Anostoma tessa, Simone, 2012

Simone, Luiz Ricardo L., 2012, Taxonomical Study On A Sample Of Pulmonates From Santa Maria Da Vitória, Bahia, Brazil, With Description Of A New Genus And Four New Species (Mollusca: Orthalicidae And Megalobulimidae), Papéis Avulsos de Zoologia 52 (36), pp. 431-439 : 431-439

Anostoma tessa new species

( Figs. 15-20 )

Types: Holotype MZSP 103914 .

Paratypes: MZSP 103915 , 1 shell ; USNM, 2 shells; MNRJ, 2 shells; NMHN, 2 shells; MZSP 103916 , 37 shells; all from type locality .

Type locality: BRAZIL. Bahia; Santa Maria da Vitória , ~ 13°24’S, 44°12’W, ~ 460 m of elevation (Coltro col., i/2012) .

Diagnosis: Shell with tall spire (spire ~60% of length). Aperture wide, with tall teeth. Anal canal well-developed, turned backwards. Callus reaching shell apex.

Description: Shell discoid, lenticular, up to 32 mm. color white, with irregular small spots sometimes coalescent, forming barely bands in rather spiral pattern ( Figs. 16, 18 ). Spire ~55% of length and ~40% of height. Protoconch simple, almost plane, white, opaque; 1.5 weakly convex whorls; limit with teleoconch unclear; occupying ~10% of shell length and almost zero of its height ( Figs. 15, 18, 20 ). Teleoconch with ~4.5 whorls; whorls weakly convex, suture shallow; in conjunct whorls forming wide dome. Sculpture weak, mainly constituted by axial undulations, ~ 33 in penultimate whorl; body whorl with delicate hammer-like marks in periphery in ~50% of specimens, and weak axial undulations; inferior surface (fig. 16) possessing weak axial undulations with scanty delicate hammer-like marks. Peripheral carina very weak, almost absent ( Figs. 17, 18 ), mainly visible in opposite side than aperture. Pair of wide furrows gradually appearing ~20% of shell length posterior to peristome in dorsal surface of pre-peristome region ( Figs. 16, 17 ); both ending in wide furrow formed by peristome expansion ( Fig. 16 ). Peristome complete, thick, mainly in outer lip ( Figs. 15, 19, 20 ), occupying from ~72 to ~60% of shell width and ~30% of shell length; 5 complete teeth, somewhat similar and equidistant with each other; height of each tooth ~50% of aperture width and about as wide as peristome lip; all teeth arched, with concavity turned to right or posteriorly; anal canal well distinct ( Figs. 15, 19, 20 ), flanked by pair of folds, posterior fold simple, curved, thin and relatively low, located somewhat perpendicularly to right parietal tooth, anterior fold double, in conjunct somewhat similar to posterior tooth, except in being situated more obliquely. Anal canal clearly tuned backwards, ~40-45° in relation to longitudinal axis of shell. Callus thin, rounded, simple, reaching shell apex or close to it ( Figs. 15, 18, 20 ).

Measurements (in mm): Holotype: 31.1 by 24.5; paratype MZSP 103915: 31.1 by 23.5.

Distribution: Known only for type locality.

Habitat: Caatinga environment.

Material examined: Types.

Etymology: The specific epithet refers to the Tupi native language in such tessa means eye, an allusion for the form of the shell.

Discussion: Anostoma tessa is only similar to Anostoma baileyi Solem, 1956 , the single species so far possessing a clear demarcated anal canal at aperture, but it differs in having this anal canal turned posteriorly, while that of A. baileyi is turned right of even anteriorly; in having a taller spire (spire is ~55% of length, while it is ~45% in A. baileyi ); in having wider callus, reaching the shell apex (while the callus of A. baileyi covers slightly more than half of distance between inner lip and shell apex). The other Anostoma -like species that are also anal canal bearing is Ringicella luetzelburgi Weber, 1925 , in such the new species differ in having much less developed apertural teeth, wider aperture, broader callus and taller spire. Most species of the genus Ringicella Gray, 1847 possess anal canal, but, different from that of Anostoma species that bear the canal, the structure forms a tube, opening separately from the shell aperture ( Simone, 2006:175, fig. 622).

Anostoma tessa apparently is the broader and more inflated from the Anostoma-Ringicella species, this being a most distinctive feature of the new species. Besides, the presence and form of the anal canal is another exclusivity, it is a quite rare among the Anostoma (only a single species bears it), and it is the rule in Ringicella , but separated in a proper tube. In this feature, A. tessa and A. baileyi are somewhat intermediary between a typical Anostoma and the Ringicella .

Figures

FIGURES 15‑26: Shell of types and ordinary specimens: 15-20) Anostoma tessa new species; 15) Holotype, apertural view (H 31.1 mm); 16) Same, dorsal view; 17) Same, left view; 18) Same, right view; 19) Same, detail of aperture, apertural-slightly anterior view; 20) Paratype MZSP 103915, apertural view (H 31.1 mm); 21) Rhinus suturalis, MZSP 103924, frontal view (H 23.6 mm); 22-26) Megalobulimus amandus new species; 22) Holotype, apertural view (H 78.9 mm); 23) Same, right view; 24) Same, dorsal view; 25) Paratype MZSP 103919(2), young specimen, apical (larger) and apertural view (H 25.6 mm); 26) Paratype MZSP 103919(1), adult with thin lip, apertural and right views (H 69.8 mm).