Two series of parapophyses in neoscopelid fishes (teleostei: Myctophiformes)

Abstract

Observations of the vertebrae of three genera and five species of neoscopelid fishes revealed the presence of two series of parapophyses (a ventral series and a lateral foveal series). The ventral parapophyses, situated on the ventral surface of the centra, were present on only the anterior abdominal vertebrae (AV): inScopelengys (AV1, 2),Neoscopelus (AV1–6 or 7),Solivomer (AV1–8). Parapophyses on the first vertebra were ossified, cone-shaped enlargements, the remainder being small, cartilaginous and ovalshaped. The lateral foveal parapophyses were formed from an extension of the lower edges of the foveae on the lateral surfaces of the centra, into which the ribs are set, being developed caudally to form the hemal arches: inScopelengys (AV4 posteriorly),Neoscopelus (AV6 or 7 posteriorly),Solivomer (AV8 posteriorly). The last ventral cartilaginous parapophyses and first lateral foveal parapophyses were present on the same centrum in two genera,Neoscopelus (AV6 or 7) andSolivomer (AV8). Lateral foveal parapophyses series were also found in some acanthomorphs and a ventral parapophyses series in some non-acanthomorphs. Whereas the ventral papapophyses in the non-acanthomorphs developed posteriorly to form the hemal arches, this parapophyses series in neoscopelids is incomplete, being absent on the posterior abdominal vertebrae. This suggests that the ventral parapophyses series in neoscopelids seems to be a remnant of that in the non-acanthomorphs. In myctophids, although cartilaginous ventral parapophyses were absent posteriorly from the second vertebra, enlarged ossified cone-shaped parapophyses on the first vertebra (as in neoscopelids) and lateral foveal parapophyses usually from the third vertebra were present. Accordingly, myctophids appear to be similar to neoscopelids in having two types of parapophyses.