Dental replacement in Mesozoic birds: evidence from newly discovered Brazilian enantiornithines

WU, YUN-HSIN; CHIAPPE, LUIS M.; BOTTJER, DAVID J.; NAVA, WILLIAM; MARTINELLI, AGUSTÍN G.

Scientific Reports

Nature

Año: 2021 vol. 11

Polyphyodonty?multiple tooth generations?in Mesozoic birds has been confrmed since thenineteenth century. Their dental cycle had been assessed through sparse data from tooth rootsrevealed through broken jawbones and disattached teeth. However, detailed descriptions of theirtooth cycling are lacking, and the specifcs of their replacement patterns remain largely unknown.Here we present unprecedented µCT data from three enantiornithine specimens from the UpperCretaceous of southeastern Brazil. The high resolution µCT data show an alternating dentalreplacement pattern in the premaxillae, consistent with the widespread pattern amongst extinctand extant reptiles. The dentary also reveals dental replacement at diferent stages. These resultsstrongly suggest that an alternating pattern was typical of enantiornithine birds. µCT data show thatnew teeth start lingually within the alveoli, resorb roots of functional teeth and migrate labially intotheir pulp cavities at an early stage, similar to modern crocodilians. Our results imply that the controlmechanism for tooth cycling is conserved during the transition between non‑avian reptiles and birds. These first 3D reconstructions of enantiornithine dental replacement demonstrate that 3D data are essential to understand the evolution and deep homology of archosaurian tooth cycling.