Revision of Trigonostomum Schmidt, 1852 (Platyhelminthes, Typhloplanoida, Trigonostomidae) with the description of seven new species Author Willems, Wim R. Author Artois, Tom J. Author Vermin, Wouter A. Author Schockaert, Ernest R. text Zoological Journal of the Linnean Society 2004 2004-06-30 141 2 271 296 https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2004.00124.x journal article 5407 10.1111/j.1096-3642.2004.00124.x d15c737e-c0cb-4f09-98dd-d707de72a43a 0024-4082 4634553 TRIGONOSTOMUM MESSOPLANOIDES ARTOIS ET AL., 2000 ( FIG. 6B ) Alternative species name: trigonostomummessoplanoides Trigonostomum messoplanoides Artois et al. , 2000: 104–105 , fig. 1. Known distribution: Weddell Sea, Antarctica ( Artois et al. , 2000 ). Material examined: Holotype ( LUC , no. 207). Diagnosis: Trigonostomum species with stylet 225 Mm long, proximally bent over 270∞. Mantle with stylet 75 Mm long, flagelliform spine surrounding only the distal part of the stylet. Bursal appendage 22 Mm long, with a proximal ring and two distal tubes. Remarks: The copulatory organ of T. messoplanoides resembles that of some species of Messoplana ( Artois et al. , 2000 ) , for instance M. elegans ( Luther, 1948 ) Den Hartog, 1966 , M. helgolandica Ax, 1971 , M. pacifica Karling, 1986 and M. rugata Ehlers, 1974 . However, the presence of a ventral invagination clearly confirms that it is a species of Trigonostomum .