Prosthiostomum huidongense sp. nov., MBM287880 (holotype), schematic diagram (A) and photomicrographs of sagittal sections (B–E), anterior to the left. A. Copulatory complex and sucker; B. Anterior end of the body; C. Penis stylet; D. Male copulatory apparatus; E. Copulatory complex and sucker. Abbreviations: ab – anterior branch of main intestine; br – brain; cg – cement glands; cp – cement pouch; fg – female gonopore; it – intestine; m – mouths; ma – male atrium; mg – male gonopore; ph – pharynx; pv – prostatic vesicle; spv – spermiducal vesicle; st – stylet; su – sucker; sv – seminal vesicle; va – vagina; ut – uterus. Scale bars: 0.5 mm (A, E); 200 μm (B); 50 μm (C, D).