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The genus Sphenothallus was erected by Hall (1847, p. 261), who originally considered it a land plant. Sphenothallus was later classified as a marine invertebrate. Moore and Harrington (1956, p. F65) regarded Sphenothallus as a hydrozoan or scyphozoan. Van Iten et al. (1992, p. 139) supported Moore and Harrington's idea, and argued that it displays a close relationship to conularids (also see Li, 2000, p. 91). However, Mason and Yochelson (1985, p. 93–94) suggested that Sphenothallus is an annelid or “worm” (also see Fauchald et al., 1986, p. 64; Feldmann et al., 1986, p. 344–345; Choi, 1990, p. 403; Bartels et al., 1998, p. 114–117). The exact phylogenetic affinity of Sphenothallus is still debated. Sphenothallus has been recognized in Paleozoic rocks ranging from Cambrian to Permian, at numerous localities in the northern and southern hemispheres (Van Iten et al., 1992, p. 136; Neal and Hannibal, 2000, p. 369; Li, 2000, p. 88, 89; Baird and Brett, 2002, p. 208). Up until now, few reports of sphenothallids have been published from the Silurian. Murchison (1839) reported two sphenothallids from the Silurian of Scotland. Billings (1862) described one sphenothallid: Serpulites dissolutus Billings (pl. 1.1, figs. 6, 7) from the Lower Silurian; however, Bolton (1994, p. 4) considered the geological age of specimens, classified as Sphenothallus angustifolius , to be Middle Ordovician. Brood (1988, p. 83) published sphenothallid phosphatic tubes from the Ludlow rocks of Gotland under the generic name Campylites . In China, Sphenothallus has been solely reported from the Cambrian only at two localities: Taijiang, Guizhou (Zhu et al., 2000, p. 229–234) and Nanzheng, Shaanxi (Li, 2000, p. 93). The purpose of the present paper is to describe Sphenothallus angustifolius Hall based on …