Wollastonia falknerorum Groh, Neiber & De Mattia

Mattia, Willy De, Neiber, Marco T. & Groh, Klaus, 2018, Revision of the genus-group Hystricella R. T. Lowe, 1855 from Porto Santo (Madeira Archipelago), with descriptions of new recent and fossil taxa (Gastropoda, Helicoidea, Geomitridae), ZooKeys 732, pp. 1-125 : 37-39

† Wollastonia falknerorum Groh, Neiber & De Mattia sp. n. Figs 126-128, 129

Type material.

All from Porto Santo, holotype, SMF 348925, from loc. typ., leg. W. De Mattia & J. Macor, May 24 2015; SMF 348926/2 PT, NMW.Z.2016.013.00007/2 PT, NHMW 112142/1 PT, CKG/2 PT, CWDM/22 PT, from loc. typ., leg. W. De Mattia & J. Macor, May 24 2015; NMG No. 78-14764/2 PT [as H. vermetiformis , det. H. Waldén], Prainha & Serra de Fora, 33°03'57"N / 16°17'49"W, 20 m, leg. A. De Noronha, before 1978; NMG No. 86-17153/4 PT [as H. vermetiformis , det. H. Waldén], Penedo, 33°03'38"N / 16°19'50"W, 10 m, leg. J. J. De Sousa, before 1986; CWDM/9 PT, Barbinha, slightly S towards the tunnel, Quaternary mixed gravel slope deposit, 33°3'56"N / 16°17'49"W, 20 m, leg. W. De Mattia & J. Macor, May 24 2015; CKG/9 PT, Vale do Touro, 800 m E of Vila Baleira, 60 m NW of oil tanks, Quaternary slope deposit from the 3rd of 11 layers of tuffites with approx. 20% of stones, 33°03'49"N / 16°19'21"W, 12-14 m, Jun. 18 1983, leg. K. & C. Groh; CJG/3 PT, Vale do Touro, 800 m E of Vila Baleira, 60 m NW of oiltanks, Quaternary slope deposit from the 3rd of 11 layers of tuffites with approx. 20% of stones, 33°03'50"N / 16°19'21"W, 12-14 m, leg. J. Gerber, K. Groh & J. Hemmen, Aug. 16 1985; CKG/3 PT + 2 juv. (no PT), Pico dos Maçarico, opposite to Porto de Abrigo, leg. K.-H. Beckmann, Jan. 17 1998; CFW 12179/1 PT, Ponta da Galé, W end of tunnel, 300 m towards port, 33°03'36"N / 16°17'58"W, 25 m, leg. F. Walther, Apr. 1 2017; CFW 12178/10 PT + 4 juv. (no PT) + fragm. (no PT), Ponta da Galé, W end of tunnel, 100 m towards port, 33°03'38"N / 16°17'51"W, 35 m, leg. F. Walther & E. M. Gryl, Apr. 1 2017; CFW 12177/13 PT + 6 juv. (no PT) + 1 fragm. (no PT), CKG/3 PT, Ponta da Galé, E end of tunnel, lower level [of slope deposits], coarse, red coloured gravel with large stones, 33°03'47"N / 16°17'45"W, 30 m, leg. F. Walther, Apr. 1 2017; CFW 12180/34 PT + 11 juv. (no PT) + fragms (no PT), CKG/5 PT, E of Vila Baleira, end of Vale do Touro, (sub-)fossil [slope-]deposits, coarse, black gravel, 33°03'48"N / 16°19'15"W, 20 m, leg. F. Walther, Apr. 5 2017; CFW 12181/21 PT + 4 juv. (no PT) + fragms (no PT), E of Vila Baleira, S-slope of the hill above Vale do Touro, W of the oil tanks, [(sub-)fossil slope-deposits of] red gravel, 33°03'47"N / 16°19'26"W, 25 m, leg. F. Walther, Apr. 5 2017; ANSP H 11854/9 PT [partim, together with 7 H. subcarinulata and 2 Discula cheiranticola ], Barbinha, 33°04'04"N / 16°17'49"W, 8 m, leg. J. & C. Hemmen & K. & C. Groh, 1983.

Locus typicus.

Porto Santo, Pico do Baixo, E entrance of the tunnel, Quaternary mud deposit, 33°3'44"N/16°17'45"W, 20 m.

Diagnosis.

Wollastonia species with two keels on the body whorl, the upper keel only very weakly developed; suture overlapping; granulation very fine; ribbing of the body whorl rather coarse.

Description of the holotype.

Shell large for the genus, with 6.5 regularly increasing whorls, the protoconch with 2.1 whorls. The form of the shell is conical, the convex teleoconch whorls show an upper, rounded angulation and a lower distinctly developed keel. The last whorl measures 60%, the penultimate whorl 10%, of the total shell height. The lower ¾ of the body whorl are beneath the keel, which is set off by a constriction above and below; shell below the lower constriction regularly convex in frontal view. The angulation of the body whorl is placed in the upper seventh of its total height and the keel in the upper fourth of its total height. The suture between the whorls is simple, but slightly overlapping the previous whorl. The aperture, which is inclined to the vertical axis of the shell in an angle of 54° and is descending in the last 5% of the last whorl in an angle of 42° to the horizontal axis, has an elliptic form, which is slightly narrowed towards the columella. Its width is 45%, of the total shell width and its height 31% of the total shell height. It has a slightly reflected lip, which is completely detached from the body whorl. The eccentric umbilicus, which measures 14% of the shell's total width, is in the last whorls circular and completely closed in earlier whorls. The protoconch is smooth, the teleoconch shows a number of oblique radial ribs, 9 in the penultimate quadrant of the body whorl and is additionally covered by numerous small, rounded tubercles. The number of tubercles in the standard-quadrate of the base is 135. There are traces of colouration in form of large blotches along the last two whorls (see Fig. 126).

Variation of the paratypes.

The shell shape is quite stable in all examined specimens (Figs 127-128).

Measurements.

D 8.4 ± 0.1 mm (range 8.2-8.5 mm); H 7.0 ± 0.3 mm (range 6.8-7.4 mm); FW 4.3 ± 0.2 mm; PA 42 ± 5.3°; DU 0.9 ± 0.09 mm; NT 68 ± 18; NW 6.5 ± 0.2 (n = 20). Ratio D/H 1.2; ratio FW/H 0.6.

Distribution.

Wollastonia falknerorum sp. n. is found in the Quaternary mud and slope deposits along the southeastern coast of Porto Santo. Its range extends from the hills east of Vila Baleira to Barbinha, S of Porto dos Frades. The distribution is shown in Fig. 129.

Etymology.

Named for the German malacologists Margrit & Gerhard Falkner, Hörlkofen, to honour their highly valuable contributions to European malacology.

Comparison and comments.

Wollastonia falknerorum sp. n. can be confused on first glance with other comparatively large-sized geomitrid species like, H. echinoderma , W. ripkeni sp. n. and W. vermetiformis . From the first it is distinguishable by the presence of two distinct keels and from all three by a much finer sculpture. From the most similar W. vermetiformis and W. ripkeni sp. n. it is differentiated by the weakly developed upper keel, an overlapping suture, a much finer granulation and coarser ribbing of the body whorl. From similar-sized W. subcarinulata and W. inexpectata sp. n. it is separated by the two keels and the differently developed suture.

Taxonomic remarks.

Wollastonia falknerorum sp. n., as with other subfossil Wollastonia species, is included in this genus because it is similar to W. oxytropis in shell shape, size and surface sculpture, which differ considerably from Hystricella species. We are well-aware that, due to the lack of anatomical and molecular data, the generic position of this subfossil species is exclusively based upon shell features, with all the taxonomic limits that this might implicate.

Status and conservation.

Extinct before the islands’ scientific exploration in the 19th century, possibly already before human settlement.