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We present the first known cranial remains of the fossil batoid † Onchopristis numidus. Based on two exceptionally well-preserved specimens collected from the 'Kem Kem Beds' (Albian–Cenomanian), south-east Morocco, an almost complete description of the rostral and cranial portions of the genus †O nchopristis is provided, together with new observations regarding the development and arrangement of the rostral denticle series for this genus. The comparison between the rostrum length of the specimens of † O. numidus with those of extant pristids, reveals a relatively large batoid species with an estimated total length between two and four metres. Overall, the cranial morphology of † Onchopristis resembles that of other sclerorhynchoids. Its robust hypertrophied rostrum, with the characteristic wood-like mineralization covering the inner layer of tessellate cartilage at the centre of the rostrum, in addition to the thick lateral layers of densely porous cartilage on the sides of the rostral cartilages, resembles that observed in † Ischyrhiza and † Schizorhiza , and differentiates † Onchopristis from other sclerorhynchoids (e.g. † Libanopristis , † Micropristis and † Sclerorhynchus). Aiming to determinate the phylogenetic relations of † Onchopristis within sclerorhynchoids, a cladistic analysis was carried out based on the remains described here; its results suggest a new taxonomic arrangement within the sclerorhynchoids. [ABSTRACT FROM AUTHOR]

A new fossil batoid (ray) Ptychotrygon rostrispatula sp. nov. is described from five exceptionally well‐preserved, three‐dimensional skeletal remains from the Turonian (Late Cretaceous) of Morocco. These specimens represent the first known skeletal remains for the genus Ptychotrygon and allow an almost complete description of the genus, providing a new insight into its phylogenetic relations and validating its taxonomic status as a member of the Sclerorhynchoidei. Mechanical preparation of the fossil remains revealed a relatively large batoid species (estimated total length above 1 m). Overall the morphology resembles that of sclerorhynchoids, with a robust hypertrophied rostrum that lacks enlarged rostral denticles with enlarged paddle‐like pectoral proximal elements (propterygium, mesopterygium and metapterygium). Never before seen details of the branchial skeleton are presented (large second hypobranchial without anterior process, which was probably fused to the basibranchial and no evidence of articulation with other branchial element). To assess the phylogenetic relations of these specimens within the sclerorhynchoids a parsimonious analysis using TNT and PAUP was performed. These analyses included Asflapristis cristadentis and Ptychotrygon rostrispatula sp. nov., which were used as representatives of Ptychotrygonidae, and also includes six other genera of sclerorhynchoids with relatively good skeletal remains. Both analyses recovered two monophyletic groups within sclerorhynchoids: the first contains Ischyrhiza, Onchopristis and Schizorhiza, and a second that includes Micropristis, Sclerorhynchus, Libanopristis and Ptychotrygonidae. [ABSTRACT FROM AUTHOR]

A new fossil batoid (ray), Asflapristis cristadentis gen. et sp. nov., is described from six exceptionally well-preserved, three-dimensional skeletal remains from the Turonian (Late Cretaceous) of Morocco. Mechanical and acid preparation and computed tomographic scanning of these specimens reveal details of much of the proximal skeleton, especially the skull, synarcual and pectoral skeleton, with only the more distal parts of the skeleton missing. These fossils represent a relatively large animal (62 cm preserved length, estimated total length approximately 2 metres) possessing a robust rostrum that lacks enlarged rostral denticles. It has a narrow and small chondrocranium with jaws that are relatively large compared to the rest of the skull and robust with highly ornamented teeth that lack cusps. The branchial skeleton shows a large second hypobranchial without an anterior process, which was probably fused to the basibranchial as in other sclerorhynchoids. The synarcual is large and lacks centra through its entire length, with no direct connection to the pectoral girdle observed. Pectoral fins probably possessed enlarged proximal elements (propterygium, mesopterygium and metapterygium); the articulation facet between the coracoid and the pectoral elements was reduced. A phylogenetic analysis using both parsimony and Bayesian methods was performed incorporating this new taxon. Both analyses recovered a phylogenetic topology that places the sclerorhynchoids in a close relation to rajoids and clearly separated from the morphologically similar Pristidae within the Rhinopristiformes. With respect to the extant taxa, the phylogenies generated are similar to that obtained from molecular analysis of modern batoids. The palaeoecological implication of this discovery suggests that the Asfla assemblage was not from a 'normal' open carbonate shelf but rather a restricted environment favouring a low-diversity chondrichthyan fauna. [ABSTRACT FROM AUTHOR]

The chondrichthyan faunas from the Danish Maastrichtian chalk and the K/ T boundary clay, the Fiskeler, are described for the first time. The rich and diverse fauna discovered in the late Maastrichtian chalk experienced a massive drop in diversity prior to the boundary. However, the fauna started to recover immediately after the deposition of the impact layer during earliest Danian times and had regained much of its diversity during the first few millennia after the bolide impact. Precision sampling has made it possible to document the recovery of the fauna, which did not suffer an extinction event of the same magnitude, as apparently observed in Morocco. At Stevns Klint, only 33 per cent of the chondrichthyan fauna became extinct compared with the 96 per cent in Morocco. The drop in diversity before the boundary is attributed to a sudden change in sea level. Among the sharks found in the chalk and Fiskeler are rare species such as Parasquatina and Echinorhinus and the first representative of Nebrius in Europe. [ABSTRACT FROM AUTHOR]

Abstract: We describe the manual and digital methods used to prepare an exceptional fossil specimen, as well as the composition of this specimen revealed by these methods. The fossil, a rhinobatoid, is 3-dimensionally preserved in a concretion. Fossils like these are seldom encountered, because flat-bodied animals are traditionally preserved in lithographic beds, or more commonly, are only represented by disassociated dentition. Manual preparation was best conducted with needles and a local application of buffered formic acid and neutralised sodium carbonate. High-resolution computed tomography and post-analysis using the invert ramp option in VGStudio Max 2.0 produced the best results to see the complete skeleton of this specimen. The specimen is distinguishable from the only other known 3D preserved fossil rhinobatoid, the Lower Cretaceous (Albian) genus †Iansan, and is probably a member of Platyrhinidae. [ABSTRACT FROM AUTHOR]