A redescription and relationships of the congrid eel Pavelichthys daniltshenkoi (Anguilliformes: Congridae) from the lower Oligocene of Northern Caucasus

This study reanalyzed the morphology and discussed the relationships of a unique fossil conger Pavelichthys daniltshenkoi from the lower Oligocene of the Northern Caucasus. It belongs to the family Congridae by the presence of fused frontalia and the hyomandibulare inclined forward but differs from all representatives of the family by a significantly protruding lower jaw in combination with a large horizontal mouth. Pavelichthys is characterized by nonsegmented rays of the dorsal and anal fins, deep non-tapering caudal part of the body, well-developed pectoral and caudal fins, presence of the lateral ethmoidal process, supraoccipitale, and leaflike broadened parapophyses on the middle and posterior body vertebrae, about 90 trunk vertebrae, vertebral formula 9–～60–～150. By the combination of the traits, the Oligocene form should belong to the subfamily Bathymyrinae.