Mineralized skeletal tissue in sharks and rays (Elasmobranchii) and the evolution of tessellated cartilage in cartilaginous fishes. By compiling and comparing recent ultrastructure data on tesserae, we also provide a synthesized, up-to-date and comparative glossary on tessellated cartilage, as well as a perspective on the current state of research into the topic, offering benchmark context for future research into modern and extinct vertebrate skeletal tissues.īiomineralization cartilaginous fish tessellated cartilage tesserae vertebrate endoskeleton. Chimaera monstrosa's tesserae, however, appear to lack the internal cell networks that characterize tesserae in elasmobranchs, indicating fundamental differences among chondrichthyan groups in how calcification is controlled. Liesegang lines, hypermineralized 'spokes'), reflecting periodic accretion of mineral at tesseral edges as tesserae grow.

For example, Chimaera tesserae, like those of elasmobranchs, possess both intertesseral joints (unmineralized regions, where fibrous tissue links adjacent tesserae) and recurring patterns of local mineral density variation (e.g. Tesserae in Chimaera monstrosa are less regular in shape and size in comparison to the general scheme of polygonal tesserae in sharks and rays, yet share several features with them.

We show for the first time that tessellated cartilage was not lost in chimaera, as has been previously postulated, and is in many ways similar to that of sharks and rays. Tesserae have, however, never been demonstrated in modern chimaera and it is debated whether the skeleton mineralizes at all. An accepted uniting character of modern cartilaginous fishes (sharks, rays, chimaera) is the presence of a mineralized, skeletal crust, tiled by numerous minute plates called tesserae.

Chimera fish