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A new interstitial copepod, Meloriastacus ctenidis gen. et sp. nov. (Harpacticoida, Leptastacidae), is described from the shallow Meloria Shoals, Tuscany (Italy). It represents the most primitive leptastacid known to date, displaying several unique plesiomorphic character states previously unknown in the family. A sistergroup relationship with Archileptastacus Huys is suggested on the basis of the detailed structure of the caudal ramus, the fifth legs, the distal endopodal armature of P2‐P4 and the presence of spinule rows on either side of the anal opening. The ancestral leptastacid condition for the P5 setation is re‐assessed and the homology of the caudal ramus setae discussed. The structure of the mouthparts in Meloriastacus suggests that mucus‐trap feeding was adopted only secondarily in the evolution of the family.

Of the thaumastodermatid gastrotrichs that were collected in the years 1989–1991, during a faunistic survey of the Italian coasts, several have been placed in the genus Tetranchyroderma. On the basis of their distinctive morphological characters, four that bear pentancres are being described as new species, three with a complete dorsal covering of ancres: T. kontosomum, T. polyprobo‐lostomum, T. tanymesatherum, and one with an incomplete covering: T. anomalopsum.