Lanternfishes (Myctophidae) with otoliths in situ from the Early Oligocene of the Eastern Paratethys (western Ukraine)
Abstrakt
Articulated myctophid fish skeletons are described from the Early Oligocene of western Ukraine. They consist of two species, Oligophus moravicus and an unspecified representative of the genus Eomyctophum; both taxa have been previously reported from coeval strata of the Paratethys.
All the six specimens (two are plate and counterplate) contain otoliths in situ. Those of Oligophus moravicus are well-preserved and lead to synonymization of the otolith-based Diaphus longirostris.
Those of Eomyctophum sp. are less well-preserved, but may represent one of two closely related otolith-based species, namely Diaphus alcoholicus and Diaphus pristismetallis. It is thus shown that the record of skeleton-based and otolith-based taxa from the Early Oligocene of the Paratethys indeed corresponds well.
However, the skeleton-based data suggest a predominance of stem-group myctophids, while the otolith-based data were interpreted to only represent the extant genus Diaphus. The phylogenetical position of Oligophus moravicus, until recently assigned to the genus Diaphus, is briefly discussed.
It is concluded that unambiguous records of fossil Diaphus species are recognized only from the Late Oligocene onwards.