Revisão das raias viola (Chondrichthyes: Rhinopristiformes) do Atlântico sul ocidental

Abstract

The guitarfish from south-western Atlantic embrace three species: Pseudobatos horkelii, Pseudobatos percellens e Zapteryx brevirostris. They have undergone through recent taxonomic changes: the order has changed from Rhinobatiformes to Rhinopristiformes; both of Pseudobatos were Rhinobatos; and now Zapteryx is arranged inside of the family Trygonorrhinidae. Some evident caracteristics of this group are: robust caudal region, welldevelopped rostral cartilage and elongated body shape. Those taxonomic changes have been proposed by recent phylogenetic and molecular studies, especially based on the oronasal morphology. This morphology is conserved among the genus but differs in the whole order; therefore, there are still unsolved taxonomic problems inside the group. Furthermore, the morphology of P. horkelii and P. percellens is extremely similar, some scientists even considering to be only one species, and for studies and works of preservation and conservation, the accurate identification of species is crucial, especially in the case of P. horkelii, which is critically endangered according to the IUCN criteria. The following study had as aims: I) to presente an anatomical redescription of the three nominal species of guitarfish found in the Brazilian coast; II) to test the validity of Brazilian Pseudobatos species, through morphological techniques; and III) to propose a diagnosis for the Brazilian taxa based in morphological data. The used material was accrued from the association of the fishermen of Itaipu and Copacabana beaches (by donation of their fishery), which has undergone through preparation by dermestidae coleoptera, from previously diaphanised and laid up in UERJ collection specimen and from the lookup at the Pseudobatos spp. collection from the National Museum of UFRJ. For the differentiation of the external morphology between P. horkelii and P. percellens, just one character (previously described in litterature) was considered valid: the oval dark blot on the ventral surface of the rostrum portion. However, it was found a new character for the differentiation of both species in inner morphology: the insertion of two rays of the pectoral fin directly in the pectoral girdle in P. percellens and the insertion of only one ray in P. horkelii. It was not found sexual dimorphism between Pseudobatos spp., unlike Z. brevirostris, and the it was seen starting in juvenile stage. In the ontogenetic analysis there was a change in the whole body shape, originated mainly from the rostrum elongating, migration of the eye sockets to the dorsal surface and extension of the pectoral propterygium and metapterygium. It was also seen that P. percellens acquires calcification prior to P. horkelii. Z. brevirostris has shown more intraspecific variation than Pseudobatos spp., mainly in pectoral and pelvic fins. The description of the skeletal-anatomical complex for the three species can be considered successful, thus, the three species have had their validity confirmed; however, for better knowledge of their biology there are still needed plenty of studies. As the three species are endangered, more detailed studies of the systematic, anatomy and biology are important to help in their conservation and preservation.