Cancilla, SWAINSON, 1840

Fedosov, Alexander, Puillandre, Nicolas, Herrmann, Manfred, Kantor, Yuri, Oliverio, Marco, Dgebuadze, Polina, Modica, Maria Vittoria & Bouchet, Philippe, 2018, The collapse of Mitra: molecular systematics and morphology of the Mitridae (Gastropoda: Neogastropoda), Zoological Journal of the Linnean Society 183, pp. 253-337 : 306-308

GENUS CANCILLA SWAINSON, 1840

( FIGS 25I–M, 26)

Type species: Mitra isabella Swainson, 1831 ; SD, Herrmannsen (1846: 166).

Diagnosis: Shell small to rather large (15–110 mm), fusiform, with high aperture and long, tapering siphonal canal. Protoconch conical, of about three very slightly convex smooth whorls. Spire whorls evenly convex to subcylindrical; suture distinct, impressed. Shell sculptured with spiral cords that are slightly gemmate or with finely dentate margins, very wide and flat, separated by narrow grooves, or with strong, narrow and elevated cords separated by broad depressions bearing regular, very fine riblets. Shell base gradually extended into rather long, tapering siphonal canal. Siphonal fasciole not pronounced, notch deep or shallow. Aperture elongate, narrow; outer aperture lip smooth, gently convex adapically, and flattened in its lower portion. Inner lip with four oblique columellar folds, adapicalmost strongest. Shell pale or cream, typically with multiple darker spiral strokes on crests of spiral cords. Radula with narrow rachidian, usually bearing four cusps, of which central pair notably stronger ( Fig. 25I–M). Lateral teeth with seven to ten pointed triangular cusps, second proximal cusp greatly exceeding others, and subsequently gradually weakening towards margins of radula.

Distribution: Indo-Pacific, bathyal depths, mostly on mud.

Species included: Cancilla baeri (Turner & Cernohorsky, 2003) 1, C. fibula Poppe, Tagaro & Salisbury , 20091, C. heinickei (Salisbury & Guillot de Suduiraut, 2003) 3 comb. nov., C. herrmanni Dekkers , 20143, C. isabella ( Swainson, 1831) 2, C. liliformis Huang & Salisbury 20173, C. rehderi (Webb, 1958) 1, C. rikae Guillot de Suduiraut , 20043, C. schepmani (Salisbury & Guillot de Suduiraut, 2003) 1 comb. nov., C. turneri Poppe, Tagaro & Salisbury , 20093.

Remarks: The typification of Cancilla renders the identity of the genus a little weak: the specimen of M. isabella originally illustrated by Swainson (1831) was selected as lectotype by Cernohorsky (1991), but, like many types of Swainson relevant to this study, this specimen is lost ( Cernohorsky, 1991). Taking in consideration frequent parallelisms in shell morphology demonstrated in Mitridae , the utility of Swainson’s original illustration for taxonomic decisions is limited and it will be desirable in the future to designate a neotype with associated molecular data.

The radula of C. isabella was studied by Salisbury & Huang (2015). Although the two specimens dissected by these authors differ notably in shell proportions, their radulae are morphologically close to each other, and rather peculiar. The rachidian bears two pairs of long pointed cusps (the lateral cusps being notably weaker than the central ones), flanked by two pairs of very weak cusps; the laterals bear long pointed cusps that progressively increase in size towards tooth mid-width, whereas the distal halves bear no cusps and show only weak serration ( Salisbury & Huang 2015: figs 1.1, 3.2), a pattern comparable to the laterals in Scabricola , which are however still more robust.

Of all Cancilla species studied by us, C. baeri is probably closest to C. isabella : the specimen of C. baeri MNHN IM-2013-58853 ( Fig. 26A) resembles one of the two specimens of C. isabella studied by Salisbury & Huang (2015: fig. 3.2b) in shell proportions, whorl outline and shape of the siphonal canal. The other studied Cancilla species – the C. rehderi – C. fibula complex and C. schepmani – are generally smaller, with less convex whorls and stouter siphonal canal, which is not clearly delineated from the shell base. Therefore, the genus Cancilla , as we circumscribe it, is rather heterogeneous and can be subdivided by shell morphology into two conventional groups: ‘robust’ Cancilla with species such as C. isabella , C. baeri and C. chuoi , and ‘slender’ Cancilla with species like C. fibula , C. rehderi , C. schepmani and C. liliformis . The relationships of these two conchological groups is supported by (1) inclusion of C. baeri in the Cancilla clade (clade 24–7) in the COI -based tree and (2) occurrences of very similar radular morphologies in ‘slender’ species of the C. fibula – C. rehderi complex ( Fig. 25I, K) and in ‘robust’ C. baeri IM-2013-58853 ( Fig. 25L). It should be noted, however, that the radula of C. schepmani ( Fig. 25M), with a morphology closest to the radulae of Strigatella or of the mitrine Neotiara nodulosa ( Fig. 10E), is thoroughly different from the radulae of other studied Cancilla species. Therefore, Cancilla appears to be very heterogeneous in radular morphology as well. Taking into account this observed radular disparity among sequenced (and thus confirmed related) Cancilla species, we believe that the divergent radular morphology of C. isabella does not contradict its affinity to the other species studied herein.

Species of Domiporta can be distinguished from the ‘robust’ Cancilla species by the sculpture pattern with narrow, elevated, widely interspaced spiral cords, whereas a distinct concavity at the transition of shell base to siphonal canal distinguishes species of Domiporta from ‘slender’ Cancilla species. Moreover, the two genera differ greatly in radular morphology. Besides, there is a clear resemblance between some species of Imbricaria and ‘slender’ Cancilla : I. fulgetrum and C. rehderi / fibula (especially our immature specimen IM-2013-19073) or the I. yagurai group and C. cf. fibula (represented by IM-2013-40646). In these pairs, the species of Cancilla can be recognized by the more convex outline of the shell base, which gives the shell a rather fusiform shape compared to the rather biconical shell of Imbricaria . The new genus Cancillopsis can be differentiated from the ‘robust’ Cancilla species by the higher spire with rather subcylindrical whorls, and from the ‘slender’ Cancilla species by the presence of a concavity at the base of the siphonal canal. Finally, the radula with rachidian and lateral teeth of similar morphology differentiates Profundimitra gen. nov. and Fusidomiporta gen. nov. from Cancilla .

GENUS IMBRICARIOPSIS FEDOSOV, HERRMANN ,