Henri Cappetta

Deccan flood basalts at the Cretaceous/Tertiary boundary?

Abstract Joint consideration of new paleomagnetic, paleontological and geochronological data from the Deccan continental flood basalts in India and critical discussion of earlier results lead us to suggest that volcanic activity may have lasted less than 1 Ma, thus possibly ranking as one of the largest volcanic catastrophes in the last 200 Ma. Available data are best satisfied if volcanism spanned the Cretaceous/Tertiary boundary, followed shortly afterwards by rifting of the Arabian Sea. These results point out the need for further work which may help in choosing between “external” and “internal” models of the Cretaceous/Tertiary boundary events.

The assessment of REE patterns and 143Nd/144Nd ratios in fish remains

Abstract The REE content and isotopic composition of Sr and Nd have been determined in fish teeth ranging in age from the Trias to the present and from various localities mostly around the Atlantic. These measurements have been carried out on Selachian and Teleost remains from the same locality in Togo and show no appreciable difference, which suggests, with the help of a mass balance calculation of the Ce anomaly, that diagenetic effects are not responsible for the REE enrichment of biogenic phosphates. One group of fossil teeth has about 3 times the REE abundances of shale and a shale-normalized pattern with a minimum at Sm: it is thought to reflect deposition in the open-sea environment. A second group has REE concentration about 10 times higher than the first group with either a regular light REE enrichment or, more frequently, a maximum in the middle REE, both being probably indicative of deposition in estuarine or near-shore conditions. The shape of the REE spectra and the size of the Ce anomaly can be used semi-quantitatively to determine the depth of deposition. The results presented here on Late Cretaceous/Eocene fish teeth samples from Morocco reflect an increasing influx of deep waters with a lowLa/Yb ratio and strong negative Ce anomaly, which agrees well with the evolution of sediment chemistry and microfauna associations. In contrast, ɛNd is typical of the water mass in which the fish debris decayed. Examples of nearly isolated basins identified with Nd isotopes include the South Atlantic prior to the Lutetian (ɛNd ≈ −13.5), the Miocene Persian Gulf (ɛNd = −3.1), and Bolivia during the Late Cretaceous (ɛNd = −12.8). Togo and Guinea-Bissau results suggest that, in the South Atlantic, the meridional oceanic circulation had not started before 45 Ma ago. Combination of REE andɛNd data suggests that the assignment of Jurassic-Cretaceous samples measured so far to open-sea water masses is still ambiguous.

Fish tooth δ18O revising Late Cretaceous meridional upper ocean water temperature gradients

The oxygen isotope composition of fossil fi sh teeth, a paleo– upper ocean temperature proxy exceptionally resistant to diagenetic alteration, provides new insight on the evolution of the low- to middlelatitude thermal gradient between the middle Cretaceous climatic optimum and the cooler latest Cretaceous period. The new middle Cretaceous low to middle latitude thermal gradient agrees with that previously inferred from planktonic foraminifera δ 18O recovered from Deep Sea Drilling Project and Ocean Drilling Program drilling sites, although the isotopic temperatures derived from δ 18O of fish teeth are uniformly higher by ~3–4 °C. In contrast, our new latest Cretaceous thermal gradient is markedly steeper than those previously published for this period. Fish tooth δ18O data demonstrate that low- to middle-latitude thermal gradients of the middle Cretaceous climatic optimum and of the cooler latest Cretaceous are similar to the modern one, despite a cooling of 7 °C between the two periods. Our new results imply that no drastic changes in meridional heat transport are required to explain the Late Cretaceous climate. Based on climate models, such a cooling without any change in the low to middle latitude thermal gradient supports an atmospheric CO2 decrease as the primary driver of the climatic evolution recorded during the Late Cretaceous.

The marine vertebrate faunas from the Late Cretaceous phosphates of Syria

Marine vertebrate faunas from the latest Cretaceous phosphates of the Palmyrides Chain of Syria are described for the first time. Recent fieldwork in the phosphatic deposits of the Palmyra area (mines of Charquieh and Khneifiss, outcrops of Bardeh, Soukkari and Soukhneh) have yielded a rich and diversified assemblage of marine vertebrates, including more than 50 species of chondrichthyes, osteichthyes, squamates, chelonians, plesiosaurians and crocodilians. Selachians are the most abundant and diverse component of the faunas and are represented by at least 34 species of both sharks and rays. Actinopterygians include representatives of six families, the most common being the enchodontids. Squamates are known by six mosasaurid species and an indeterminate varanoid. Chelonians are represented by at least two bothremydids and two chelonioids. Finally, elasmosaurid plesiosaurs and indeterminate crocodilians are also present in the fossil assemblages. The difference in faunal composition observed between the sites is interpreted as being due to palaeoecological preferences related to the Hamad Uplift palaeostructure. The marine vertebrate faunas of Syria show close affinities with those of the latest Cretaceous phosphatic deposits of North Africa and the Middle East and are typical of the southern Tethyan realm. From a biostratigraphical point of view, the selachians are the only suitable material to provide elements of an answer to the long debated question of the age of the Syrian Senonian phosphates. They suggest an Early Maastrichtian age for most of the phosphates of the Palmyrides Chain.

δ18O values of coexisting brachiopods and fish: Temperature differences and estimates of paleo–water depths

To estimate vertical thermal gradients and paleo–water depths to marine platforms we present a new method based on the difference between δ 18 O values of contemporaneous brachiopod carbonate and fish phosphate. Present-day marine fauna of well-known ecology from the surface to the sea floor record isotopic temperatures that agree with measured temperatures. We predict distributions of isotopic data that result from sampling strategy, basin morphology, and fauna ecology and discuss limitations. Application of the method to the Jurassic Paris-London basin gives vertical thermal variations of up to 14 °C associated with depths varying from a few meters to 170 ± 30 m. The estimated depths are minimum values and are greater than those estimated from sedimentological criteria for this ancient epicontinental sea.

A Middle-Late Eocene vertebrate fauna (marine fish and mammals) from southwestern Morocco; preliminary report: age and palaeobiogeographical implications

Recent field work in the southern Moroccan Sahara (‘Western Sahara’), south of the city of ad-Dakhla, has led to the discovery of several new fossiliferous sites with fossil vertebrates in sedimentary deposits previously reported for the Mio-Pliocene. The sedimentology and geological setting of the studied area are briefly reported here, and at least three units have been identified in successive stratigraphical sequences according to their fossil content. The first preliminary list of vertebrate associations is reported and consists mainly of isolated teeth belonging to selachian and bony fishes, a proboscidean tooth currently assigned to ? Numidotherium sp. and many remains of archaeocete whales (Basilosauridae). At least 48 species of selachians are presently identified; many of them are new and others are recorded in the late Middle Eocene (Bartonian) and Late Eocene (Priabonian) of Wadi Al-Hitan (Egypt) or Wadi Esh-Shallala Formation (Jordan) as in other African localities (e.g. Otodus cf. sokolowi, ‘Cretolamna’ twiggsensis, Xiphodolamia serrata, Misrichthys stromeri, Hemipristis curvatus, Galeocerdo cf. eaglesomi, Propristis schweinfurthi ), probably indicating a Late Eocene age for unit 2 of the bedrock successions. The evolutionary trend noticeable on the proboscidean tooth is in agreement with such an assumption, by comparison with the close relative species known from the Eocene of Egypt, Libya and Algeria. Indeed, the faunal associations from the Dakhla area clearly demonstrate the erroneous age of these deposits, previously thought to be Mio-Pliocene. It suggests a correlation in age (late Middle Eocene–Late Eocene) and a similar environment with the famous marine deposits from Egypt and Jordan. It opens new opportunities to understand the biogeography and the surprising similarity of landscape between West and Northeast Africa during the Bartonian–Priabonian period.

An Analytical Approach for Estimating Fossil Record and Diversification Events in Sharks, Skates and Rays

Background Modern selachians and their supposed sister group (hybodont sharks) have a long and successful evolutionary history. Yet, although selachian remains are considered relatively common in the fossil record in comparison with other marine vertebrates, little is known about the quality of their fossil record. Similarly, only a few works based on specific time intervals have attempted to identify major events that marked the evolutionary history of this group. Methodology/Principal Findings Phylogenetic hypotheses concerning modern selachians’ interrelationships are numerous but differ significantly and no consensus has been found. The aim of the present study is to take advantage of the range of recent phylogenetic hypotheses in order to assess the fit of the selachian fossil record to phylogenies, according to two different branching methods. Compilation of these data allowed the inference of an estimated range of diversity through time and evolutionary events that marked this group over the past 300 Ma are identified. Results indicate that with the exception of high taxonomic ranks (orders), the selachian fossil record is by far imperfect, particularly for generic and post-Triassic data. Timing and amplitude of the various identified events that marked the selachian evolutionary history are discussed. Conclusion/Significance Some identified diversity events were mentioned in previous works using alternative methods (Early Jurassic, mid-Cretaceous, K/T boundary and late Paleogene diversity drops), thus reinforcing the efficiency of the methodology presented here in inferring evolutionary events. Other events (Permian/Triassic, Early and Late Cretaceous diversifications; Triassic/Jurassic extinction) are newly identified. Relationships between these events and paleoenvironmental characteristics and other groups’ evolutionary history are proposed.

Sur quelques sélaciens nouveauxdu Crétacé supérieur de Bolivie: Amérique du Sud

The locality of Torotoro (Puca Group, Upper Cretaceous of Bolivia) has yielded a small shark-fauna including a new genus and five new species: Pucabatis hoffstetteri nov. gen., nov. sp., Ischyrhiza hartenbergeri nov. sp., Dasyatis branisai nov. sp., D. molinoensis nov. sp. et D. schaefferi nov. sp. The genus Pucapristis, previously described on rostral teeth, is represented by numerous oral teeth unknown until this day. The occurence of the genus Schizorhiza, already pointed out, allows to attribute the El Molino formation to maestrichtian.

Sharks (Elasmobranchii: Euselachii) from the Late Cretaceous of France and the UK

Bulk-sampling of 22 phosphatic horizons from the Upper Cretaceous of northern France and the UK has yielded very rich selachian faunas dominated by shark taxa. These samples, collected from Cenomanian to Campanian Chalks and one glauconitic sediment, allow the identification of numerous new taxa, and improve our knowledge of northern European Late Cretaceous selachian assemblages, with a special focus on small to minute remains that were previously overlooked. Among the 96 taxa described here, 18 species and four genera are newly described: Protosqualus barringtonensis sp. nov., Heterodontus boussioni sp. nov., Heterodontus laevis sp. nov., Adnetoscyllium angloparisensis gen. et sp. nov., Chiloscyllium frequens sp. nov., Chiloscyllium vulloi sp. nov., Pararhincodon ornatus sp. nov., Cederstroemia siverssoni sp. nov., Pseudocorax duchaussoisi sp. nov., Squalicorax bernardezi sp. nov., Eoptolamna supracretacea sp. nov., Anomotodon genaulti sp. nov., Scyliorhinus monsaugustus sp. nov., Scyliorhinus muelleri sp. nov., Sigmoscyllium acuspidatum gen. et sp. nov., Palaeotriakis gen. nov., Paratriakis robustus sp. nov., Platyrhizodon gracilis gen. et sp. nov. and Platyrhizodon barbei gen. et sp. nov. In addition, numerous potential new taxa are left in open nomenclature pending the discovery of more material. Stratigraphical and geographical ranges of taxa are updated and observations on the dentition of a few species (Anomotodon hermani, Cederstroemia, Carcharias latus, Palaeotriakis, Paratriakis) are made. An updated Late Cretaceous selachian fossil record and global standing diversity are also presented. http://zoobank.org/urn:lsid:zoobank.org:pub:BBDF3FE8-CF78-4601-AA10-74216BE32768

Enameloid microstructure of some Cretaceous Hexanchiformes and Synechodontiformes (Chondrichthyes, Neoselachii): New structures and systematic implications

Modern neoselachian sharks may be separated from more basal relatives by the presence of tooth enameloid comprising three layers. Although enameloid microstructure studies were mostly used in the aim of differentiating supposed basal neoselachians from hybodonts, differences in the enameloid organization among neoselachians have been recognized suggesting the potential for use of enameloid microstructure as a phylogenetic tool within the neoselachian sharks. The enameloid microstructure of five taxa of neoselachian sharks belonging to two orders, the Hexanchiformes and Synechodontiformes, has been studied. The Hexanchiformes are a monophyletic order with extant representatives, whereas the extinct Synechodontiformes have been considered as monophyletic, paraphyletic, or polyphyletic by different authors. This study has revealed numerous new enameloid microstructures such as amalgamated crystallites in the internal units [parallel‐bundled enameloid (PBE) and tangled‐bundled enameloid], cavities at the shiny‐layered enameloid (SLE)/PBE boundary, radial furrows in the PBE, as well as different original organizations at the base of the crown and in the PBE at the level of the cutting edges. Pachyhexanchus pockrandti (Hexanchiforme) and Welcommia bodeuri have the most of the features in common and they share more characters with those of Paraorthacodus sp. and Sphenodus sp. than with Synechodus sp. Microsc. Res. Tech., 2010.