît donc comme membre du clade à mastication plus primitive des " hypsilophodontoïdes ", chez qui les exoccipitaux sont exclus de la marge dorsale du foramen magnum. Chez Tenontosaurus tilletti, la bande formée par la réunion des exoccipitaux est beaucoup moins étendue dorso-ventralement que chez les " iguanodontoïdes " ou les " hadrosauroïdes ". Tenontosaurus semble donc former un groupe intermédiaire entre le clade des " hypsilophodontoïdes " et celui des " iguanodontoïde

Reassessing the age of Karpathos ophiolite (Dodecanese, Greece): consequences for Aegean correlations and Neotethys evolution

International audienceWhile the Neogene history of the Eastern Mediterranean region is now fairly well understood,our knowledge of older regional palaeogeographies is less accurate, especially the positions ofblocks and nappes constituting the Aegean Islands prior to the Cenozoic. Our study focuses onthe ophiolite exposed on the island of Karpathos (Dodecanese), which is located in the Aegeanfore-arc at a pivotal position between the ‘western’ and ‘eastern’ ophiolites of the Mediterraneanregion and where conflicting Late Jurassic and Late Cretaceous ages have led to diverging tectonicand palaeogeographic interpretations. To test these ages, we targeted the radiolariancherts that depositionally overlie the ophiolite and extracted diagnostic radiolarian assemblagesofAptian (∼125−113Ma), early–middle Albian (∼113−105Ma) and Turonian (∼93.9−89.8Ma)ages. These results suggest that previous Late Cretaceous K–Ar isotopic ages (from 95.3 ± 4.2 Mato 81.2 ± 1.6 Ma) may have been reset by Late Cretaceous metamorphism or affected by argonloss. Overall, the new Early Cretaceous ages show that the Karpathos ophiolite should not becorrelated with the Pindos Nappes of Greece or the ophiolites of Cyprus or Syria but rather withthe Lycian Nappes of Turkey and their root located in the Izmir–Ankara–Erzincan Suture Zone.Therefore, the Karpathos ophiolite represents a remnant of the Northern Neotethys, not thePindos Ocean or the proto-Eastern Mediterranean Basin

Revised Paleogene planktonic foraminiferal biozonation for the Austral Realm

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PALEOGENE PLANKTONIC FORAMINIFERAL BIOZONATION FOR THE AUSTRAL REALM

The Antarctic Paleogene planktonic foraminifer zonation was revised by Huber and Quillévéré (2005) using the most consistent and reliable planktonic foraminifer first and last occurrence events that can be correlated among southern high latitude sites. Shorthand prefixes for the Antarctic Paleogene zones have been created to include ‘AP' zones for the ‘Antarctic Paleocene', ‘AE' zones for the ‘Antarctic Eocene', and ‘AO' zones for the ‘Antarctic Oligocene'. In this chapter the zonal definitions, magnetostratigraphic calibration, and estimated ages are summarized for each of the Antarctic Eocene zones and Zone AP4

Ontogenetic and evolutionary patterns of shape differentiation during the initial diversification of Paleocene acarininids (planktonic foraminifera)

International audiencePrevious studies have established a close relationship between the evolutionary origin of new clades of planktonic foraminifera and heterochrony. Studies of the Paleogene radiation of the genus Morozovella revealed, for example, a temporal pattern of variation consistent with paedomorphosis. Our study focused on the late Paleocene species of Acarinina , sister group of Morozovella. Shape variations related to evolution and ontogeny are appraised through a morphometric method based on outline analysis using the elliptic Fourier transform. Patterns of developmental and evolutionary changes are studied and compared within each species ( Acarinina nitida, A. subsphaerica , and A. mckannai ). As no congruence is found, we suggest that the evolutionary change observed within these species is not related to a heterochronic process. We also test for similarity of both evolutionary and ontogenetic changes among species. Although we observe no significant correlation between temporal patterns of shape change among species, the tight congruence of ontogenetic trajectories suggests that the developmental constraints affecting these trajectories have been preserved in spite of the evolutionary diversification of acarininids. Heterochrony is not clearly involved in the early Paleogene diversification of acarininids and therefore may not be as common as previously claimed. The role of developmental constraints in monitoring morphological evolution therefore needs to be reassessed

Transient ocean warming and shifts in carbon reservoirs during the early Danian

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