Dadagulella browni mafiensis, Rowson & Tattersfield, 2013

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 : 13-14

Dadagulella browni mafiensis subsp. nov.

Figs 21 , 54 , 84 ; Table 1

Etymology

From Mafia Island, with the final ‘a’ elided for euphony.

Type material examined

NHMUK.20110174: 1 ad., Mlula, Mafia I. (approx. 7.87° S, 39.76° E), evergreen coastal thicket on clay loam coral rag, leg. Frontier Tanzania, Oct.- Nov. 1990, labelled “ Gulella radius aggreg.” by B. Verdcourt.

Other material examined

None.

Description

SHELL ( Figs 21 , 54 ). Small (3.30 mm high x 1.80 mm wide), of 6.0 whorls. Ovate-acuminate, spire broadly acuminate (spire angle 65°). Apex conical. Embryonic whorls smoothly granulate. Later whorls with relatively coarse ribs (12 per mm on penultimate whorl). Sutures relatively shallow. Umbilicus narrowly open. Peristome incomplete parietally. Outer palatal surface of aperture with a depression corresponding to the palatal tooth. Dentition 5-fold, consisting of: one lamella-like parietal tooth and one additional parietal denticle; one slab-like palatal tooth, forming a narrow parieto-palatal sinus; one basal denticle; and a deep-set, folded columellar baffle, but no shallower columellar denticles. Shells and anatomy of juveniles unknown.

Range and habitat

Evergreen coastal thicket at the type locality.

Remarks

This taxon is in some respects intermediate between the type specimens of D. r. radius comb. nov. and D. b. browni comb. nov., and thus distinct from either, yet difficult to place. It is larger and not as squat as other D. browni comb. nov. s.l., and lacks the additional basal denticle and shallower columellar dentition. Conversely, it has a parietal denticle not seen in D. radius comb. nov. s.l, is smaller and squatter than most D. radius comb. nov. s.l., and has a longer and narrower parieto-palatal sinus than any D. radius comb. nov. s.l. Mafia Island, from which no other Dadagulella gen. nov. are yet known, lies at almost the same latitude (7.8°S) as the apparent northernmost limit of D. b. browni comb. nov. in mainland Tanzania. Given the morphology of this specimen, its latitude and its isolation as an island population, we treat it as a subspecies of D. browni comb. nov.

Figures

Figs 6-26.Adult shells of Dadagulella radius (Preston, 1910) comb. nov., D. browni (van Bruggen, 1969) comb. nov. and their respective subspecies. 6-20. D. radius comb. nov. s.l. 6-8. D. radius calva (Connolly, 1922): 6. Lectotype, Taru Desert. 7. Taru Desert near Malindi. 8. Near Mombasa. 9-20. D. radius radius: 11. Lectotype, Shimba Hills. 12. Gazi. 13. also Gazi. 14. Diani Beach. 15. Amboni. 16. Kimboza. 17. Mkungwe. 18. Pugu. 19. Mbudya I. 20. Jozani. 21-26. D. browni comb. nov. s.l.: 21. D. browni mafiensis subsp. nov., holotype, Mlula. 22. D. browni semulikiensis subsp. nov., holotype, Semuliki NP. 23-26. D. browni browni: 23. Mwanihana. 24. Mzelezi. 25. Pomene Bay. 26. Holotype, Lake Sibayi (after van Bruggen 1969).

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.