David J. Ward

Cretaceous Extinctions: Multiple Causes

![Figure][1] Deccan plateau basalts. Lava from Deccan volcanism formed distinct layering. CREDIT: GSFC/NASA In the Review “The Chicxulub Asteroid Impact and Mass Extinction at the Cretaceous-Paleogene boundary” (P. Schulte et al. , 5 March, p. [1214][2]), the terminal Cretaceous

Surface-water freshening and high-latitude river discharge in the Eocene North Sea

Abstract: A shark-tooth apatite δ18O record of the early Palaeogene North Sea reflects changes in regional hydrography by showing variable temperatures and salinities. A 2–4 Ma period in the early Eocene was particularly influenced by substantial surface-water freshening, indicated by a 3–4‰ reduction of δ18O values. The magnitude of the δ18O decrease indicates a depletion in 18O of surface waters by 2–3‰ relative to Eocene mean ocean water. This value is lower than that of coeval lakes reconstructed from freshwater gastropod δ18O values from the Paris Basin, suggesting that large rivers with high-latitude catchment areas drained into the North Sea. The period of surface-water freshening began close to the Palaeocene – Eocene thermal maximum, when relative sea-level fall, tectonic uplift and basaltic volcanism caused a temporary isolation of the North Sea. North Atlantic and North Sea surface waters became reconnected during a series of early Eocene transgressions.

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

The first record of lizards and amphibians from the Wessex Formation (Lower Cretaceous: Barremian) of the Isle of Wight, England

The Lower Cretaceous beds of the Wessex Formation of the Isle of Wight are renowned worldwide for their dinosaur fauna, but traces of associated small tetrapods have been harder to find. Here we report the first definitive records, albeit fragmentary, of lizards and terrestrial amphibians (frogs, albanerpetontids) recovered by screen-washing sediments from the type locality of the theropod dinosaur Neovenator.

A climatic control on reorganization of ocean circulation during the mid-Cenomanian event and Cenomanian-Turonian oceanic anoxic event (OAE 2): Nd isotope evidence

Although ocean circulation plays a vital role in the climate system, its response to major carbon-cycle perturbations during the mid-Cretaceous, including mid-Cenomanian event I (MCE I) and the Cenomanian-Turonian oceanic anoxic event (OAE 2), is poorly constrained. Here we present Nd isotope evidence for episodic increases in the influence of boreal seawater in the European epicontinental sea during MCE I. The start of this circulation reorganization lagged the onset of the δ13C positive excursion defining MCE I. This sequence of change is similar to that observed during OAE 2 in the same area, showing a consistent response of regional circulation to changes in the global carbon cycle. Brief intervals of invasion of boreal fauna to mid-latitude seas, two during MCE I and one during OAE 2 (Plenus cold event), all started after the influence of boreal seawater was enhanced, implying a slower biological response to climate cooling rather than passive transport of fauna by boreal waters. The lack of an Nd isotope positive excursion in our record across MCE I supports a volcanic origin for prominent increases in seawater Nd isotope values found in the European epicontinental sea and the tropical Atlantic during OAE 2. The observed tight circulation–carbon cycle coupling may help the upper ocean replenish nutrients from deep waters and/or volcanic sources, providing a critical feedback allowing continuation of MCE I and OAE 2 over long durations.

†Tingitanius tenuimandibulus, a new platyrhinid batoid from the Turonian (Cretaceous) of Morocco and the cretaceous radiation of the Platyrhinidae

ABSTRACT An exceptionally well-preserved specimen of a batoid from the Turonian (Late Cretaceous) of Morocco has been named as †Tingitanius tenuimandibulus, sp. nov. The fossil has been identified as a member of the Platyrhinidae and represents the oldest known example of a thornback ray. Mechanical and acid preparation of the ventral surface has revealed the general body form of the specimen and permitted teeth and three morphotypes of dermal denticles to be extracted. Computed tomographic (CT) scanning of the chondrocranium and thoracic region has allowed the detailed study of the skeletal elements concealed within the rock. The phylogenetic position of the new specimen and implications for the phylogenetic positions of the ‘rhinobatoids’ are discussed. †Britobatos, gen. nov., is erected to accommodate †Raja primarmata which is here shown to be a sister taxon to the Platyrhinidae including †Tingitanius. It is likely that reassessment of isolated batoid teeth from the Cretaceous and Paleogene will confirm the former importance of the Platyrhinidae.

Neoselachians from the Danian (Early Paleocene) of Denmark

A diverse elasmobranch fauna was collected from the early Danian Rødvig Formation and the early to middle Danian Stevns Klint Formation at Stevns Klint and from the middle Danian Faxe Formation at Faxe, Denmark. Teeth from 27 species of sharks are described including the earliest records of Chlamydoselachus and Heptranchias howelli from Europe. The fauna collected at the Faxe quarry is rich in large species of shark including Sphenodus lundgreni and Cretalamna appendiculata and includes no fewer than four species of Hexanchiformes. The species collected yield an interesting insight into shark diversity in the Boreal Sea during the earliest Paleogene. The early Danian fauna recorded from the Cerithium Limestone represents an impoverished Maastrichtian fauna, whereas the fauna found in the slightly younger bryozoan limestone is representative of a pronounced cold water fauna. Several species that hitherto have only been known from the Late Cretaceous have been identified, clearly indicating that the K–T boundary was not the end of the Cretaceous fauna; it lingered and survived into the early Danian.

Batoids (Elasmobranchii: Batomorphii) from the British and French Late Cretaceous

Bulk sampling of phosphatic horizons from the Late Cretaceous of the Anglo-Paris Basin and Northern Ireland yielded very rich and high diversity selachian faunas. Amongst them, batoid remains (rays and skates) are commonly present and diverse although never a dominant element of these assemblages. The following new taxa are described: Cretaplatyrhinoidis ornatus gen. et sp. nov., Pseudoplatyrhina crispa gen. et sp. nov., ‘Rhinobatos’ seruensis sp. nov., Squatirhina draytoni sp. nov., Agaleorhynchus britannicus gen. et sp. nov. and Ptychotrygonoides sabatieri sp. nov. Batoids are described for the first time from post-Cenomanian Late Cretaceous deposits of England and the dentition of species of the genus Squatirhina is described and discussed. The Platyrhinidae described here represent the oldest known records for the family and the Cenomanian material identified as Dasyatoidea indet. is one of the rare remains of the order Myliobatifomes from pre-Campanian horizons. Evolutionary and palaeoecological observations are also discussed.

A new elusive otodontid shark (Lamniformes: Otodontidae) from the lower Miocene, and comments on the taxonomy of otodontid genera, including the ‘megatoothed’ clade

Abstract We describe a new large otodontid lamniform shark, Megalolamna paradoxodon gen. nov. et sp. nov., chronostratigraphically restricted to the early Miocene (Aquitanian–Burdigalian). This new species is based on isolated teeth found from five globally distributed localities: the Jewett Sand in southern California, USA; the Pungo River Formation of North Carolina, USA; the Chilcatay Formation of Peru; the Oi Formation in Mie Prefecture, Japan; and the O’oshimojo Formation in Nagano Prefecture, Japan. Extrapolations based on available published data on modern macrophagous lamniforms suggest that the largest specimen of M. paradoxodon gen. nov. et sp. nov. possibly came from an individual that measured at least 3.7 m in total length. All specimens came from deposits in the mid-latitudinal zones representing shallow-water, shelf-type, coastal environments. Its dentition likely exhibited monognathic heterodonty suited for capturing and cutting relatively large prey (e.g. medium-sized fishes). We recommend the genus Otodus to include sharks of the ‘megatoothed’ (e.g. megalodon) lineage in order to avoid Otodus paraphyly. We also propose the following phylogenetic hypothesis: [Kenolamna + [Cretalamna + [Megalolamna + Otodus]]]. ZooBank LSID for the genus Megalolamna is: urn: lsid:zoobank.org:act:B4791DEF-4D96-4FEB-9B7B-0EF816B96079 ZooBank LSID for the species Megalolamna paradoxodon is: urn:lsid:zoobank.org:act:7D3D7442-53C6-43A2-9E8D-6339729565B6

Miocene Shark and Batoid Fauna from Nosy Makamby (Mahajanga Basin, Northwestern Madagascar)

Madagascar is well known for producing exceptional fossils. However, the record for selachians remains relatively poorly known. Paleontological reconnaissance on the island of Nosy Makamby, off northwest Madagascar, has produced a previously undescribed assemblage of Miocene fossils. Based on isolated teeth, ten taxonomic groups are identified: Otodus, Carcharhinus, Galeocerdo, Rhizoprionodon, Sphyrna, Hemipristis, Squatina, Rostroraja, Himantura and Myliobatidae. Six are newly described from Madagascar for the Cenozoic (Galeocerdo, Rhizoprionodon, Sphyrna, Squatina, Rostroraja and Himantura). In association with these specimens, remains of both invertebrates (e.g., corals, gastropods, bivalves) and vertebrates (e.g., bony fish, turtles, crocodylians, and sirenian mammals) were also recovered. The sedimentary facies are highly suggestive of a near-shore/coastal plain depositional environment. This faunal association shares similarities to contemporaneous sites reported from North America and Europe and gives a glimpse into the paleoenvironment of Madagascar’s Miocene, suggesting that this region was warm, tropical shallow-water marine.