Osteology of the telescopefishes of the genusGigantura(Brauer, 1901), Teleostei: Aulopiformes

The two species of the family Giganturidae are highly derived aulopiform fishes that inhabit the mesopelagic realm of the oceans. Giganturids are exceptionally modified morphologically and, in particular, are characterized by numerous skeletal reductions that render the identification of the remaining elements problematic. The most debated of these are the toothed elements of the upper jaw, which have played a significant role in hypotheses about the phylogenetic affinities of the family. The largest toothed element of the upper jaw has been considered to be the premaxilla (the general consensus for the last four decades), a fused premaxilla and maxilla, or the palatine. The goal of this paper is to provide a detailed description of the osteology of adult giganturids to resolve the identification and homology of skeletal elements, particularly those of the upper jaw. Based on topological evidence, we conclude that the premaxilla is absent and that the major tooth-bearing bone in the ‘upper jaw’ is the palatine.