CNRS UMR 5242 Institut de Génomique Fonctionnelle de Lyon, Team Evo devo of vertebrate dentition, Université de Lyon, ENS de Lyon, 69364, Lyon cedex, 07, France.
Université de Lyon, UCBL, ENSL, CNRS, UMR 5276 LGL-TPE, 69622, Villeurbanne, France.
Sci Rep. 2018 Aug 28;8(1):12952. doi: 10.1038/s41598-018-31022-3.
Modern birds (crown group birds, called Neornithes) are toothless; however, the extinct neornithine Odontopterygiformes possessed bone excrescences (pseudoteeth) which resembled teeth, distributed sequentially by size along jaws. The origin of pseudoteeth is enigmatic, but based on recent evidence, including microanatomical and histological analyses, we propose that conserved odontogenetic pathways most probably regulated the development of pseudodentition. The delayed pseudoteeth growth and epithelium keratinization allowed for the existence of a temporal window during which competent osteoblasts could respond to oral epithelial signaling, in place of the no longer present odontoblasts; thus, bony pseudoteeth developed instead of true teeth. Dynamic morphogenetic fields can explain the particular, sequential size distribution of pseudoteeth along the jaws of these birds. Hence, this appears as a new kind of deep homology, by which ancient odontogenetic developmental processes would have controlled the evolution of pseudodentition, structurally different from a true dentition, but morphologically and functionally similar.
现代鸟类（冠群鸟类，称为新鸟）没有牙齿；然而，已灭绝的新鸟形目 Odontopterygiformes 拥有类似于牙齿的骨质突起（假齿），沿着颌骨大小顺序分布。假齿的起源是神秘的，但基于最近的证据，包括微观解剖学和组织学分析，我们提出保守的牙发生途径很可能调节了假齿的发育。假齿的生长和上皮角蛋白化的延迟，使得在一个暂时的窗口期间，有能力的成骨细胞可以对口腔上皮信号做出反应，而不是不再存在的成牙质细胞；因此，骨质假齿而不是真正的牙齿发育。动态形态发生场可以解释这些鸟类颌骨上假齿的特定、顺序的大小分布。因此，这似乎是一种新的深层同源性，通过这种同源性，古老的牙发生发育过程控制了假齿的进化，假齿在结构上与真正的牙齿不同，但在形态和功能上相似。
