New data on the systematics and interrelationships of sawfishes (Elasmobranchii, Batoidea, Pristiformes)

New characters based on the arrangement and morphology of dermal denticles show that sawfishes can be divided into two distinctive groups. The first group, comprising the knifetooth sawfish Anoxypristis cuspidata, is characterized by tricuspid denticles variably located on both dorsal and ventral parts of the body. The second group is represented by species of the genus Pristis, showing an uniform and homogenous dermal covering of monocuspidate denticles on both dorsal and ventral sides of the body and within the buccopharyngeal cavity. Pristis is further divided into two subgroups: the first comprises species with denticles lacking any keels and furrows (the smalltooth sawfish Pristis pectinata, the green sawfish Pristis zijsron and the dwarf sawfish Pristis clavata); the second comprises species with denticles presenting keels and furrows well differentiated on their anterior part (the common sawfish Pristis pristis, the largetooth sawfish Pristis perotteti and the greattooth sawfish Pristis microdon). This investigation of the dermal covering provides results which agree with studies that separate the same two species groups of Pristis on the basis of other morphological data

Sensory systems in sawfishes. 2. The lateral line

The lateral line system allows elasmobranchs to detect hydrodynamic movements in their close surroundings. We examined the distribution of pit organs and lateral line canals in 4 species of sawfish (Anoxypristis cuspidata, Pristis microdon, P. clavata and P. zijsron). Pit organs could only be located in A. cuspidata, which possesses elongated pits that are lined by dermal denticles. In all 4 pristid species, the lateral line canals are well developed and were separated into regions of pored and non-pored canals. In all species the tubules that extend from pored canals form extensive networks. In A. cuspidata, P. microdon and P. clavata, the lateral line canals on both the dorsal and ventral surfaces of the rostrum possess extensively branched and pored tubules. Based on this morphological observation, we hypothesized that these 3 species do not use their rostrum to search in the substrate for prey as previously assumed. Other batoids that possess lateral line canals adapted to perceive stimuli produced by infaunal prey possess non-pored lateral line canals, which also prevent the intrusion of substrate particles. However, this hypothesis remains to be tested behaviourally in pristids. Lateral line canals located between the mouth and the nostrils are non-pored in all 4 species of sawfish. Thus this region is hypothesized to perceive stimuli caused by direct contact with prey before ingestion. Lateral line canals that contain neuromasts are longest in P. microdon, but canals containing neuromasts along the rostrum are longest in A. cuspidata

An annotated checklist of the fishes of Gabon

International audienceUsing all data sources available, we collected 2,189 nominal scientific names that have been applied to the fishes from Gabon. Data from the literature and online database indicate that 1,062 valid species of fishes live in Gabonese waters, with 288 of these strictly restricted to freshwaters, 592 strictly restricted to marine environments and 182 species euryhaline species. Among the latter one finds 121 species inhabit in both marine and brackish environments, 16 that occur in both freshwater and brackish environments and 45 found in all salinities. These 1,062 species represent 60 orders and 224 families. An additional 202 species, mostly marine, may be present in Gabon although they have not been yet recorded. Endemic species represent 7% (75) of the 1,062 valid described species for Gabon, within just one of these from marine waters and 74 freshwaters species (mostly killifish within the genus Aphyosemion – 33 species). Regarding the IUIUCN status, 135 present (+19 possible) species (12.7%) are considered as endangered (from near threatened to critically endangered), and 135 (+24 possible) (12.7%) species are not evaluated or data deficient. The remaining species are least concern. Continued descriptions of new species from the waters of Gabon demonstrate that the present total most likely underestimates the species level diversity of the fish fauna.En utilisant toutes les sources disponibles des données, nous avons répertorié 2 189 noms scientifiques de poissons du Gabon. Les données de la littérature et des bases de données montrent que 1 062 espèces de poissons sont actuellement connues des eaux du Gabon, avec 288 strictement en eaux douces et 592 strictement marines, 182 espèces sont euryhalines avec 121 connues des eaux marines et saumâtres, 16 des eaux douces et saumâtres et, pour finir, 45 sont trouvées dans tous les milieux, quel que soit la salinité. Ces 1 062 espèces représentent 60 ordres et 224 familles auxquelles il est possible de rajouter 202 espèces, principalement marines, qui sont peut-être présentes au Gabon mais n’y ont pas encore été observées. Les espèces endémiques représentent 7% (75) du nombre des 1 062 espèces décrites et valides du Gabon : une seule espèce marine et 74 espèces des eaux douces (principalement des “killis” du genre Aphyosemion – 33 espèces). À propos du statut de l’IUCN, 135 des espèces présentes (+19 possibles) (12,7%) sont considérées comme en voie de disparition (de quasi-menacées à en danger critique), et 135 (+24 possibles) (12,7%) ne sont pas évaluées ou bien avec des données insuffisantes. Les autres sont de préoccupation mineure. Des descriptions continuelles de nouvelles espèces provenant des eaux du Gabon démontrent que la diversité de la faune des poissons du Gabon est fortement sous-estimée

The biology of extinct and extant sawfish (Batoidea: Sclerorhynchidae and Pristidae)

Sclerorhynchids (extinct sawfishes, Batoidea), pristids (extant sawfish, Batoidea) and pristiophorids (sawsharks, Squalomorphi) are the three elasmobranch families that possess an elongated rostrum with lateral teeth. Sclerorhynchids are the extinct sawfishes of the Cretaceous period, which reached maximum total lengths of 100\ua0cm. The morphology of their rostral teeth is highly variable. Pristid sawfish occur circumtropically and can reach maximum total lengths of around 700\ua0cm. All pristid species are globally endangered due to their restricted habitat inshore. Pristiophorid sawsharks are small sharks of maximum total lengths below 150\ua0cm, which occur in depths of 70–900\ua0m. Close examination of the morphology of pectoral fin basals and the internal structure of the rostrum reveals that sclerorhynchids and pristids evolved independently from rhinobatids, whereas pristiophorids are squalomorph sharks. The elongation of the rostrum may be an adaptation for feeding, as all marine vertebrate taxa that possess this structure are said to use it in the context of feeding