Phylogeny of the major groups of Chondrichthyes based on the comparative anatomy of the skeleton of the paired fins and girdles

Author(s)

João Paulo Capretz Batista da Silva

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Biociências (IBIOC/SB)
• Defense date: 2014-12-18

Examining board members

Marcelo Rodrigues de Carvalho; Ulisses Leite Gomes; Mônica de Toledo Piza Ragazzo; Alessio Datovo da Silva

• Advisor: Marcelo Rodrigues de Carvalho

Abstract

Fishes of the class Chondrichthyes correspond to an ancient and well-succeeded group that has demonstrated significant modifications in the skeletal structures of the paired fins from the Paleozoic to the present day. A thorough anatomical analysis based on the appendicular skeleton of Chondrichthyes was realized and raised new skeletal characters with phylogenetic implications. The skeletal structure of paired fins is a complementary tool in the resolution of still debated phylogenetic questions within the class, such as the controversy involving the monophyly of sharks and the phylogenetic positioning of rays. In the present study, 154 taxa were analyzed exposing details of the morphology and arrangement of radials, basals and pectoral and pelvic girdles. In addition, two phylogenetic analyses were conducted based on 105 characters proposed from the observed skeletal patterns of paired fins and data from the literature. Some previous relationships explored in morphological and molecular studies were recovered herein, such as the monophyly of several orders of elasmobranchs, the sister-group relationship between Heterodontiformes and Orectolobiformes, the sister group relationship between Zanobatus and Myliobatiformes, besides a greater support to the recently proposed clade Rhinopristiformes. However, the hypnosqualean group was not recovered in the present study, although the sharks were resolved as paraphyletic and presenting a new sister group relationship with the batoids. Additionally, new characters related to the appendicular skeleton were suggested as derived for the Holocephali, but they must be tested as potential synapomorphies in future phylogenetic analysis (AU)