摘要：SummaryWe resolve debate over the evolution of vertebrate hypermineralized tissues through analyses of matrix protein-encoding secretory calcium-binding phosphoprotein (SCPP) genes and phylogenetic inference of hypermineralized tissues. Among these genes,AMBNandENAMare found in both sarcopterygians and actinopterygians, whereasAMELandSCPP5are found only in sarcopterygians and actinopterygians, respectively. ActinopterygianAMBN,ENAM, andSCPP5are expressed during the formation of hypermineralized tissues on scales and teeth: ganoin, acrodin, and collar enamel in gar, and acrodin and collar enameloid in zebrafish. Our phylogenetic analyses indicate the emergence of an ancestral enamel in stem-osteichthyans, whereas ganoin emerged in stem-actinopterygians and true enamel in stem-sarcopterygians. Thus,AMBNandENAMoriginated in concert with ancestral enamel,SCPP5evolved in association with ganoin, andAMELevolved with true enamel. Shifts in gene expression domain and timing explain the evolution of different hypermineralized tissues. We propose that hypermineralized tissues in osteichthyans coevolved with matrix SCPP genes.Graphical AbstractDisplay OmittedHighlights•Ganoin emerged in actinopterygians; true enamel arose in sarcopterygians•Dental enamel, acrodin, and enameloid in actinopterygians are related to ganoin•SCPP5evolved in association with ganoin, whereasAMELevolved with true enamel•Shifts in SCPP gene expression explain the evolution of hypermineralized tissuesEvolutionary Biology; Evolutionary Processes; Phylogenetics; Paleobiology
