Estudo comparativo do neurocrânio de duas espécies da família Squalidae: Cirrhigaleus asper (Merret, 1973) e Squalus acanthias Linnaeus, 1758 (Elasmobranchii: Squaliformes)

Abstract

The neurocranium of sharks represents a valuable source of phylogenetic information due to its morphological plasticity . For this reason, an in-depth anatomical analysis of the neurocranium of two representatives of the family Squalidae (Elasmobranchii: Squaliformes), Cirrhigaleus asper and Squalus acanthias, was carried out with the aim of raising morphological characters that could be used in future phylogenetic analyses, helping to understand the interrelations of this group, which presents several controversies. From the analysis of the neurocrania deposited in the UFPB's ichthyological collection and images sent by a collaborator , it was possible to conduct a detailed comparative description of these structures. A third species within Squaliformes (Centrophorus granulosus) was used as an outgroup. T wenty primary homologies could be tested and confirmed as apomorphies: eight of them as synapomorphies supporting the monophyly of the family Squalidae and seven were recovered as autapomorphies for Cirrhigaleus. This preliminary result supports the placement of the species S. acanthias and C. asper into distinct genera and goes against the placement of C. asper in the genus Squalus, as suggested by recent molecular studies. The present study also contributes initially to solving the problem raised by V iana (2016) that it is necessary to propose a robust phylogenetic analysis using a series of morphological characters that may help solve the internal relationships of Squalidae. In the future, it is expected to expand the number of characters of the neurocranium and of the terminal taxa analyzed in order to propose a more comprehensive phylogeny for members of the family Squalidae as well as for other taxa in Squaliformes.