Itaipusa aberrans Diez, Aguirre, Reygel & Artois sp. n. (Fig. 2) urn:lsid:zoobank.org:act: 171C2F91-B386-4BD4-B07A-CCDC27FAD1F1 Material and distribution. One specimen studied alive and whole mounted, designated holotype (FMNH https:// id.luomus.fi/ KV.646), collected in Siboney (19°57’34”N; 75°42’07”W) (Type Locality), Santiago de Cuba, Cuba (April 5, 2017), fine-grained sand rich in organic matter, 0.3 m deep, salinity 34 ‰. Etymology. Species named after the unique and aberrant structure of the cirrus. Diagnosis. Species of Itaipusa with an armed cirrus subdivided into two short, heavily folded plates, connected to each other by a thin duct lined by some small teeth. One plate is 32 μm long and bears a few spines 3–4 μm long. The second plate is spiral-shaped and armed with a few 1–9 μm long spines. Description. The specimen is 1.7 mm long, unpigmented, with two eyes (Fig. 2A: e). Proboscis (Fig. 2A: pr) of the typical koinocystidid construction (see Brunet 1972; Karling 1980); it is 10% of the body length in the live animal. The pharynx (Fig. 2A: ph) has a diameter of 15% of the body length in the live specimen, situated at 50%. A pair of testes is located antero-laterally from the pharynx. Paired elongated seminal vesicles fuse to form a short seminal duct just before entering into the copulatory bulb. The ovoid copulatory bulb (Fig. 2A: cb) encloses the prostate vesicle (typically encompassing numerous filiform ducts) and the armed cirrus (Fig. 2B–E). The cirrus is subdivided into two short, armed plates connected to each other by a narrow structure with some small folded sclerotised pieces (Fig. 2E: sfp). The first plate (Fig. 2B, 2D–E: pl1) is a heavily folded spiral and bears few 4–9- μm-long spines (x̄ = 7 μm; n = 5). The second plate (Fig. 2C, D–E: pl2) is 32 μm long, and also shows numerous folds and bears a few spines of 4–5 μm long (x̄ = 4 μm; n = 4). The spines of the structure connecting both plates are 1–2 μm long (x̄ = 1 μm; n = 8). The two elongated ovaries lie at midbody. The oocytes are organised in a row, increasing in diameter from the most proximal to the most distal one. The ovaries are flanked by the vitellaria (Fig. 2A: vi), which extend from behind the eyes to the caudal body end. The female duct receives the oviducts and opens into the female atrium through a strong sphincter. The caudally-located bursa is weakly muscular and contains sperm. The bursal stalk is very muscular and connects the bursa with the female atrium.

Published as part of Diez, Yander L., Monnens, Marlies, Aguirre, Rosa Isabel, Yurduseven, Rana, Jouk, Philippe, Van Steenkiste, Niels W. L., Leander, Brian S., Schockaert, Ernest, Reygel, Patrick, Smeets, Karen & Artois, Tom, 2021, Taxonomy and phylogeny of Koinocystididae (Platyhelminthes, Kalyptorhynchia) with the description of three new genera and twelve new species, pp. 451-500 in Zootaxa 4948 (4) on pages 459-460, DOI: 10.11646/zootaxa.4948.4.1, http://zenodo.org/record/4629235