Dadagulella minuscula minuscula ( Morelet, 1877 ) minuscula (Morelet, 1877

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, European Journal of Taxonomy 37, pp. 1-46 : 27-28

Dadagulella minuscula minuscula ( Morelet, 1877) comb. nov. Figs 38-39 , 62-63 , 84 ; Table 1

Pupa minuscula Morelet, 1877: 340 .

Pupa fischeriana Morelet, 1877 : pl. XII, fig. 5 (objective synonym).

Ennea fischeriana – Morelet 1881: 230-231. — Richardson 1988: 103 (objective synonym).

Ennea (Gulella) fischeriana – Tryon 1885: 100, pl. 20, fig. 39.

Ennea (Uniplicaria) fischeriana – Kobelt 1905: 166, pl. 22, fig. 10; 1910: 158.

Pupa minuscula – Kobelt 1905: 166; 1910: 158. — van Bruggen 1975: 166.

Ennea minuscula – Preston 1910: 529.

Gulella minuscula Morelet (non Gulella minuscula Emberton & Pearce, 2000 ) – Fischer-Piette & Vukadinovic 1974: 55. — Richardson 1988: 103. — Rowson 2007a: 441-442. — Rowson & Lange 2007: 31. — Muratov 2010: 277.

Type material examined

COMOROS: lectotype (here designated) and paralectotype NHMUK.1893.2.4.87-88: 2 ads, “ Anjouan I.” (Nzwani I., approx. 12.22°S, 44.45°E), labelled “ types ”. The smaller of the two specimens is apparently the shell figured in Morelet (1877: pl. XII, fig. 5) under the name “ fischeriana ”. It was evidently formerly on a white card mount. This shell is here designated lectotype, while the larger is considered a paralectotype (although Morelet’s description could in fact have been made from a single shell).

Type locality

“Dans l’île d’Anjouan (Johanna)” ( Morelet 1877; from title of paper).

Description

SHELL ( Figs 38-39 , 62-63 ). Variable in size, shape and dentition, small to large (3.00 - 4.10 mm high x 1.90 - 2.00 mm wide), of 6.5 - 7.0 whorls. Ovate-acuminate, spire broadly acuminate (spire angle 48 - 63°). Apex pointed. Embryonic whorls smoothly granulate. Later whorls with relatively fine, numerous ribs (10 - 13 per mm on penultimate whorl). Sutures relatively deep. Umbilicus closed or nearly so. Peristome complete, or incomplete parietally. Outer palatal surface of aperture with a depression corresponding to the palatal tooth. Dentition 4-fold (lectotype, Figs 38 , 62 ) to 5-fold (paralectotype, Figs 39 , 63 ), consisting of: one lamella-like parietal tooth; one slab-like palatal tooth, often bifid, but with parietopalatal sinus barely present; one basal denticle; and one deep-set columellar baffle, always visible. An additional shallow columellar denticle is present in the paralectotype. Shells and anatomy of juveniles unknown.

Range and habitat

Nzwani (Anjouan) island in the Comoros archipelago; habitat unknown.

Remarks

Morelet (1877) described this species from Anjouan (type locality implied by the paper’s title) under the name “ Pupa minuscula ” but figured it under the name “ Pupa fischeriana ” (pl. XII, fig. 5). In the paper he compared it to three species from “Île Bourbon” (Réunion), but none is very like it, suggesting Morelet was unaware of other Dadagulella gen. nov. species and probably meaning that D. m. minuscula comb. nov. was the first species of the group to be collected. Two of the Réunion species are streptaxids of the Mascarene genus Gonospira Swainson, 1840 while the third belongs to the Pupillidae Turton, 1831 (see Griffiths & Florens 2006). Although Kobelt (1905, 1910) classified D. m. minuscula comb. nov. (under fischeriana ) in the subgenus Ennea (Uniplicaria) L. Pfeiffer, 1856 , it is very unlike Pupa cerea Dunker, 1848 , the type species of Uniplicaria. Preston (1910) made a more relevant comparison in his description of Ennea radius , noting that his species had coarser ribs, a columellar denticle, and a bifid palatal tooth that were absent in D. m. minuscula comb. nov. Given these remarks and the fact that Preston cited only Anjouan as a locality for D. m. minuscula comb. nov., it thus appears he examined only the lectotype of the latter or material that was very like it. We agree that these features distinguish the lectotype of D. m. minuscula comb. nov. from that of D. r. radius comb. nov. However, the paralectotype (if it is such; see also below) of D. m. minuscula comb. nov., while having similarly fine ribs, has a stronger shallow columellar denticle that resembles that of D. r. radius comb. nov. Although we have seen no mainland specimen that exactly matches either of them, both specimens of D. m. minuscula comb. nov. fall within the range of variation seen in D. r. radius comb. nov. in other respects. It is therefore possible that the two taxa are synonymous, in which case Morelet’s name would take priority over Preston’s. It is even possible that D. minuscula comb. nov. s.l. consists of populations of D. radius comb. nov. s.l. derived from specimens introduced from the African mainland (the alternative, that D. radius comb. nov. s.l. was introduced into East Africa from the Comoros appears unlikely given the variation seen in East African populations and the many similar species there). That said, the isolated, volcanic Comoros archipelago comprises a region of endemism in itself and D. minuscula comb. nov. s.l. could easily be a Comoros endemic whose overlapping variation with D. radius comb. nov. s.l. is due to homoplasy. Resolving the relationships between these two taxa, and D. m. mahorana subsp. nov. below, is likely to require anatomical or molecular data. Until such information becomes available, and while we focus on other issues within Dadagulella gen. nov., we maintain the two species as separate. Van Bruggen (1986) took a similar approach with two other streptaxids, one described by Preston from the Shimba Hills, the other by Morelet from Mayotte.

There is a nomenclatural issue concerning the name minuscula Morelet, 1877 . Morelet (1881) tried to replace the name used for the (1877) description, Pupa minuscula , with the name used for the (1877) figure, Ennea fischeriana . Morelet (1881) wrote that the name P. minuscula had been published in error. Subsequently both Tryon (1885: 100) and Kobelt (1905: 166; 1910: 158) accepted fischeriana as the species name. However, when revising the fauna of the Comoros, Fischer-Piette & Vukadinovic (1974) disagreed. They treated E. fischeriana is an objective synonym of P. minuscula since the latter was not preoccupied and was validly introduced. This point of view was followed by Richardson (1988). As a consequence, the lectotype of D. m. minuscula comb. nov. in NHMUK also becomes the lectotype of E. fischeriana and the latter name remains unavailable for a taxon founded on another specimen. This includes the paralectotype, which is further discussed below.

Finally, we note that, although Emberton & Pearce (2000) described a junior homonym of minuscula Morelet, 1877 in Gulella ( G. minuscula Emberton & Pearce, 2000 ) no replacement name is required since minuscula Morelet is here transferred from Gulella to Dadagulella gen. nov.

Figures

Figs 36-40. Adult shells of Dadagulella gen. nov. species. 36. D. selene (van Bruggen & Van Goethem, 1999) comb. nov., holotype, Virunga NP (after van Bruggen & Van Goethem 1999). 37. D. meredithae (van Bruggen, 2000), holotype, Nyika NP. 38. D. minuscula minuscula (Morelet, 1877), lectotype, Nzwani. 39. D. minuscula minuscula, paralectotype, Nzwani. 40. D. minuscula mahorana subsp. nov., holotype, Mayotte.

Figs 51-64. Apertures of adult shells of Dadagulella gen. nov. species (not to scale). 51. D. radius calva, lectotype, Taru Desert. 52. D. radius radius, lectotype, Shimba Hills. 53. D. radius radius, Amboni. 54. D. browni mafiensis subsp. nov., holotype, Mlula. 55. D. browni semulikiensis subsp. nov., holotype, Semuliki NP. 56. D. ecclesiola sp. nov., holotype, Kimboza (two views of shell showing basal tooth only visible when shell angled). 57. D. cresswelli sp. nov., holotype, Ngorongoro. 58. D. minareta sp. nov., holotype, Kimboza. 59. D. cuspidata comb. nov., holotype, Shume (note shell angled slightly differently to that in Fig. 31). 60. D. pembensis sp. nov., holotype, Ngezi. 61. D. frontierarum sp. nov., holotype, Mtai. 62. D. minuscula minuscula, lectotype, Nzwani. 63. D. minuscula minuscula, paralectotype, Nzwani. 64. D. minuscula mahorana subsp. nov., holotype, Mayotte.

Fig. 84. Distribution of Dadagulella gen. nov. species, based on published records and material examined here (for additional records of D. meredithae comb. nov. in northern Malawi see van Bruggen 2000). The inset on the left corresponds to the map on the right.