The presence of collagen in enameloid distinguishes it clearly from true enamel, but little is known about the
phylogenetic relationship between these 2 tissues. It has previously been reported that amelogenins are the
principal proteins of the enamel matrix, that type I collagen and chondroitin sulphates are the predominant
matrices in dentine, and that amphibian and reptilian aprismatic enamels contain no sulphated
glycoconjugates, although certain sulphated substances are secreted into mammalian prismatic enamel
during matrix formation. The larval urodele (Triturus pyrrhogaster) teeth are known to be composed of
enameloid, dentine, and enamel-like tissue. To characterise the tooth matrices, the localisation of
amelogenin-like proteins, type I collagen, and sulphated glycoconjugates was investigated. Chondroitin
sulphates and fine fibrils immunoreactive for type I collagen were elaborated as the enameloid matrix inside
the dental basement membrane. After the matrix had been deposited in full thickness, coarse collagen fibrils
also immunoreactive for type I collagen and chondroitin sulphates were deposited below as the first dentine
matrix. Further, enamel-like matrix with no collagen fibrils or sulphated glycoconjugates but strongly
immunoreactive for amelogenins was deposited on the dentine. Although no immunolabelling for
amelogenins was found over the enameloid matrix, at least at the formation stage, the zone of coarse
collagen fibrils of dentine was partially immunoreactive as observed in mammalian mantle dentine. From the
ontogeny and matrix constituents of larval urodele teeth, it is suggested that enameloid is originally a
dentine-like tissue.