INVESTIGADORES
EZCURRA Martin Daniel
congresos y reuniones científicas
Título:
The multiple embryonic origin of the articular and coronoid in mesoeucrocodylian crocodyliforms
Autor/es:
10. BONA P., FERNANDEZ BLANCO M.V., EZCURRA M.D., VON BACZKO M.B., DESOJO J.B., POL D.
Reunión:
Congreso; 34º JAPV; 2021
Resumen:
The lower jaw of early tetrapods is composed of several dermal ossifications. However, a tendency towards the independent reduction of the number of bones has been observed in the mandible of mammals, lepidosaurs, turtles, crocodiles, and birds. Regarding archosaurs, the coronoid and prearticular bones are interpreted to be lost during the evolution of stem-birds and stem-crocodiles, respectively, but the homology of the post-dentary bones retained in living archosaurs remains unclear. Here, we combine palaeontological and embryological evidence to explore the deep homology of the crocodylian post-dentary bones. We study the mandible embryogenesis on a sample of 72 embryos of Caiman and analyse the mandibular transformation along the pseudosuchian phylogeny. In the pre-hatching ontogeny of caimans, at least five dermal ossification centres appear along the margins of the internal mandibular fenestra (perifenestral centres) and, subsequently, merge to form the coronoid (three centres), angular (one centre), and articular (a dermal and a chondral centre). In the fossil record, an independent prearticular is lost around the base of Mesoeucrocodylia (optimized as reappearing in Thalattosuchia when they are placed within Neosuchia), and the coronoid is apomorphically lost in notosuchians. The integration of embryological and palaeontological data indicates that most perifenestral centres are involved in the origin of the prearticular of non-mesoeucrocodylian pseudosuchians. However, these centres are rearranged during evolution to contribute to different post-dentary bones in mesoeucrocodylians. The multi-origin of the post-dentary bones in Crocodylia bolster the idea that the coronoid and the articular are not completely homologous to those of other diapsids.