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When the "primitive" shark Tribodus (Hybodontiformes) meets the "modern" ray Pseudohypolophus (Rajiformes) : the unique co-occurrence of these two durophagous Cretaceous selachians in Charentes (SWFrance)

Vullo R., Neraudeau D.

Acta Geologica Polonica

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2008

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Vol. 58, no. 2

249-255

EN

The palaeoecology and palaeobiogeography of two Cretaceous selachian genera, Tribodus BRITO & FERREIRA, 1989 and Pseudohypolophus CAPPETTA & CASE, 1975, are briefly discussed. These two similar-sized taxa developed an analogous pavement-like grinding dentition, characterized by massive teeth with a rhomboidal to hexagonal occlusal surface. Although both genera appear to have been euryhaline forms, the hybodont Tribodus occurred in fresh/brackish water habitats (e.g. deltas) to shallow marine lagoons, whereas the ray Pseudohypolophus lived in brackish water to coastal marine environments. Palaeobiogeographically, their global distribution displays two distinct but adjoined areas, with Tribodus being present in the northern part of Gondwana (Brazil and North Africa), and Pseudohypolophus occurring on both sides of the North Atlantic (North America and Western Europe). However, the two genera coexisted during Cenomanian times within a small overlap zone, localized in western France. A trophic competition may have arisen from this situation between these two selachians belonging to the same trophic guild. This peculiar situation is well documented within the Cenomanian transgressive series of Charentes (SW France), where a turnover between the two forms is observed (replacement of Tribodus by Pseudohypolophus).

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Contribution of Eocene sharks and rays from southern France to the history of deep-sea selachians

Adnet S., Cappetta H., Reynders J.

Acta Geologica Polonica

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2008

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Vol. 58, no. 2

257-260

EN

Fossil deep-sea selachians are rare and their diversity underestimated as a consequence of the scarcity of available outcrops of sediments containing them. Here we report a new fossil locality from the Middle Eocene of southwestern France and give a first synthesis of the deep-sea deposits of this area which have yielded one of the richest fossil selachian faunas ever to have inhabited the continental slope. The fossil records of deep-sea sharks and rays are discussed in the context of these new fossil occurrences, a literature review and the recent phylogenetic hypothesis.

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Inoceramids from the Upper Campanian and Lower Maastrichtian of the Tercis section (SW France), the Global Stratotype Section and Point for the Campanian - Maastrichtian boundary; taxonomy, biostratigraphy and correlation potential

Walaszczyk I., Odin G., Dhondt A.

Acta Geologica Polonica

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2002

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Vol. 52, nr 3

269-305

EN

Thirty-three inoceramid species from the upper Upper Campanian and Lower Maastrichtian of the Tercis section (SW France), the Global Boundary Stratotype Section and Point for the Campanian - Maastrichtian boundary, are described, of which 8 are left in open nomenclature. Two species are described as new: Endocostea jolkicevi and "Inoceramus" cobbani. The described species represent four inoceramid genera Cataceramus HEINZ, 1932, Sphaeroceramus, HEINZ, 1932, Endocostea WHITFIELD, 1877, Trochoceramus HEINZ, 1932, and thirteen species are referred to the genus "Inoceramus" sensu lato. The inoceramids allow the subdivision of the upper Upper Campanian and of the Lower Maastrichtian into seven zones and their correlation with the ammonite scheme, as well as with the chronostratigraphic standard. The Campanian - Maastrichtian boundary falls in the tompost part of the "Inoceramus" redbirdensis Zone, and the base of successive, Endocostea typica Zone is a good proxy for this stage boundary. Besides the Trochoceramus costaecus Zone all other zones are also distinguishable in the US Western Interior.