Dadagulella radius Rowson & Tattersfield 2013, comb. et stat. nov.
Creators: name: Rowson, Ben
name: Tattersfield, Peter
Publisher: name: Zenodo
Year: 2013
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Stylommatophora
Streptaxidae
Dadagulella
Dadagulella radius

description: Dadagulella radius calva (Connolly, 1922) comb. et stat. nov.
Figs 6-8, 51, 84; Table 1
Gulella calva Connolly, 1922: 495, pl. XIV, fig. 35.
Gulella calva – Verdcourt 1962: 17; 1983: 234. — Richardson 1988: 62. — Verdcourt 2000: 215; 2006: 49.
? “ Gulella radius (Preston) var. (K, Mrima Hill Forest)” – Verdcourt 1962: 22.
Type material examined
KENYA: lectotype (here designated) NHMUK. 1937.12.30.486: 1 ad., Taru Desert (i.e. a semi-arid area of southeastern Kenya now partly in the Tsavo East National Park, approx. 3.40°S, 39.00°E), leg. Percival, labelled “type”, and apparently the shell figured in Connolly (1922: pl. XIV, fig. 35).
Other material examined
KENYA: NMW.1955.158.25052: 5 ads, “ca. lat. 3°5’, long. 39°27’”, standing as “ calva Co. ” and later labelled “ cf. radius ” by B. Verdcourt. Assuming that the latitude refers to a point south rather than north of the equator, the coordinates correspond to a point in the Taru Desert, ± 75 km inland of Malindi. RMNH.MOL.288087: 1 ad., near Mombasa (approx. 4.04°S, 39.66°E), amongst river debris, Sep. 1987.
Description
SHELL (Figs 6-8, 51). Large (4.00 - 4.60 mm high x 2.10 - 2.50 mm wide), of 6.5 - 8.0 whorls. Ovateacuminate, but more columnar than other Dadagulella gen. nov., spire narrowly to broadly acuminate (spire angle 49 - 62°). Apex pointed. Embryonic whorls smoothly granulate. Later whorls with characteristically coarse, few and widely spaced ribs (5 - 10 per mm on penultimate whorl). Sutures deep. Umbilicus closed or nearly so. Peristome incomplete parietally. Outer palatal surface of aperture with a depression corresponding to the palatal tooth. Dentition characteristically simple, 4-fold to 5-fold, consisting of: one lamella-like parietal tooth; one slab-like palatal tooth without parieto-palatal sinus; one basal denticle; and one deep-set columellar baffle, always visible, sometimes with a very slight, shallower columellar tooth. Juvenile shells and anatomy unknown.
Range and habitat
Lowlands of extreme southeastern Kenya, including Taru Desert. This subspecies has also been recorded from Malindi (Verdcourt 1962: 17) and Mrima Hill (4.48°S, 39.25°E) (Verdcourt 2006). Verdcourt (2000) suggested the habitat was “bushland to forest”, in contrast to “woodland/forest” for D. r. radius comb. nov. Shells of both D. r. radius comb. nov. and D. r. calva comb. et stat. nov. have been found in river debris near Mombasa, but may have been washed in from different localities.
Remarks
The lectotype and similar material of this subspecies (Figs 6-8, 51) differ from D. r. radius comb. nov. in the more widely spaced ribs, more columnar shape and simpler dentition, although some specimens seem to show intermediate characters. Verdcourt evidently had difficulty separating them. Although Verdcourt (1962: 17) suggested G. calva was “scarcely more than a variety of G. radius ”, it keyed out in a separate part of his key, with radius appearing in two other places (1962: 13, 22). The second of these (p. 22) was listed as “ Gulella radius (Preston) var. (K [Kenya], Mrima Hill Forest)”. Verdcourt’s measurements, description, and range of apertural tooth formulas allow attribution of this taxon to D. r. calva comb. et stat. nov .. In his later checklists, Verdcourt (1983: 234; 2006: 48-49) maintained the two as separate species, and gave Mrima Hill as a locality for calva but not radius. He also kept them apart in his list of coastal molluscs (2000). Thus it appears likely that he later decided that (1962: 22) “ radius var.” belonged to what we treat as D. r. calva comb. et stat. nov. and not to what we treat as D. r. radius comb. nov. It also appears that he decided not to separate the two taxa. We too found this a difficult decision to take, owing to the morphological, habitat and distributional differences, which may of course be interrelated. To acknowledge this difficulty, and the potential difficulties in assigning future material to either, we rank calva as a subspecies of radius.
description: Published as part of Rowson, Ben & Tattersfield, Peter, 2013, Revision of Dadagulella gen. nov., the " Gulella radius group " (Gastropoda: Streptaxidae) of the eastern Afrotropics, including six new species and three new subspecies, pp. 1-46 in European Journal of Taxonomy 37 (37) on pages 9-11, DOI: 10.5852/ejt.2013.37, http://zenodo.org/record/3806770