SYSTEMATICS OF THE DEROPRISTIIDAE CABLE AND HUNNINEN, 1942 (TREMATODA) AND BIOGEOGRAPHICAL ASSOCIATIONS WITH STURGEONS (OSTEICHTHYES, ACIPENSERIDAE)

The 11 nominal species of the Deropristiidae, belonging to the genera Deropristis (three species), Pristicola (one species), Skrjabinopsolus (five species) and Cestrahelmins (two species) were re-evaluated for a phylogenetic and biogeographical analysis of the group. Skrjabinopso lus elongatus (Madhavi, 1974) (= S. indicus Gupta & Ahmad, 1976, S. ku rotchkini Parukhin, 1976), S. sanyaensis Shen, 1990, Deropristis pauro soma Wang, 1989 and Cestrahelmins Fischthal, 1957, do not belong to th e Deropristiidae. The genus Opisthodiplomonorchis Madhavi, 1974 is res urrected for its type-species, O. elongatus (= S. elongatus), and D. p aurosoma is also transferred to this genus. Species of Opisthodiplomon orchis occur in polynemid fishes of the Indo-Pacific. Five nominal spe cies thus comprise the Deropristiidae, i.e. S. armatus Ivanov in Ivano v and Mrygin, 1937, S. manteri (Cable, 1952), D. hispida (Abildgaard, 1819), D. inflata (Molin, 1859) and P, sturionis (Little, 1930), which corresponds to the original composition of the family. A comparison o f Skrjabinopsolus from acipenserids in North America and Europe reveal ed variability in morphological characters considered diagnostic in th e past (body size and position of the ovary and testes). Based on the morphology and biology, the two species of Skrjabinopsolus can be cons idered incipient species. A phylogenetic analysis of the redefined Der opristiidae indicates that Deropristis and Pristicola may form a monop hyletic group with Skrjabinopsolus as the sister taxon. The biogeograp hy of the Deropristiidae suggests an origin and distribution associate d with the formation of the North Atlantic basin. Freshwater and marin e/estuarine origins for the family are equally parsimonious possibilit ies. A freshwater origin can be traced at least to Cretaceous Laurasia followed by a drift-vicariance separation and subsequent association with North Atlantic drainages. Support for a marine ancestry of the De ropristiidae is indicated by the biogeography of its sister taxa (outg roups in this study) and of its hosts, and is also consistent with an Atlantic origin. The deropristiids evidently originated and speciated within the Acipenseridae in the Atlantic region, with a host switch in to Atlantic Anguilla spp.