Species of Novibipalium are very similar to those of the related genus Bipalium. The main difference occurs in the copulatory apparatus, which in Novibipalium lacks a well-developed penis papilla, while in Bipalium a penis papilla is present. Novibipalium has a set of folds in the copulatory apparatus that are everted during mating and create a temporary penis.[1]
^ abKawakatsu, M.; Sluys, R.; Ogren, R. E. (2005). "Seven new species of land planarian from Japan and China (Platyhelminthes, Tricladida, Bipaliidae), with a morphological review of all Japanese bipaliids and a biogeographic overview of Far Eastern species". Belgian Journal of Zoology. 135 (1): 53–77.
^ abSolà, E., Sluys, R., Riutort, M., Kawakatsu, M. (18 August 2023). "Molecular phylogenetics facilitates the first historical biogeographic analysis of the hammerhead worms (Platyhelminthes: Tricladida: Bipaliinae), with the description of twelve new species and two new genera". Zootaxa. 5335 (1): 1–77. doi:10.11646/zootaxa.5335.1.1. ISSN1175-5334.