Osteology of the White Barracudina, Arctozenus risso (Bonaparte) (Aulopiformes: Paralepididae)

Abstract

Arctozenus risso, the White Barracudina, is a member of the Paralepididae, the largest family within the order Aulopiformes. In recent years the systematics of the family and the order has advanced significantly due to morphological, molecular, and holistic studies, which has led to a general agreement of their relationships. Some phylogenetic discrepancies remain in particular among the species-rich paralepidids, based on the difficulties in obtaining comprehensive taxon samples as well as the lack of morphological studies. We found an enlarged autopalatine following the enlarged ethmoid region of the skull. We identified a large ossification that covers the dorsal surface of the basibranchial copula as a basibranchial tooth plate and identified a second smaller tooth plate associated with basibranchial 4. However, the most peculiar structures are dorsal ligament ossifications that are associated with the anterior and posterior dorsal-fin pterygiophores, and supraneural 2. We hope the description of the skeletal anatomy of A. risso will help to solve some of the open questions of the phylogenetic relationships of the paralepidids and aulopiforms.