Homology of Ethmoidal Ossifications in Neopterygians (Actinopterygii)

LÓPEZ-ARBARELLO, ADRIANA; SFERCO, EMILIA; MIRANDE, JUAN MARCOS

Praga

Congreso; 12th International Congress of Vertebrate Morphology; 2019

Different ossifications have been identified in the ethmoidal region of teleosts: lateral ethmoids, supraethmoid, ventral ethmoid, anterior myodome bone, rostral, lateral dermethmoids and vomer. The single mesethmoid of most teleosts is a compound of two or more of these bones. Some fossil teleosts have a compound rostrodermethmoid. In holosteans, only lateral ethmoids, preethmoids, rostral and vomers have been identified. However, the homology between the nasal processes of the premaxillae of holosteans and the lateral dermethmoids of teleosts has been proposed. Although the homologies, as well as the chondral or dermal origin of these ethmoidal ossifications has been discussed by several authors, no consensus has been achieved and the teleost mesethmoid is usually treated as homologous between different lineages. After thorough survey of the literature and revision of the morphology, topological relationships and ontogeny of these ethmoidal ossifications, we evaluate hypotheses of homology and propose characters for comprehensive cladisticanalyses of the Actinopterygii including also recent taxa. We accept the primary homology between nasal processes and lateral dermethmoids and between preethmoids and ventral ethmoid. The compound rostrodermethmoid includes the rostral and lateral dermethmoids, but probably also a supraethmoid. The composition of the teleost mesethmoid varies in different groups involving two or more of the following elements: supraethmoid, ventral ethmoid, rostral, and lateral dermethmoids. Therefore, independent characters are proposed for each condition. These characters are defined in a way that they should serve to test the hypotheses of primary homology and trace the evolutionary history of each of the actinopterygian ethmoidal ossifications.