Diagnosis: Shell small to large (18—65 mm), fusiform with high spire and from very short to moderately long, slightly recurved, siphonal canal. Shoulder poorly pronounced, rarely weakly angulate. Protoconch multispiral, of up to more than four whorls; later whorls sculptured with closely spaced, axial, arcuate riblets. Subsutural cord from weak to moderately pronounced, occupying most of subsutural ramp with spiral ridges. Sinus cord on, or slightly above, periphery, strong, usually bipartite or further separated in three or four smaller cordlets. Shell base with distinct primary spiral cords and smaller cordlets between them; cords on canal much weaker, equal in size. Aperture oval, with short to moderately long siphonal canal (X. notata), slightly inclined abaxially. Anal sinus U-shaped, parallelsided, deep. Ground colour, cream-white to light-brown, spiral cords and cordlets with numerous, irregular brown spots and darker dots on cords. Sinus cord always with regularly spaced, dis¬tinct, darker brown spots of varying width. Radula : marginal teeth dúplex or semi-enrolled. In dúplex tooth, its anterior part (directed towards centre of radular membrane) solid for about 1/4-1/3 of the tooth length, pointed, usually with slightly recurved tip; in the posterior 3/4 to 2/3, major and accessory limbs broadly bifurcating, and accessory limb usually with clear constriction at fusión with major limb, of the same length, or slightly shorter than major limb. In semi-enrolled marginal teeth, both edges are elevated and equally developed along the entire tooth length, delimiting an intervening trough. The anterior solid part of the tooth is absent. Central formation of varying strength, usually weak and limited to central cusp, rarely with weak lateral extensions or completely reduced.
Remarks: In the RAD sequencing (Abdelkrim et al, 2018a) and exon-capture-based analyses, Xenuroturris legitima, which has dúplex marginal radular teeth, is sister to all other species. The genus Iotyrris was originally established for the species conchologically similar to Xenuroturris, but having semi-enrolled marginal radular teeth. Later more species with semi-enrolled teeth were discovered, and also included in Iotyrris based on this radular morphology (Kantor et al., 2008). However, some further species with dúplex marginal teeth (X. olangoensis, X. kingae and X. notata), once sequenced (Abdelkrim et al, 2018a), fell in the same clade as the species with semi-enrolled teeth, to which the ñame Iotyrris was applied; therefore, these two principal radular morphologies were no longer monophyletic. The recent exon capture analysis produced the same topology (Zaharias et al, 2024 ), and thus it can be confirmed that the type of marginal radular teeth is not consistent with the phylogeny and is not genus-specific. Therefore, we here synonymize Iotyrris with Xenuroturris.
Xenuroturris emmae is quite different from other species in the genus in that the orange-brown-coloured shell bears irregularly set lighter spots. In the absence of radular and molecular data, we only conditionally attribute the species to Xenuroturris.
Distribution: Entire Indo-Pacific from east Africa to Hawaii; mostly upper subtidal, rarely down to 180 m.
