Recent insights into the morphological diversity in the amniote primary and secondary palates. Issue 12 (10th September 2015)

• Record Type: Journal Article
• Authors: Abramyan, John; Richman, Joy Marion
• Is Part Of: Developmental dynamics. Volume 244:Issue 12(2015:Dec.)
• Page Start: 1457
• Page End: 1468
• Publication Date: 2015-09-10
• Subjects: primary palate -- choana -- reptile -- craniofacial -- palatal shelves -- lip fusion; Morphogenesis -- Periodicals; Anatomy -- Periodicals; Anatomie -- Périodiques; Biologie du développement -- Périodiques; 571.833
• DOI: 10.1002/dvdy.24338
• Languages: English
• ISSNs: 1058-8388

Abstract

Abstract : The assembly of the upper jaw is a pivotal moment in the embryonic development of amniotes. The upper jaw forms from the fusion of the maxillary, medial nasal, and lateral nasal prominences, resulting in an intact upper lip/beak and nasal cavities; together called the primary palate. This process of fusion requires a balance of proper facial prominence shape and positioning to avoid craniofacial clefting, whilst still accommodating the vast phenotypic diversity of adult amniotes. As such, variation in craniofacial ontogeny is not tolerated beyond certain bounds. For clarity, we discuss primary palatogenesis of amniotes into in two categories, according to whether the nasal and oral cavities remain connected throughout ontogeny or not. The transient separation of these cavities occurs in mammals and crocodilians, while remaining connected in birds, turtles and squamates. In the latter group, the craniofacial prominences fuse around a persistent choanal groove that connects the nasal and oral cavities. Subsequently, all lineages except for turtles, develop a secondary palate that ultimately completely or partially separates oral and nasal cavities. Here, we review the shared, early developmental events and highlight the points at which development diverges in both primary and secondary palate formation. Developmental Dynamics 244:1457–1468, 2015 . © 2015 Wiley Periodicals, Inc. Key Findings: Amniote primary palate development occurs through two different mechanisms. Crocodilians and mammals share similar mechanisms of primary and secondary palate development. Birds, turtles and lizards share similar primary palate development and differ in secondary palate development. Bony secondary palates have evolved independently in mammals, crocodilians and turtles.