Siphonalia pfefferi G. B. Sowerby III, 1900

Kantor, Yuri, Kosyan, Alisa & Sorokin, Pavel, 2020, On the taxonomic position of Phaenomenella Fraussen & Hadorn, 2006 (Neogastropoda, Buccinoidea) with description of two new species, Zoosystema 42 (3), pp. 33-55 : 52

Siphonalia pfefferi G. B. Sowerby III, 1900

( Figs 9D, E ; 11C, D ; 12 )

Siphonalia pfefferi G. B. Sowerby III, 1900: 440 , pl. 11, fig. 3.

MATERIAL EXAMINED. — Japan • 1 lot, 2 specimens; Off Hashima, Miyazaki Prefecture, Kyushu; 10.V.1996 (nos. 1, 2, figs 8D, E).

COMPLEMENT TO DESCRIPTION

Radula

Radula rather similar in both specimens ( Fig. 11C, D ); central tooth with rectangular basal part and weakly arcuate anterior margin and three medium long triangular broad cusps, central one equal in length but slightly narrower than lateral ones. Lateral teeth tricuspate with weakly curved basal side, attached to membrane. Outermost cusp recurved, medium long, inner cusp weakly recurved, about 2/3 of outer cusp length; inner cusp in right longitudinal row of specimen spm. no. 2 partially subdivided ( Fig. 11D ). Intermediate cusp shortest, situated closer to inner cusp; inner cusp of spm. no. 2 partially subdivided in left longitudinal row.

Anatomy (spm. no. 1, male, Fig. 12 )

Head very short and broad, tentacles short, contracted, with small eyes at lobes. Foot contracted, propodium moderately wide, operculum oval with terminal nucleus. Penis rather large ( Fig. 12C ), flattened, with long narrow seminal papilla in deepening at the top. Mantle with medium long siphon.

Digestive system. Proboscis partly everted out of rhynchodaeum, with contracted walls. Multiple proboscis retractors attaching mostly along right side of anterior oesophagus ( Fig. 12D, E , prr), connecting rhynchodaeum and lateral walls of body haemocoel. Buccal mass slightly shorter than retracted proboscis ( Fig. 12F , bm), attaching to its walls by multiple odontophoral retractors (odr). Radula lying in middle of buccal mass and attached to proboscis walls by median retractor ( Fig. 12F , mrr). Salivary glands ( Fig. 12D, E , sg) medium large (0.4 proboscis length), oval, with salivary ducts following on both sides of anterior oesophagus. Anterior oesophagus wide, dorso-ventrally flattened ( Fig. 12E , aoe), valve of Leiblein rounded, medium large. Posterior oesophagus (poe) relatively narrow. Gland of Leiblein large, folded beneath nerve ring ( Fig. 12E , gl). Stomach spanning about 0.3 whorl ( Fig. 12G ). Posterior mixing area not large ( Fig. 12G, H , pma). Intestine medium wide. Opening of posterior duct of digestive gland located near oesophageal opening ( Fig. 12I , pdg), opening of anterior duct located closer to beginning of intestine. Inner stomach wall between two openings contains longitudinal fold ( Fig. 12H , lfl), lined with low oblique folds, rest part of inner and outer stomach wall lined with moderately high transverse folds.

Results of the phylogenetic analysis suggest close affinities of Siphonalia and Phaenomenella that remained unnoticed previously. Fraussen & Hadorn (2006), while describing Phaenomenella , compared it to Manaria and Eosipho , but not to Siphonalia . The shell outline of some Phaenomenella (e.g. Phaenomenella insulapratasensis ) is rather similar to Siphonalia : the shell is stout, with strongly convex whorls and a recurved siphonal canal. Species of Phaenomenella though have a much larger (about twice) protoconch in comparison with Siphonalia . The intrageneric variability of shell shape in Phaenomenella in its current definition is very high ( Fraussen & Stahlschmidt 2013) and in its extremes there is no resemblance between the two genera. It should also be born in mind that some of the most diverging species of Phaenomenella were not yet sequenced and may fall into other lineages.

Representatives of both genera are also anatomically similar, particularly in the digestive system characters. Both Phaenomenella and Siphonalia have a broad, medium long in the contracted state proboscis, medium large salivary glands and a large gland of Leiblein. It should be mentioned that despite these general similarities, there are no unique morphological characters uniting both genera. The radular morphology is very similar in both genera ( radula of one more species, S. marybethi Parth, 1996 was illustrated in Zhang & Zhang 2018), however, as in the case with the body anatomy, it is of rather generalized buccinid appearance; similar radular morphology can be found in many unrelated genera – eg. Latisipho Dall, 1916 ( Kosyan 2006) , Plicifusus Dall, 1902 ( Kosyan & Kantor 2012), Aulacofusus Dall, 1918 ( Kosyan & Kantor 2013).

Our molecular analysis did not recover Phaenomenella as monophyletic. In both COI and combined COI+28S analyses the internal relationships within Phaenomenella – Siphonalia clade are not resolved. Siphonalia spadicea cluster without significant support with P. samadiae n. sp. We have only a single species of Siphonalia in our analyses so it is too preliminary to change the classification on the basis of the incomplete dataset. Therefore we presently retain the validity of Phaenomenella , although it is possible that Phaenomenella and Siphonalia can belong to a single genus. One of the distinctions between the genera is the depth range of known species. Generally, species of Siphonalia dwell at shallower depths – from 10 to 300 m ( Okutani 2000), while Phaenomenella is recorded at 190-1389 m ( Fraussen & Stahlschmidt 2013; herein). The new species are attributed to Phaenomenella based on stronger conchological similarity to other species of the genus rather than to species of Siphonalia . Unfortunately the protoconch of P. samadiae n. sp. was decollated in all available specimens, but the protoconch of P. nicoi n. sp. is large globose, similar to other species of Phaenomenella .

The analysis of a broader dataset of Buccinoidea rejected the monophyly of Siphonaliinae in its original scope. None of the Recent genera, originally included by Finlay (1928) in the subfamily, that are Penion, Aeneator and Glaphyrina , are closely related neither to each other, nor to Siphonalia . The system of Buccinidae and Buccinoidea in general is still far from being resolved, with many problematic buccinoidean lineages (see e.g. Couto et al. 2016; Harasewych 2018). Therefore the rank of the inferred clade Siphonalia + Phaenomenella can be resolved only after obtaining the robust phylogeny of the entire superfamily Buccinoidea.

Figures

FIG. 9. — Shells of studied Siphonalia spp.: A-C, S. cassidariaeformis (Reeve, 1846): specimen no. 1 (A), specimen no. 2 (B), specimen no. 3 (C); D, E, S. pfefferi G. B. Sowerby III, 1900; D, specimen no. 1; E, specimen no. 2. Scale bar: 10 mm.

FIG. 11. — Radulae of Siphonalia spp. A, S. cassidariaeformis (Reeve, 1846) no. 1; B, S. cassidariaeformis no. 2; C, S. pfefferi G. B. Sowerby III, 1900 no. 1;

FIG. 12. — Anatomy of Siphonalia pfefferi G.B. Sowerby III,1900, specimen no.1: A, cephalopodium,ventral view;B, cephalopodium,dorsal view,mantle removed; C, penis; D, foregut, dorsal view; E, foregut, ventral view; F, proboscis opened dorsally; G, stomach, external view; H, stomach, opened dorsally. Abbreviations: see material and methods. Scale bars: A-F, 10 mm; G, H, 5 mm.