Re-examination of the fine structure of endoskeletal mineralization in Chondrichthyans: Implications for growth, ageing and calcium Homeostasis

Abstract

This paper presents a review of the literature describing calcium regulation mechanisms of chondrichthyans, with particular emphasis being given to implications for the nature of the skeleton. A further review of the literature describing mineralized skeletal tissues explores the many conflicting claims about the presence or absence of bone in chondrichthyans. The fine structure of axial and appendicular mineralized tissues from five genera is then described, and evidence is presented to support or refute the hypotheses of others concerning the presence of bone, turnover in the skeleton, and growth without resorption.