Marinellia lingulifera Riedl 1954

MARINELLIA LINGULIFERA RIEDL, 1954

Marinellia lingulifera Riedl, 1954: 223–231, figs 30– 32.

Distribution: Mediterranean Sea (Riedl, 1954).

This species was considered by Riedl (1954) to be a close relative of Trigonostomum, mainly based on the presence of an antero-ventral invagination forming a kind of ‘proboscis’. Other features in which M. lingulifera resembles Trigonostomum species are the pharynx, which is strongly inclined forwards and shows very strong external muscles and weak radial ones (Riedl, 1954: 227), the double connection in the female system (Riedl, 1954: fig. 31), the presence of a bursa (Riedl, 1954: fig. 31: rs) with a long and narrow bursal stalk, paired ovovitellaria and a bursal appendage that consists of two coiled tubes, fused at their base (Riedl, 1954: 225). Three other features of M. lingulifera are not found in any Trigonostomum species: the presence of a muscular tongue in front of the pharynx (Riedl, 1954: 227–228, fig. 31: z), a muscular septum connecting the invagination with the pharynx (Riedl, 1954: fig. 31: ms), and an unpaired seminal vesicle (Riedl, 1954: 226). Ax (1971) considered M. lingulifera to be the sister group of Trigonostomum, based only on the presence of the antero-ventral invagination. There is, however, no material of this species available and some of the observations, such as the unpaired seminal vesicle, the detailed structure of the copulatory organ and the invagination certainly need confirmation. In addition, the copulatory organ and the bursal appendage are insufficiently described and not even figured in the original description.