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Systematics of the genus Scyliorhinus Blainville, 1816 (Chondrichthyes: Carcharhiniformes: Scyliorhinidae)

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Author(s):
Karla Diamantina de Araújo Soares
Total Authors: 1
Document type: Doctoral Thesis
Press: São Paulo.
Institution: Universidade de São Paulo (USP). Instituto de Biociências (IBIOC/SB)
Defense date:
Examining board members:
Mônica de Toledo Piza Ragazzo; Rodrigo Antunes Caires; Otto Bismarck Fazzano Gadig; Ulisses Leite Gomes; Alessio Datovo da Silva
Advisor: Mônica de Toledo Piza Ragazzo
Abstract

The genus Scyliorhinus belongs to the family Scyliorhinidae, the most diverse family of sharks, and to the subfamily Scyliorhininae, with Cephaloscyllium and Poroderma. There are currently 16 valid species for Scyliorhinus, however many questions are raised concerning the definition and composition of the genus, mainly regarding the identity of S. canicula. Furthermore, the long history of taxonomic rearrangements and inaccurate descriptions of many species have contributed to misidentification of specimens and lack of information on the distribution range and diagnostic characters of many species. This study aimed to review the taxonomy of the genus and to estimate the geographic distribution of all its species. In addition, the phylogenetic relationships of the Scyliorhinus species within the subfamily Scyliorhininae was investigated. Specimens of all Scyliorhinus species were examined as well as specimens of four species of Cephaloscyllium spp., two species of Poroderma spp. and representatives of almost all other catshark genera. A detailed morphological study, including external morphology, internal anatomy, morphometry and meristic data, were performed. From this study, a total of 77 mophological and three meristic characters were compiled into a matrix. Parsimony analysis was employed to generate hypotheses of phylogenetic relationships using the TNT 1.1 computer program. Asymbolus analis was used to root the cladogram. The analysis of the phylogenetic relationships based on implied weighting (k = 3; 500 replications and 100 trees saved per repl.) resulted in seven equally most parsimonious cladograms with 231 steps, with a CI of 0.42 and an RI of 0.69. The monophyly of the subfamily Scyliorhininae is supported on the basis of the absence of the muscle depressor palpebrae nictitans as well as of the bifurcation on the leading edge of basihial cartilage and accessory marginal cartilage on the claspers, a lower number of ventral extra branchial cartilages, a greater extension of the dermal terminal cover on the clasper and short clasper siphons. The monophyly of Scyliorhinus is supported on the basis of the presence of a projecting tab at upper lip margin as well as of a pelvic apron and a greater extension of it. Scyliorhinus is proposed as the sister group of Cephaloscyllium, based on the presence of processus rastriformis similar in length and a welldeveloped medial projection of the coracoid bar. The phylogenetic relationships among Scyliorhinus species are presented for the first time. In this study, 16 species are recognized: Scyliorhinus boa, S. cabofriensis, S. canicula, S. capensis, S. cervigoni, S. comoroensis, S. duhamelli, S. garmani, S. haeckelii, S. hesperius, S. meadi, S. retifer, S. stellaris, S. torazame, S. torrei, and S. ugoi. The main taxonomic decisions include the resurrection of S. duhamelii and the synonimization of S. tokubee with S. torazame. The information of the geographic distribution was updated for most species, especially for those with wide ranges (S. canicula, S. haeckelii, S. retifer and S. stellaris). Coloration, vertebral counts, clasper morphology, maturity size and configuration of nasal flaps are the most useful characters to distinguish among species (AU)

FAPESP's process: 14/20316-5 - Taxonomy and morphology of genus Scyliorhinus Blainville, 1816 (Chondrichthyes: Carcharhiniformes: Scyliorhinidae)
Grantee:Karla Diamantina de Araújo Soares
Support Opportunities: Scholarships in Brazil - Doctorate