Genus Amphinema Haeckel, 1879 (Cnidaria, Hydrozoa): A brief taxonomic review with the description of a new species?

The genus Amphinema comprises a group of hydrozoans within the order Anthoathecata, currently consisting of 20 species, 19 of which have detailed morphological descriptions of their medusoid stage (Schuchert et al., 2025). The hydromedusae of this genus exhibit a combination of distinctive diagnostic features, including an apical projection, two hollow and opposite marginal tentacles, numerous rudimentary marginal warts or bulbs, a manubrium with four simple lips, absence of a gastric peduncle, and gonads located in adradial, interradial, or perradial positions, which occasionally extend along the radial canals (Bouillon, 1999; Bouillon et al., 2006; Fuentes et al., 2012; Schuchert & Collins, 2021). As part of a systematic review of the hydromedusae of Colombia, the morphological characteristics of 56 specimens collected from two coastal sites in the department of Córdoba (Colombia) were analyzed and compared with the diagnostic traits of the nominal species of the genus Amphinema. Based on these analyses, a synthesis of the diagnostic features of the reviewed species is presented, along with the morphological description of a potential new species to science. This taxon differs primarily in the shape and anatomy of the umbrella, apical projection, “gonads”, mouth, and lips. Given the high morphological plasticity observed within this group, it is proposed that molecular analyses be conducted to support the taxonomic identification. Documenting the diversity of hydromedusae contributes significantly to understanding the country’s marine biodiversity and provides a foundation for future studies on aspects such as ecology, phylogeny, and biogeography.