title: Palaeobiology: calcification of early vertebrate cartilage.
abstract: Hagfish and lampreys are unusual for modern vertebrates in that they have no jaws and their skeletons are neither calcified nor strengthened by collagen   the cartilaginous elements of their endoskeleton are composed of huge, clumped chondrocytes (cartilage cells). We have discovered that the cartilage in a 370-million-year-old jawless fish, Euphanerops longaevus, was extensively calcified, even though its cellular organization was similar to the non-mineralized type found in lampreys. The calcification of this early lamprey-type cartilage differs from that seen in modern jawed vertebrates, and may represent a parallel evolutionary move towards a mineralized endoskeleton.
authors.affiliation: CNRS, UMR 8569, Muséum National d'Histoire Naturelle, 75231 Paris Cedex 05, France. janvier@mnhn.fr
authors.forename: Philippe
authors.initials: P
authors.lastname: Janvier
authors.forename: Marius
authors.initials: M
authors.lastname: Arsenault
mesh_terms: D000818:Animals; D005075:Biological Evolution; D002113:Calcification, Physiologic; D002118:Calcium / Q000378:metabolism; D002356:Cartilage / Q000166:cytology / Q000378:metabolism; D019902:Chondrocytes / Q000378:metabolism; D005399:Fishes / Q000033:anatomy & histology* / Q000502:physiology*; D005580:Fossils; D007798:Lampreys / Q000033:anatomy & histology* / Q000502:physiology*
chemical_list: D002118:Calcium