Dental ontogeny in the most primitive bony fishLophosteusreveals the developmental relationship between teeth and dermal odontodes

Abstract

Ontogenetic data obtained by synchrotron microtomography of a marginal jawbone of Lophosteus superbus (Late Silurian, 422 Million years old), the phylogenetically basalmost stem osteichthyan, reveal developmental relationships between teeth and ornament that are not obvious from the adult morphology. The earliest odontodes are two longitudinal founder ridges formed at the ossification center. Subsequent odontodes that are added lingually to the ridges turn into conical teeth and undergo cyclic replacement, while those added labially achieve a stellate appearance. The stellate odontodes deposited directly on the bony plate are aligned with the alternate files of the teeth. Successive odontodes overgrowing the labial tooth rows become tooth-like and the replacement teeth near to them are ornament-like. We propose that teeth and ornament are modifications of a single odontode system regulated and differentiated by the oral and dermal signals; signal cross-communication between the two domains can occur around the oral-dermal boundary.

A Bayesian approach to dynamic homology of morphological characters and the ancestral phenotype of jawed vertebrates

“…Facial laminae were subsequently lost in core placoderms and palatal laminae were lost in osteichthyans. The stem osteichthyans Lophosteus and Andreolepis show a possibly intermediate condition, in which the marginal jaw bones have internal (oral or palatal) laminae that are more strongly developed compared to other osteichthyans ( Botella et al, 2007 ; Cunningham et al, 2012 ; Chen et al, 2016 ; Chen et al, 2020 ).…”