Dental morphology and replacement pattern of Late Cretaceous Brazilian enantiornithine birds.

WU, Y. -H; LUIS CHIAPPE; BOTTJER, D.J.; NAVA, WILLIAM R.; MARTINELLI, AGUSTÍN G.

Brisbane

Congreso; 79th Annual Meeting, Society of Vertebrate Paleontology; 2019

SVP

The occurrence of polyphyodonty?multiple generations of toothreplacement?in Mesozoic birds has been known since the 19th century, yetthis phenomenon has only been investigated superficially. For example, it hasnot been known whether stem birds had the same alternating pattern as theirnon-avian dinosaur relatives, and whether this kind of dental replacementpattern is conserved in archosaurs. With the purpose of investigating thesequestions, an enantiornithine premaxilla (MPM 90, Museu de Paleontologiade Marília) and a partial dentary (MPM 351) from the Upper CretaceousAdamantina Formation of southern Brazil were μCT scanned at 3 μmresolution. The results show preservation of replacement teeth and their toothfamilies. 3D reconstruction of the replacement tooth rows shows a conservedalternating pattern as seen in other archosaurs. In addition, we apply a newmorphologic framework (quantitative and qualitative) for organizing toothdiversity in enantiornithines. Using parameters such as crown base length,crown height, apical length, curvature, enamel ornamentation, number of teethon each tooth-bearing bone, and dental spacing, the dental anatomy of the twoBrazilian specimens clusters together with that of other enantiornithine toothmorphotyes. In sum, we show that the alternating tooth replacement patternof toothed birds is shared with that of crocodilians, indicating a conservedpattern in archosaurs. Our results thus imply a conserved underlying controlmechanism for this pattern of tooth cycling. The characters we used to analyzethe range of dental morphology in enantiornithines provide a morphologicframework that can be applied to other toothed avian clades in order tounderstand dental evolution in stem birds.