The morphology of the articular region of the pectoral girdle and associated basals in Etmopteridae is revised in light of new evidence provided by taxa unavailable for previous studies. Such studies considered that etmopterids plesiomorphically had a single pectoral articular condyle, and only Etmopterus had two separate ones. Our reanalysis indicates that the possession of two separate condyles, one for the articulation of the propterygium and the second for the meso‐ and metapterygium, is the most widespread condition in this group. However, the presence of two separate articular condyles is not recovered as a synapomorphy for Etmopteridae. Previous studies also proposed that etmopterids lack a hook‐like process on the anteroproximal margin of the anteriormost pectoral basal. We document that the hook‐like process is plesiomorphically present in Etmopteridae, thus corroborating the hypothesis of closer relationships between this family and the other squaliforms that also share this process, namely Centrophoridae, Dalatiidae, Oxynotidae, and Somniosidae.

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Potamotrygon marquesi, sp. nov., is described and compared with other species of Potamotrygon occurring in the Amazon Basin. The identity of this new species is supported by an extensive external and internal morphological study including coloration pattern, squamation, skeleton and ventral lateral‐line canals. Morphometrics and meristics were used to further distinguish P. marquesi from congeners. Potamotrygon marquesi was first considered to fall within the range of variation found in P. motoro. However, even with an extensive variation in coloration observed in P. motoro, this new species presents a series of autapomorphies that confidently distinguishes it from what is understood as the morphological variation found in P. motoro. Additional morphological characters that diagnose P. marquesi include three angular cartilages, asymmetrical star‐shaped denticles, a single regular row of spines on tail dorsum, lateral row of caudal spines near the sting insertion, dorsal disc background in beige and grey mixed with shades of grey and bearing open and closed bicolored rings, among others. Although presenting a gap of distribution along the west–east extension of the Amazon Basin, its diagnostic charactistics are consistent in both recorded regions. Our study supports the need for many morphological characters to robustly distinguish members of Potamotrygoninae considering their extremely variable dorsal disc color pattern.

We report deformities in the pelvic fin and clasper skeleton in specimens of Potamotrygon marquesi from Acre, Northwestern Brazil. The malformations involve skeletal deformities in the pelvic girdle, right clasper skeleton, and severe muscular and skeletal deformities in the left or right pelvic fin and clasper, including the loss of all of its terminal components. Descriptions of malformations dealing with elasmobranchs are extensive in the literature and are important for future studies dealing with their probable causes. Nevertheless, although the reasons of these deformities are herein possibly linked to malformation (as a result of stress or chemical contaminants) or predation, the anomalies in the muscular and skeletal components of the pelvic fin and clasper are described in detail and compared to a non‐deformed specimen.

Agradeço primeiramente aos meus pais João Paulo Batista da Silva e Cacilda Capretz Batista da Silva, por seu amor, companheirismo, amizade e todo suporte necessário, imprescindíveis para realização deste trabalho. Agradeço também as minhas irmãs Nancy Capretz Batista da Silva e Juliana Capretz Batista da Silva por seu afeto e apoio em todas as etapas do meu trabalho. Ao meu orientador e amigo, Prof. Dr. Marcelo R. de Carvalho pelo conhecimento transmitido e por me ceder mais uma vez a oportunidade de trabalhar com um grupo tão intrigante de elasmobrânquios.

The rays of the order Myliobatiformes present several diagnostic characters, the most striking one being the presence of a serrated sting on the dorsal region of the tail. Although several morphological hypotheses have been proposed supporting the monophyly and interrelationships of its members, few characters of the appendicular skeleton were employed. In the present study, we analyzed comparatively the pelvic girdle morphology across all the groups of rays to investigate the distribution of the ischial process. To understand its significance, we tested this character of the pelvic girdle as a potential synapomorphy for the Myliobatiformes plus Zanobatus. Accordingly, the phylogenetic position of Zanobatus as a sister taxon to Myliobatiformes is reinforced and its pelvic girdle morphology reinterpreted in relation to previous morphological studies.

Lamniform sharks are one of the more conspicuous groups of elasmobranchs, including several emblematic taxa as the white shark. Although their monophyly is well supported, the interrelationships of taxa within Lamniformes remains controversial because of the conflict among various previous molecular‐based and morphology‐based phylogenetic hypotheses. In this study, we use 31 characters related to the appendicular skeleton of lamniforms and demonstrate their ability to resolve the systematic interrelationships within this shark order. In particular, the new additional skeletal characters resolve all polytomies that were present in previous morphology‐based phylogenetic analyses of lamniforms. Our study demonstrates the strength of incorporating new morphological data for phylogenetic reconstructions.

A new species of congrid eel, Bathycongrus villosus sp. nov., is described from the Philippines and Vanuatu. It is similar to some of the small-toothed species currently placed in Bathycongrus and to the species of Bassanago. In this paper we compare the new species to Bassanago albescens (Barnard, 1923) and to Bathycongrus parviporus Karmovskaya, 2011, which it most closely resembles. An analysis of 19 characters shows that it agrees with Bat. parviporus in 16 characters and with Bas. albescens in one. In two characters, the three species are all different. We therefore place it in Bathycongrus.