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Dental replacement in Mesozoic birds (1 Viewer)

Fred Ruhe

Well-known member
Netherlands
Yun‑Hsin Wu, Luis M. Chiappe, David J. Bottjer, William Nava & Agustín G. Martinelli, 2021

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

Scientific Reports. 11 (1): Article number 19349.
doi:10.1038/s41598-021-98335-8

Abstract and free pdf: https://www.nature.com/articles/s41598-021-98335-8.pdf

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

Enjoy,

Fred
 

Fred Ruhe

Well-known member
Netherlands
Figure 1. Photographs of the enantiornithine specimens MPM-90, MPM-373, and MPM-351, and a simplifed cladogram highlighting the stem avian taxa discussed in this study. MPM-373: (a) dorsal view; (b) right lateral view; (c) lef lateral view. MPM-90: (d) dorsal view; (e) right lateral view. MPM-351: (f) lef lateral view. En external nares, Fp frontal process

Figure 2. Dentition of MPM-90, MPM-373, and MPM-351 visualized through μCT imaging. (a–c) Labial views; (a′, a″, b′, b″, c′, c”) cross-sections of replacement teeth at the 1st (a′–c′), 2nd (c″) and 4th (a″, b″) positions. This figure was created to demonstrate the tooth distribution within jawbones and the resorption between the functional and replacement teeth. (a) Right lateral view of MPM-90, digitally flipped for comparison. (b) Left lateral view of MPM-373. (c) Left lateral view of MPM-351. Functional teeth in cyan; replacement teeth in magenta. Note that the functional teeth generally have more resorption on their lingual sides, except at the 4th tooth position of the right premaxilla of MPM-90 (a″). Rt replacement tooth, La labial, Li lingual.

Fred
 

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