Search

In 1990, Emberton hypothesized that the Madagascan land snail Helix covani Smith, 1879 was a previously unrecognized member of the Gondwanan family Rhytididae. The evidence put forward was based solely on features of the shell. The present paper sets out to explore this hypothesis in more detail, using morphological characters of the soft parts and molecular data, and so to test whether the presentday distribution of the Rhytididae includes Madagascar, a biogeographically interesting question. The results obtained from several independent suites of morphological characters are clearly inconsistent with the placement of Helix covani in the Rhytididae. Instead, the morphological evidence strongly supports its referral to the Acavidae, with affinity to the genus Ampelita, in which it has traditionally been classified. Molecular data are fully consistent with this, providing strong support for an acavid clade comprising Acavus, Ampelita, Helicophanta and Helix covani. Currently, the morphological and molecular data available are not sufficiently representative of Madagascan acavid diversity to permit further resolution of the affinities of the taxon in relation to Ampelita and Helicophanta.

Ampelita decaryi Fischer-Piette, 1952 Fig. 13 Ampelita decaryi: Fischer-Piette 1952: 13, pl. 1, figs 7–9; Emberton 1990: fig. 4d, 1994: 176; Fischer-Piette et al. 1994: 97, pl. 7, figs 4–16. Type loc.: Madagascar. Locality data: Antsingimavo: st’n 04/06. Kelifely Plateau: st’ns 08/05, 10/05. Tsingy de Bemaraha: st’n 15/96. Distribution: Restricted to central western Madagascar; currently recorded only from Tsingy de Bemaraha and Antsingimavo. Not yet recorded from Tsingy Beanka, but known in subfossil form from the Kelifely Plateau. A record from the Ambositra area (Emberton 1994) almost certainly represents A. caderyi (see below). Habitat: Dry mixed deciduous-evergreen forest on karst outcrops. No living specimens found, but considerable numbers of empty shells were collected from slots within the tsingy and under overhangs. Remarks: The holotype of this species had no provenance beyond ‘Madagascar’, but Fischer-Piette (1952) mentioned a young individual from ‘Antsingy (Madagascar Ouest)’. Emberton (1990) and Fischer-Piette et al. (1994) placed this locality in the region of Tsingy de Bemaraha and additional material has since been found there (Griffiths, st’n 15/96). Emberton (1994) also identified under this name specimens from non-calcareous, rain forest habitats in the Ambositra area (Fianarantsoa Province). However, in reality this latter material is more probably referable to A. caderyi FischerPiette et al., 1994, the type locality for which lies in the same vicinity. Although they are undoubtedly similar, the differences between the two taxa were clearly stated by Fischer-Piette et al. (1994). In terms of shape and coloration, the Antsingimavo material closely resembles the holotype of A. decaryi figured by Fischer-Piette (1952). However, whilst some adult shells in the Antsingimavo population match the holotype in size (max. diameter 35mm), most are somewhat larger (max. diameter reaching 42 mm). The abundance of empty shells indicates that the species was once not uncommon at this locality. Though much of this material is clearly old, some specimens were of fresh appearance and retained the periostracum, indicating that the species is probably still extant at the site, even though we found no live specimens during our survey. Subfossil shells from the Kelifely Plateau (Fig. 13G) are indistinguishable from the Antsingimavo material, except that the colour pattern is much faded., Published as part of Griffiths, O. L. & Herbert, D. G., 2013, New species of land snails (Mollusca: Gastropoda) from two isolated karst formations in central western Madagascar: Tsingy Beanka and Antsingimavo, with additional notes on other regional endemics, pp. 1-48 in African Invertebrates 54 (1) on pages 20-21, DOI: 10.5733/afin.054.0101, http://zenodo.org/record/7670100, {"references":["EMBERTON, K. C. 1990. Acavid land snails of Madagascar: subgeneric revision based on published data (Gastropoda: Pulmonata: Stylommatophora). Proceedings of the Academy of Natural Sciences of Philadelphia 142: 101 - 117."]}

Ampelita namerokoensis Fischer-Piette, 1952 Figs 17E, 17F, 19, 20, 25F Ampelita namerokoensis: Fischer-Piette 1952: 35, pl. 3, figs 35–39; Fischer-Piette et al. 1994: 123, pl. 15, figs 5–8. Type loc.: ‘ Gorges de Salapango [= Salapanga], Bemaraha’, Madagascar. Morphological notes: External features (Fig. 25F): Head-foot mostly dark grey-brown with uniformly granular skin texture; optic tentacles slightly paler, running into similarly pale bands along neck; skin granules with microscopic ochre-brown pigment granules; lining of mantle cavity with some black pigmentation (not dense) and a pattern of pale circular blotches. Distal genitalia (Fig. 20): Resembling those of A. beanka, but differing considerably in penis morphology, particularly its internal structure. Penis shorter (ca 3.2 mm) and more slender than in A. beanka, and the apical region less swollen; vas deferens follows a similar path alongside penis, running to its apex and then recurving before inserting subterminally via a short, somewhat broader, pale flesh-coloured epiphallus; details of recurved vas deferens and epiphallus mostly concealed by attachment of retractor muscle. Interior of penis with a small conical papilla at insertion of epiphallus, from which a single mid-line fold runs to penis base; additional concentric folds surround papilla on both sides, these converging and evanescing toward penis base; the resultant pattern of folds differing considerably from that of A. beanka. Locality data: Tsingy Beanka: st’ns 03/06, 11/06, 12/06, 14/06, 16/06, 18/06, 02/09, 06/09, 07/09, 08/09, 09/09, 11/09, 01/10, 02/10, 05/10, 07/10, 08/10, 09/10, 10/10. Bemaraha: st’ns 14/95, 09/96, 12/96. Distribution: Restricted to central western Madagascar, with reliable records only from the Tsingy de Bemaraha and Tsingy Beanka; not found at Antsingimavo and, despite its name, evidently does not occur in Nameroko [Namoroka] (see Remarks below). Habitat: Living specimens are found most commonly amongst limestone rocks and in leaf-litter. In Tsingy Beanka, it occurs mostly in the southern region, in taller, moister forests. Remarks: Shell lenticular, of moderate size (max. diameter A. milloti.At this stage its identity remains puzzling. Further subfossil or very old dead specimens from limestone caves in the Anjajavy– Narinda area, northeast of Mahajanga (Griffiths pers. observ.) may also be referable here., Published as part of Griffiths, O. L. & Herbert, D. G., 2013, New species of land snails (Mollusca: Gastropoda) from two isolated karst formations in central western Madagascar: Tsingy Beanka and Antsingimavo, with additional notes on other regional endemics, pp. 1-48 in African Invertebrates 54 (1) on pages 27-29, DOI: 10.5733/afin.054.0101, http://zenodo.org/record/7670100

Ampelita andriamamonjyi sp. n. Fig. 12 Etymology: Named for Aldus Andriamamonjy, Executive Director of Biodiversity Conservation Madagascar that manages and protects the forests of the Tsingy Beanka. Diagnosis: Shell lenticular, periphery rounded; aperture strongly descendant; umbilical width moderate; whitish to fawn, characteristically patterned with 3 or 4 dark brown spiral bands, 1 or 2 above periphery, 2 below; sculpture of close-set, incised spiral striae; apertural rim reflected. Description: Shell: Medium sized, lenticular (H:D= 0.489 –0.586); whorls slightly flattened, periphery rounded; suture weakly indented, final part of last adult whorl descending conspicuously prior to aperture; umbilicus of moderate width, steep-sided and distinctly narrower internally. Protoconch of ca 1½–2¾ whorls, superficially etched in most specimens but some individuals with evidence of fine, close-set spiral threads on last whorl; junction with teleoconch usually ill-defined. Teleoconch of a further 2¼ whorls; sculptured by numerous, close-set, incised spiral striae; striae crossed by frequent fine, irregular growth-lines rendering the former wavy; basal sculpture similar, but weakening at umbilical rim and evanescing within. Aperture elongate-ovate, strongly oblique to vertical axis of shell; peristome incomplete, interrupted in parietal region, elsewhere its rim reflected, forming a flaring lip. Shell somewhat glossy; embryonic whorls buffish brown, slightly darker below suture; first teleoconch whorl with two dark brown spiral bands, lower one broad, situated just above abapical suture, the other narrower, lying a short distance below adapical suture; interval between upper brown band and suture almost white; upper brown band usually fading and disappearing with growth (sometimes within first half whorl), but persisting throughout in some individuals; ground colour becoming paler with growth, a rather uneven dirty white on last adult whorl; base with two further dark brown spiral bands, one just below periphery (emerging close to insertion of outer lip), the other midway between this and umbilical rim; ground colour between supra- and sub-peripheral brown lines paler, almost white; pale subsutural zone persisting throughout.Aperture lip white, colour bands clearly visible internally. Dimensions: Holotype (largest specimen), max. diameter 29.3 mm, height 15.1mm. Holotype: MADAGASCAR: Central W Madagascar, ca 60 km E of Maintirano, southern part of Tsingy Beanka, S side of Tana–Maintirano road, in tall moist forest growing on limestone on south-facing slopes, above N bank of Kimanambolo River, 18.06178°S 44.52494°E, ca 330 m, iv.2010, R. Randalana, st’n R02/10 (AMS C.474164). Paratypes: Same data as holotype (TMAM T162, 1 adult specimen); st’n R03/98 (NMSA L8441 /T2657, 2 adult specimens); st’n 04/06 (AMS C.469582, 1 adult specimen); st’n 16/06 (NMSA L7128 /T2656, 1 subadult specimen); st’n R04/09 (MNHN IM-2010-20070, 1 adult specimen); st’n R01/10 (AMS C.469581, 3 adult specimens). Additional locality data: Tsingy Beanka: st’ns 13/06, 16/06, 02/09, 08/09 (subfossil), R04/09, R01/10. Distribution: Fresh material has been found only in the Tsingy Beanka.A single subfossil shell is known from Antsingimavo, but the species is now perhaps extinct there. Not recorded from the Tsingy de Bemaraha. Habitat: Fresh dead shells found most commonly in and amongst limestone rocks, predominantly in the taller moister forests of the southern part of Tsingy Beanka. Not yet found alive. Remarks: Compared to other spirally banded Ampelita species, the banding pattern of A. andriamamonjyi is distinctive. A. akoratsara Emberton, 1999 (from Marojejy in far north-eastern Madagascar) has a somewhat similar pattern of dark brown spiral lines with whitish subsutural and peripheral bands, but it has a sharply keeled body whorl and lacks the mid-basal brown spiral band of A. andriamamonjyi. Unlikely to be confused with any other known Ampelita species., Published as part of Griffiths, O. L. & Herbert, D. G., 2013, New species of land snails (Mollusca: Gastropoda) from two isolated karst formations in central western Madagascar: Tsingy Beanka and Antsingimavo, with additional notes on other regional endemics, pp. 1-48 in African Invertebrates 54 (1) on pages 18-19, DOI: 10.5733/afin.054.0101, http://zenodo.org/record/7670100

Ampelita beanka sp. n. Figs 15, 16, 17A, 17B Etymology: Named after the type locality, Tsingy Beanka. Diagnosis: Profile distinctive due to low spire, strongly shouldered whorls and descendant suture; umbilicus wide; protoconch with close-set axial riblets; teleoconch with close-set lamellate axial pliculae; lustreless, more or less uniformly mid to dark brown. Description: Shell: Relatively small with sharply angled periphery situated well above mid-whorl; spire very low, frequently almost flat; apical surface of whorls weakly convex, becoming slightly concave toward periphery; suture shallowly indented, but progressively descending below peripheral keel on last adult whorl giving shell a stepped profile; umbilicus wide, its rim roundly angular. Protoconch of 1¼–1½ whorls, max. diameter variable 3.7–4.1 mm; initially smooth, rather flat and somewhat sunken, thereafter more convex, bearing numerous, close-set, curved, axial riblets; riblets occasionally bifurcating or anastomosing (Fig. 17A). Teleoconch of a further 2–2¼ whorls; sculptured by closeset, axial pliculae, each with a thin periostracal crest in living specimens, rendering the pliculae somewhat lamellate (Fig. 17B); growth irregularities frequent; basal sculpture the same, continuing into umbilicus. Aperture rounded basally, somewhat angled at periphery and flattened above this; strongly oblique to vertical axis of shell; peristome incomplete, interrupted in parietal region; rim of peristome slightly thickened and flaring in adult, more strongly so basally. Shell lustreless with a well-developed, predominantly mid to dark brown periostracum when fresh; slight radial unevenness in intensity; apical whorls often slightly paler; umbilicus commonly darker internally, its margin sometimes delineated by a paler band, but this rarely evident in fresh material. Dimensions: Holotype, max. diameter 17.7 mm, height 8.0 mm; largest specimen, max. diameter 19.1 mm. External features: Data on coloration of living animals not available; in preserved specimens head-foot mostly dark brown to blackish, but with evidence of a paler longitudinal band extending down neck from each optic tentacle; skin texture uniformly granular; lining of mantle cavity heavily pigmented with black and patterned with pale circular blotches, mostly on the right (upper) side. Distal genitalia (Fig. 16): Relatively simple and largely typical of the genus. Penis short to moderate in length (4.0–5.0 mm) and rather stout; vas deferens running beside and loosely attached to its basal portion, but becoming more closely attached near penis apex; at apex of penis vas deferens turns sharply back on itself and broadens noticeably before inserting some distance below penis apex; this latter portion, perhaps constituting an epiphallus, has a thicker, pale flesh-coloured wall and is fused to outer wall of penis. Penis retractor muscle attaches apically, enveloping recurved portion of vas deferens and penis apex. Interior of penis with a Y-shaped longitudinal fold in the centre of which is a distinct, rounded papilla at insertion of epiphallus; this primary fold bordered on each side by a further longitudinal fold; remainder of lumen largely smooth, but with evidence of microscopic papillation in apical region. Genital atrium and vagina, simple and short; bursa copulatrix duct long, basal portion somewhat broader; bursa itself of moderate size, ovate to subcircular. Holotype: MADAGASCAR: Central W Madagascar, ca 60 km E of Maintirano, in tall dense dry forest growing above cliffs on E side of Tsingy Beanka at Andohanandranogedro, 18.05028°S 44.53786°E, 380m, iv.2009, R. Randalana, st’n R04/09 (AMS C.474166, body in alcohol). Paratypes: Same data as holotype (NMSA L8504 /T2983, 9 specimens, bodies in alcohol; NHMUK 20120014, 1 specimen); st’n 07/10 (NMSA L8525 /T2980, 6 specimens); st’n 07/09 (NMSA L8501 /T2981, 4 specimens, one in alcohol); st’n R01/09 (NMSA L8507 /T2982, 2 specimens); st’n 01/10 (AMS C.469583, 4 specimens; TMAM T165, 1 specimen); st’n 09/09 (MNHN IM-2010-20071, 1 specimen). Additional locality data: Tsingy Beanka: st’ns 11/06, 09/09, 01/10. Distribution: A narrow-range endemic currently recorded only from Tsingy Beanka. Habitat. Fresh dead shells found most commonly in and amongst limestone rocks predominantly in the taller moister forests. Living individuals usually found in leaf-litter. Remarks: In terms of its shape and coloration, A. beanka resembles A. milloti and A. namerokoensis (below), both of which occur in the Bemaraha-Beanka region. A. namerokoensis differs in lacking significant axial sculpture on the protoconch and in having distinct spiral microsculpture on the teleoconch (Fig. 17E, F). It also attains a larger size, has the peripheral keel closer to mid-whorl, has a somewhat narrower umbilicus, and the suture, if descendant at all, is at most weakly so and then only near the end of the last adult whorl. Ampelita milloti is perhaps more similar in having axial riblets on the protoconch and lacking spiral microsculpture, but its teleoconch sculpture is finer, the axial elements more irregular and fragmented, appearing granular rather than lamellate (particularly evident on the base). Furthermore, as in A. namerokoensis, the suture of A. milloti is never strongly descendant. The smaller size, shouldered profile, strongly descendant suture and lamellate axial sculpture of A. beanka render it distinctive. The descent of the suture below the peripheral keel, though characteristic of the species and well developed in the holotype, is somewhat variable in its extent, but usually commences at least one half whorl prior to the aperture. The position of the peripheral keel is also somewhat variable, lying closer to mid-whorl in some specimens (Fig. 15D). We have considered the possibility that these differences may reflect ecological factors and that the stepped profile may result from damage to the mantle edge at the suture, as is evident in some specimens of both A. milloti and A. namerokoensis. However, the stepped profile of A. beanka is present in specimens showing no growth scars indicative of earlier damage to the outer lip, and we can consistently discriminate between A. beanka and the other two species in terms of the microsculptural differences detailed above. There are also significant differences evident in the morphology of the penis (see below). All three species occur in the Tsingy Beanka and have been found to cooccur at a number of sampling sites. Emberton (1999) described a similar lamellar axial microsculpture in A. analamerae Emberton, 1999, from far north-eastern Madagascar, but that species is larger, is keeled at mid-whorl and has a much more prominent spire and narrower umbilicus., Published as part of Griffiths, O. L. & Herbert, D. G., 2013, New species of land snails (Mollusca: Gastropoda) from two isolated karst formations in central western Madagascar: Tsingy Beanka and Antsingimavo, with additional notes on other regional endemics, pp. 1-48 in African Invertebrates 54 (1) on pages 23-26, DOI: 10.5733/afin.054.0101, http://zenodo.org/record/7670100

Ampelita milloti Fischer-Piette, 1952 Figs 17C, 17D, 18, 25E Ampelita milloti: Fischer-Piette 1952: 34, pl. 3, figs 31–34; Fischer-Piette et al. 1994: 123, pl. 15, figs 1–4. Type loc.: ‘ Gorge de Salapango [= Salapanga], Bemaraha’, Madagascar. Morphological notes: External features (Fig. 25E): Head-foot uniformly dark, charcoal-grey to black; skin texture uniformly granular throughout; lining of mantle cavity heavily pigmented with black and patterned with pale circular blotches (observations based on a single livecollected individual). Distal genitalia: The single preserved specimen available (shell diameter 19.2 mm) possessed an immature reproductive tract. The distal genitalia were thus poorly developed and inadequate for comparative study. From what could be seen of the penis, it appeared similar to that of A. namerokoensis. Locality data: Antsingimavo: st’ns 4/06, 8/06 (all subfossil). Tsingy Beanka: st’ns 12/06, 14/06, 16/06, 18/06, 02/09, 06/09, 07/09, 08/09, 01/10, 06/10, 07/10, 08/10, 09/10. Tsingy de Bemaraha: st’ns 07/95, 10/95, 14/95, 18/95, 19/95, 9/96, 10/96, 12/96. South bank of Tsiribihina River: st’ns 01/99LP, 02/99LP. Distribution: Evidently a narrowly endemic species, currently known only from the south bank of Tsiribihina River, Tsingy de Bemaraha and Tsingy Beanka. Subfossil at Antsingimavo where it now appears to be locally extinct. Habitat: Living specimens are most commonly found amongst limestone rocks and in leaf-litter. In Tsingy Beanka, it occurs predominantly in the taller, moister forests of the southern part. Remarks: Shell lenticular, of moderate size (max. diameter vs 28–32 mm). Resembles A. namerokoensis (below) in size and shape, but easily separated from that species due to the almost complete absence of microscopic spiral striae (some traces may be visible on the base). Instead the microsculpture of A. milloti comprises irregular, elongate granules aligned in a roughly radial (collabral) pattern (Fig. 17D). Furthermore, A. milloti attains a somewhat larger size and has a wider umbilicus than A. namerokoensis, and its protoconch is larger (diameter approx. 4.4 vs approx. 3.5 mm) and bears distinct close-set axial riblets (Fig. 17C), whereas that of A. namerokoensis is more or less smooth (Fig. 17E). Features separating A. milloti from A. beanka are discussed above., Published as part of Griffiths, O. L. & Herbert, D. G., 2013, New species of land snails (Mollusca: Gastropoda) from two isolated karst formations in central western Madagascar: Tsingy Beanka and Antsingimavo, with additional notes on other regional endemics, pp. 1-48 in African Invertebrates 54 (1) on pages 26-27, DOI: 10.5733/afin.054.0101, http://zenodo.org/record/7670100

Ampelita lindae sp. n. Fig. 14 Etymology: Named for Linda Davis, manager of the Mollusca collection at the KwaZuluNatal Museum and one of the members of the team that discovered this species. Diagnosis: Shell discoidal, spire flat or nearly so, periphery rounded; aperture strongly descendant with reflected rim; umbilicus wide; surface rough, sculptured by raised collabral vermiform granules; lustreless, mid-brown with whitish, flake-like markings and a pale peri-umbilical band. Description: Shell: Medium sized, relatively thin, discoidal with very low spire (H:D= 0.357 –0.485); periphery at or just above mid-whorl, rounded or weakly angled; a very weak supraperipheral gutter evident in occasional individuals, particularly near start of last whorl; suture indented, final part of last adult whorl descending steeply prior to aperture; umbilicus wide, funnel-shaped. Protoconch of ca 1¼–1½ whorls, the first smooth, thereafter with numerous, irregular, axially elongate granules; junction with teleoconch ill-defined. Teleoconch of a further 2½ whorls; with irregular growth-lines and an uneven sculpture of raised vermiform granules, in a primarily collabral alignment (Fig. 14D); surface thus rendered rough to the touch; granules not simply periostracal, but present on underlying shell; this sculpture continues onto base and into umbilicus. Aperture elongate-ovate, strongly oblique to vertical axis of shell; peristome incomplete, interrupted in parietal region; rim of peristome reflected forming a flaring lip. Shell lustreless, covered with a predominantly mid-brown periostracum when fresh, with irregular, pale, flake-like markings; underlying shell mostly pale with darker brownish spiral bands either side of a pale, peri-umbilical band; sometimes also darker behind flared aperture lip. Aperture lip white, interior greyish brown in fresh material. Dimensions: Holotype, max. diameter 30.5 mm, height 12.6 mm; largest specimen, max. diameter 31.4 mm, height 12.7 mm. Holotype: MADAGASCAR: Central W Madagascar, ca 10 km NE of Belitsaka and ca 60 km E of Maintirano, E side of Tsingy Beanka, in leaf-litter and amongst limestone boulders in tall moist east-facing forest growing on limestone, above Bokarano River Cave, 17.90568°S 44.48822°E, ca 230 m, 29.x.2009, O. Griffiths, D. Herbert, L. Davis & R. Randalana, st’n 07/09 (AMS C.474167). Paratypes: Same data as holotype (NMSA L8468 /T2903, 1 adult specimen); st’n 07/10 (AMS C.469580, 3 adult specimens); st’n 09/10 (AMS C.469579, 1 adult specimen); st’n 07/10 (TMAM T163, 1 adult specimen). Distribution: Evidently a narrow-range endemic, currently known only from Tsingy Beanka; not yet known from either Tsingy de Bemaraha or Antsingimavo. Habitat: Known only from fresh dead shells collected in leaf-litter in tall, east-facing, evergreen forest in the central part of Tsingy Beanka. Remarks: With its relatively small, very depressed shell and rough, vermiform microsculpture, A. lindae is a distinctive species. A. granulosa (Deshayes, 1840) (from the north-eastern tip of Madagascar), another species with coarse microsculpture, is much larger and has distinct periostracal bristles arising from the granules, a feature not evident in the present species. Additional material resembling A. lindae has been found as subfossils in the Kasijy Forest (Kelifely Plateau). These are larger (max. diameter 32.9–35.0 mm, height 15.3– 17.9 mm) than the present material but are clearly morphologically close to it. The material available, however, is inadequate to permit thorough study and meaningful comparison.

Seven new land snail species are described from the Antsingimavo and Beanka karst formations, northeast of Maintirano, central western Madagascar: Ampelita andriamamonjyi, A. beanka, A. lindae, Conulinus randalanai, Kalidos maryannae, Tropidophora humbug and T. sericea. Additional notes, records and illustrations are also provided for a further ten regionally endemic species.

Ampelita (Eurystyla) griffithsi Emberton, 1999 Ampelita (Eurystyla) griffithsi: Emberton 1999: 91, figs 11, 12. Locality data: Tsingy Beanka: st’n R01/11. Distribution: Previously known from Kirindy (near Morondava) and the southern and central areas of the Tsingy de Bemaraha. Now known also from the southern Tsingy Beanka. Habitat: Deciduous scrub, semi-deciduous forest and riverine gallery forest (Emberton 1999). Remarks: The occurrence of A. griffithsi in riverine forest along the Namela River on the southern boundary of Tsingy Beanka Reserve represents a considerable northern range extension for the species., Published as part of Griffiths, O. L. & Herbert, D. G., 2013, New species of land snails (Mollusca: Gastropoda) from two isolated karst formations in central western Madagascar: Tsingy Beanka and Antsingimavo, with additional notes on other regional endemics, pp. 1-48 in African Invertebrates 54 (1) on page 21, DOI: 10.5733/afin.054.0101, http://zenodo.org/record/7670100

Nine species of Madagascan acavid land snails were compared in a phylogenetic context. The two most plesiomorphic, Clavator johnsoni and C. moreleti, differ from the others by their high-spired shells, short tentacles, short tails, long necks, and crawling mode of hitching the shell along the ground. In the seven more apomorphic species, the crawling mode is smooth, with the shell resting on the tail, and the relative lengths of tail and shell correlate significantly. Among these seven species, three pairs of closest relatives (Helicophanta petiti and H. vesicalis, H. farafanga and H. souverbiana, Ampelita decaryi and A. julii) show evidence of phylogenetic constraints on ranked shell size. Aestivation site (as tentatively inferred from rare data) does not correlate with shell shape or size: burrowers have H/D = 2.7 to 0.6 and D = 70 to 25 mm; arboreals have H/D = 0.8 to 0.5 and D = 70 to 30 mm; the species with both the highest spire and the smallest diameter (C. moreleti) is neither a burrower or an arboreal, but stays on the ground surface. Inferred aestivation sites are randomly distributed phylogenetically. Climate shows no correlation, except that the arboreals arc only from humid to wet regimes. Uniform shell colouration occurs only in burrowers (C. johnsoni, H. petiti, H. vesicalis), but disruptive shell colouration occurs in all others, including burrowers (H. farafanga, A. decaryi), ground-surface aestivators (C. moreleti), arboreals (H. souverbiana, A. julii), and semi-arboreals (Ampelita subfunebris). Among all nine species, burrowers have significantly thicker shells (than their close relatives of similar size), wider bodies, and longer snouts than non-burrowers (H. souverbiana is exceptional in being arboreal despite its huge size and in having the broad foot and snout of a burrower). Thus, although there is some evidence for phylogenetic constraints, natural selection for aestivation and crawling behaviours seems to have dominated the evolution of external body morphology and of shell thickness (but not shell size and shape) in these snails.