Order POLYMIXIIFORMES (42)—beardfishes. Few groups have been shifted back and forth as frequently as this one, while still being considered of uncertain affinity. The one family is placed within the Beryciformes by many workers employing differing methods. Several works such as Stiassny (1986) and Johnson and Patterson (1993) provided evidence that it is or could be the sister group to all other Acanthomorphs. As noted by Stiassny (1986), Polymixia is unique in having a palato-premaxillary ligament passing between maxillary lateral processes, rather than between contralateral palatines.
Family POLYMIXIIDAE (208)—beardfishes. Marine; tropical and subtropical Atlantic, Indian (primarily off Natal), and western Pacific.
Body moderately elongate and compressed; pair of hyoid barbels; dorsal fin continuous, with 4-6 spines and 26-38 soft rays; anal fin with four short spines and 13-17 soft rays; pelvic fins subabdominal, with one spinelike ray and six soft rays; 16 branched caudal rays; about 33-38 lateral line scales; four bran-chiostegal rays; 11-21 gill rakers; two supramaxillae; subocular shelf, orbitosphenoid, and basisphenoid present; three epurals; usually 29 or 30 vertebrae. This is the only acanthomorph retaining two sets of intermuscular bones, epipleurals (what are generally termed epipleurals in acanthomorphs are now thought to be homologous with the epineurals of lower teleosts— Johnson and Patterson, 1993). Maximum length 38 cm. Beardfishes usually occur between 180 and 640 m.
One genus, Polymixia, with 10 species (e.g., Moore, 2003). Fossils include such Upper Cretaceous genera as Berycopsis, Dalmatichthys, Omosoma, and Omosomopsis.
fOrder CTENOTHRISSIFORMES. Position uncertain. Contains the marine Upper Cretaceous genera Aulolepis and Ctenothrissa. Rosen (1973a) considered it possible that the ctenothrissiforms are the "primitive sister group of the paracanthopterygian-acanthopterygian assemblage" and classified them with that assemblage under the category of Sept Acanthomorpha. Pattersonichthys may bear some distant relationship to Aulolepis and Ctenothrissa.
Doubt has existed about the monophyly of the Paracanthopterygii ever since its erection by Greenwood et al. (1966) and subsequent redefinitions. Nelson (1994) followed the then most recent analysis of the group by Patterson and Rosen (1989), but it was also concluded by Nelson (1994) that "There is still no rigorous definition of the group; in other words, there is no firm basis to
Was this article helpful?