Otolithes de poissons aptiens du Maestrazgo (province de Castellon, Espagne orientale)

A sampling of otoliths in the Lower Aptian sediments of the Maestrazgo provided otoliths of 18 teleost taxa of which 11 could be described as new species: Elops bultyncki, «genus Elopidarum» casanovae. «genus Albulidarum» atavus, Pterothrissus todolellanus, «genus Euteleosteorum» geometricus, «genus Protacanthopterygiorum» scalpellum, «genus Argentinidarum» bergantinus, «genus Aulopiformorum» pseudocentrolophus, «genus Synodontoideorum» pseudosphyraena, «genus Chlorophthalmidarum» manei, «genus Neoscopelidarum» maestrazgonis and «genus? Acanthomorphorum» forcallensis. This is the oldest fauna for which comparative studies of Recent and fossil otoliths still provide results which are worthy of interest. The more one goes back in time, the more morphological resemblance with Recent otoliths becomes obscure. For Aptian material, only identifications at family level or at an even higher taxonomic level are possible, except for some rare cases such as the genera Elops and Pterothrissus, which can be considered as «living fossils». For this reason, the interest of palaeoecological interpretations based on comparisons with the habitat of Recent fishes becomes very restricted if applied to Aptian faunas. The possible palaeoecological interest of analogous morphologies which are probably conditioned by function are mentioned. Finally an overview table is presented, summarising the fossil record of all Lower Cretaceous teleost families, based on data obtained from both otoliths and osteological material

Sur les otolithes des sables de Grimmertingen (Oligocène inférieur de Belgique)

Twenty-one species of teleost otoliths from the Sables de Grimmertingen are described. Six of them are new : Raniceps altus, « genus aff. Brosmopbycis » brevis, Otophidium caudatum, « genus Ophidiidarum » ornatissimus, Monomitopus grimmertingensis, « genus aff. Neobythites » spina. Although three species common to the Belgian Eocene are still present, the appearance of four typically Oligocène species together with numerous new species unknown in the Eocene suggest that these sands are of lower Oligocene age. They suggest a neritic fauna which lived in calm, somewhat deep water on a soft, muddy bottom. The abundance of gadids suggests a colder climate than that of the Eocene epoch

Influence of ligand shape and steric hindrance on the composition of the nanocrystal ligand shell

Organic ligands play a key role in the synthesis of colloidal semiconductor nanocrystals or quantum dots. Generally they consist of a functional group and an aliphatic chain, with carboxylic acids, thiols and phosphonic acids as typical examples. The functional group ensures the binding to the nanocrystal surface, while the stability of the dispersion strongly depends on the interactions between the organic chains of the adjacent ligands. A number of studies already addressed the binding strength and the type of binding between the nanocrystal surface and the ligand yet none discuss the effect of the organic chain on the ligand exchange. By means of NMR spectroscopy, we examine the ligand shell composition of CdSe nanocrystals originally capped with oleic acid (OA), when exposed to a linear carboxylic acid. Regardless of chain length, we see a one-to-one exchange between the carboxylic acids. The composition of the ligand shell closely matches that of the ligand mixture in solution, indicating that the ligand shell can be seen as an ideal mixture of both ligands. As a consequence, a mixed ligand shell can easily be prepared by adding a ligand mixture with desired composition to the nanocrystal dispersion. On the other hand, when the CdSe nanocrystals are exposed to a branched carboxylic acid with two long aliphatic chains, like 2-hexyldecanoic acid, the ligand shell mainly consists of OA moieties. We interpret these results using an exchange process where the incoming ligand not only displaces oleic acid but also occupies additional space in the ligand shell to accommodate both aliphatic chains. Hence, given a one-for-one exchange reaction, steric hindrance in a fully packed ligand shell will prevent complete ligand exchange. These results can be very useful in view of producing nanocrystals with lower ligand densities by means of synthesis with these branched carboxylic acids

Une remarquable association d’otolithes de poissons dans le Miocène moyen de Sos, Matilon (France, Lot-et-Garonne).A remarkable assemblage of fish otoliths from the Middle Miocene of Sos, Matilon (France, Lot-et-Garonne)

The Serravallian site of Sos (Matilon, base of the section) is located near to the shore of the gulf of eastern Aquitaine. The studied sediment is a near shore coquina facies with a well-preserved and diversified marine fauna, reflecting a bay environment, with some brackish influences. Otoliths of 22 teleost taxa were identified, two of them representing new species: Afroscion rezeaui and “genus aff. Afroscion” carinatus. The association is characterised by a strong dominance of sciaenids (83% of the total number of otoliths). Among the remaining taxa, Pomadasys aff. incisus and a Gobius (elongate form) account for respectively 3% and 12%; all remaining taxa are rare. Except for the Serravallian coquinas of Orthez and Sallespisse, sciaenid otoliths are very rare in all Oligo-Miocene sampling sites of Aquitaine. Sciaenids from Sos, where Afroscion rezeaui and Sciaena irregularis dominate, are different from those of Orthez and Sallespisse, dominated by Umbrina pyrenaica. Only Argyrosomus regius is common to both associations. In total, only seven species are common to the two localities, and the sparid Dentex aff. maroccanus is lacking at Sos. The two faunas seem to correspond to quite different environments. Sciaenids are quite tolerant for fresh water, and the Sos area could be near to a stream mouth at the end of the gulf. Some sciaenids are even partly freshwater fishes. At Orthez – Sallespisse, the represented sciaenids are very near shore forms, but of normal salinity: this is attested by the frequence of Dentex aff. maroccanus and several haemulids. At Mios, another rich otolith site located more to the north, otoliths essentially belong to typical marine near shore fishes, among which there are even some gadids, a family of more northern fishes; sciaenids are very rare there. Here also, environmental differences are apparently responsible for the differences among the associations

Marine Middle Eocene Otoliths from India and Java

Otoliths collected from the Harudi Formation (Lutetian) of Kachchh, Western India and from the Nanggulan Formation (Early Bartonian) of Nanggulan, Java, revealed the presence of respectively 15 and 24 teleost taxa. Seven new species are introduced: "genus Brotulinarum" siremboides, Apogon townsendoides, "genus Apogonidarum" altissimus, Lactarius nonfungus, "genus Menidarum" occultus, "genus Percoideorum" pseudatherina and "genus Percoideorum" sciaenoides. Both associations reveal very shallow neritic environments. They are compared with a previously described neritic Middle Eocene otolith association from central Western Pakistan, and a combined list of all (43) taxa represented in the three associations is provided. Considering the restricted sampling, the number (8) of taxa occuring at more than one locality is remarkable, and one can probably conclude that we sampled several of the most common and widespread teleosts inhabiting the neritic environments of the Indo-West-Pacific region during the Middle Eocene. Biogeographic evaluation of the available data leads to the conclusion that in the Eocene, the Indo-West-Pacific region was already inhabited by many fish taxa not represented elsewhere, and that probably it contained the most diverse fish community of the world, as it does today