Systematic implications of the caudal fin skeletal anatomy in ground sharks, order Carcharhiniformes (Chondrichthyes: Elasmobranchii)

• Published in: Zoological journal of the Linnean Society Vol. 185; no. 1; pp. 193 - 211
• Main Authors: Moreira, Renan A, Gomes, Ulisses L, de Carvalho, Marcelo R
• Format: Journal Article
• Language: English
• Published: UK Oxford University Press 01-01-2019
• Subjects: Animal behavior; Carcharhinidae; Carcharhiniformes; Fins; Marine fishes; Phylogeny; Scyliorhinidae; Sharks; Skeleton; Sphyrna lewini; Sphyrna tiburo; Sphyrna tudes; Sphyrna zygaena; anatomy; morphological comparison; caudal skeleton
• ISSN: 0024-4082; 1096-3642
• DOI: 10.1093/zoolinnean/zly038

Abstract
Sharks typically have a heterocercal tail, with both epaxial and hypaxial skeletal elements. The epaxial elements are composed of supraneural spines and neural arches (basidorsals and interdorsals); the hypaxial elements are basiventrals (forming the haemal arches) and haemal spines, as well as a series of prehypochordal cartilages found only in Galeocerdo. The tail of carcharhiniform sharks, except Scyliorhinidae, can be divided into anterior and posterior diplospondylic caudal regions. The anterior diplospondylic caudal region is characterized by haemal spines detached from basiventrals. The posterior diplospondylic caudal region has all haemal spines continuous with the basiventrals. In carcharhiniform sharks, the caudal fin skeleton can be divided into four main morphological types: scyliorhinoid (Scyliorhinidae), triakoid (Triakidae, Chaenogaleus and Paragaleus), carcharhinoid (Hemipristis, Hemigaleus, Carcharhinidae, Sphyrna tiburo and Sphyrna tudes) and eusphyrnoid (Eusphyra, Sphyrna lewini and Sphyrna zygaena). The carcharhinoid caudal fin type supports the monophyly of the clade Carcharhinidae and Sphyrnidae and is present in the hammerhead sharks with a relatively small cephalofoil that are phylogenetically basal within sphyrnids. The eusphyrnoid caudal fin type is the more derived pattern for Carcharhiniformes.