Gnosonesima laumeri sp. nov. http://zoobank.org/ urn:lsid:zoobank.org:act: E2B2068F-95B9-44D6-BB5F-21B28CEC5764 Ocean Census species No. 363 (Fig. 1) Diagnosis. Species of Gnosonesima unpigmented and without eyes. Male copulatory bulb including an 80-µm-long, straight stylet, ending in a sharp tip with an obliquely angled opening. Etymology. Species dedicated to Dr Christopher Laumer in recognition of his contribution to the study of gnosonesimids and his invaluable insights into the platyhelminth phylogeny. Material. One specimen studied alive and whole-mounted, designated holotype (USNM 1694165). Description. The specimen measured 433 µm long, with a pointed anterior and a broad posterior end (Fig. 1A). It was colourless and without eyes. The pharynx (Fig. 1A–B: ph) measured 217 µm in length and 96 µm at its widest posterior point. The internal pharynx (Fig. 1A–B: iph) was 63 µm long and 52 µm at its widest point. The genital organs were in the posterior half of the body. There were two testes (Figs. 1A, 1C: t) which connected to a seminal vesicle (Figs. 1A, 1C: sv). The seminal vesicle opened proximally into the male bulb, which includes proximally the prostate vesicle (Fig. 1C: pv) and carries a stylet (Figs. 1A, 1C: st; 1D–E). The stylet was 80 µm long, straight, tapering towards an oblique, sharp tip. The male accessory organ (Fig. 1: ao) was relatively long and presented a proximal, sac-shaped, glandular area, and a distal poorly developed stalk (maybe not fully developed or lined by weak muscles). The male gonopore (Fig. 1C: mg) opened at 60% and was surrounded by a glandular area (Fig. 1C: g). The female system was not developed. However, posterior to the male system the primordia of ovaries (Fig. 1C: pov) and a bursa (Fig. 1C: pb) were differentiated.

Published as part of Diez, Yander L., 2026, Three new species of Gnosonesima Reisinger, 1926 (Platyhelminthes: Gnosonesimida) from the subtropical Western Atlantic, pp. 105-112 in Zootaxa 5768 (1) on pages 106-107, DOI: 10.11646/zootaxa.5768.1.6, http://zenodo.org/record/19178066