Shell elongate fusiform, sometimes widely fusiform or turriform, typically with high spire and long to very long siphonal canal. Suture typically canaliculated or impressed, often resulting in telescopic appearance of spire. Whorls outline varying from subcylindric to flattened or evenly convex. Axial sculpture of straight ribs strong and widely set to fine and closely set. Spiral sculpture varying from fine grooves, restricted to siphonal canal or pronounced in interspaces between axials only, to strong cords overriding axial ribs to form beads or strong gemmae at intersections. Aperture elongate, its outer lip smooth or bearing fine lirae on its inner surface. Inner lip with between three and five columellar folds, with the upmost fold being the strongest. Shell coloration light, off-white, whitish, or pale, often with darker spiral bands. Head-foot pale, eye tentacles long, with eyes situated laterally at their bases. Radula rachiglossate, with tricuspidate rachidian of varying morphology and unicuspidate widely sickle-shaped or triangular laterals. Jaw present in some species, situated in buccal mass, thin, horseshoe-shaped. Gland of Leiblein glandular, very large, brown. Males with open seminal groove.

Distribution and habitat
Broadly distributed in the Indo-Pacific, from Madagascar to Japan and French Polynesia (300-1000 m), and in the Caribbean, lower subtidal and bathyal depths, on soft bottoms.


Remarks
Our molecular data (both phylogenomics, and DNA barcoding), revealed a close affinity of the
Caribbean species Turricostellaria lindae with Indo-Pacific Tosapusia. The radula of T lindae,
studied here for the first time, matches the circumscription of Tosapusia (Fedosov et al.
2017). Based on this result, we consider Turricostellaria as a synonym of Tosapusia; the latter genus therefore has a circumtropical distribution. Whether other species currently classified in Turricostellaria belong to this same radiation remains to be confirmed. Having examined the types of Turricostellaria amphissa Simone & C. Cunha, 2012. T apyrahi Simone & C. Cunha, 2012, T.jukyry Simone & C. Cunha, 2012, T. leonardhilli Petuch, 1987, and T. ovir Simone & C. Cunha, 2012, we conclude that the only species that certainly is not related to this group of costellariids is T amphissa.
The adapical columellar fold in this species is weaker than the following one, this configuration suggests volutomitrid affinities of the species. Here we tentatively reassign this species to Microvoluta based on its conchological resemblance with the type species Microvoluta australis Angas, 1877.
Because this transfer results in a secondary homonymy with the Indo Pacific Microvoluta amphissa Bouchet & Kantor 2004, we here propose a replacement name Microvoluta abrolhosensis nom. nov. for the Brazilian species. The remaining four species formerly placed in Turricostellaria are here reassigned to Tosapusia.
We identified 11 SSHs within Tosapusia, of which there are names available for at least 8 However, the analysis of the DNA barcoding data demonstrated notable inconsistency between the (mitochondrial) phylogeny, and morphology. We show that closely related lineages / populations may drastically differ in shell morphology (e.g. PSH 59), and on the contrary similar morphotypes (e.g. those referred to as 'evelyniana' or 'duplex') may emerge (or be retained) in very distantly related lineages. So, even though we have identified four SSHs for which a total of two names only are available, we are uncertain as to which SSHs the names Tosapusia evelyniana and T duplex should be applied to. Furthermore, as two (SSH 60 and SSH 203) are represented by singletons, with only mitochondrial DNA data available, we do not further treat these here pending more data. The formal description is therefore provided only for SHH 144, represented by five specimens from New Caledonia and the South China Sea.

Members of Tosapusia display high disparity in all key elements of shell morphology - shell shape and proportions, whorl profile, sculpture pattern, and shape of the suture - making it quite difficult to determine shared characters in order to establish the identity of the genus. Conchologically, different Tosapusia species may resemble members of other costellariid genera rather than congeners. Tosapusia isaoi and Tosapusia sauternesensis, with their high spire and relatively short siphonal canal, resemble some deepwater species of Vexillum, like Vexillum tokubeii (Sakurai & Habe, 1964) or Vexillum scitulum (A. Adams, 1853), but can be distinguished by the shape of the axial ribs, which are always straight in Tosapusia, but are arcuate and usually slightly undulating in Vexillum. The tip of the siphonal canal is distinctly notched in Vexillum, whereas Tosapusia species have a relatively longer siphonal canal, never notched at its tip, which easily distinguishes the two genera.

Distribution and habitat
Indo-Pacific, from Madagascar to Japan and French Polynesia, in deep water (300-1000 m) on soft bottoms.