Megalobulimus amandus, 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

Megalobulimus amandus new species

( Figs. 22-26 )

Types: Holotype MZSP 103917 .

Paratypes: MZSP 103919 , 3 shells ; USNM, 1 shells; MNRJ, 1 shells; NMHN, 1 shells; MZSP 103918 , 10 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 less than 80 mm, tip pointed, spire acuminate. Protoconch bearing series of uniform, delicate axial cords. Shell walls relatively thick. Peristome simple, pink to red.

Description: Shell up to 80 mm; outline oval; apex acuminate; width ~60 of length, dorso-ventral height ~50% of shell length. Color mostly pale beige in periostracum-lacking specimens ( Figs. 22-25 ); some few specimens with periostracum ( Fig. 26 ) somewhat glossy, eroded, presenting mosaic of pale and dark brown bands randomly disposed axially; peristome red to pale pink. Protoconch of ~3 weakly convex whorls, forming a somewhat pointed dome with ~70°; first whorl mostly smooth, opaque, remaining whorls bearing much delicate, uniform, narrow axial cords, ~ 120 in last nepionic whorl ( Fig. 25 ); each cord running from suture to suture since second whorl, interval between cords very narrow; limit between protoconch and teleoconch barely clear, orthocline. Teleoconch of 2.2 to 2.5 whorls, first whorl with almost straight profile, last whorl more convex than preceding ones. Spite ~60% of shell length. Sculpture similar to that of protoconch, with cords becoming delicate, but well-marked undulations, ~ 60 in penultimate whorl; ~30% of specimens possessing hammer-like marks in last whorl mid-region ( Fig. 24 ) and region preceding peristome. Peristome complete, normally thick ( Figs. 22, 23 ), glossy, lacking tooth of folds; aperture elliptic, ~54% of shell width, ~50% of shell length. Outer lip simple and rounded. Inner lip feebly concave; no clear separation with callus and parietal region ( Figs. 22, 26 ). Umbilicus extremely narrow to absent.

Measurements (in mm): Holotype: 78.9 by 50.0; paratype MZSP 103919: (1) 69.8 by 40.2; (2) 25.6 by 17.6.

Distribution: Known only for type locality.

Habitat: Caatinga environment.

Material examined: Types.

Etymology: The specific epithet refers to the outline of the shell, resembling a drop. From the Tupi native language from South America, amanda or amana meaning rain or related to rain.

Discussion: Megalobulimus amandus clear belong to the informal complex Megalobulimus oblongus (Müller, 1774) as introduced by Simone & Leme (1998). This complex includes species with deciduous periostracum, peristome normally reddish, sculpture almost exclusively axial strong undulations, and a protoconch also only sculptured by clear axial, uniform undulations or narrow cords. This set of characters can be regarded as the definition of the genus Psiloicus Morretes, 1952 , in such M. amandus and remaining M. oblongus complex can someday belong after a deeper revision of the group. A conservative approach is given herein.

Only few of the 62 valid species of Megalobulimus have pointed shell apex ( Bequaert, 1948; Leme, 1973; Simone, 2006). This is one of the main characters of M. amandus , as most Megalobulimus in fact possess a more rounded, dome-shaped apex. For this reason, M. amandus only needs to be compared with species from M. oblongus complex with pointed apex. M. amandus differs from M. formicacorsii (Barattini & Ledón, 1949) , from Uruguay, in having aperture wider and longer, sculpture shallower, and umbilicus narrower or absent. It differs from M. maximus (Sowerby, 1825) , from Amazon, in being much shorter and smaller, by shallower suture, and by reddish peristome. It differs from M. riopretensis Simone & Leme, 1998 , from São Paulo, in having narrower aperture, narrower shell width, by more delicate protoconch and teleoconch sculptures, and by less developed umbilicus. It differs from M. wohlersi Morretes, 1952 , from Mato Grosso do Sul, by narrower shape, more elongated aperture, shallower suture, broader spire, and more delicate sculpture.

The megalobulimids from Northeastern Brazil normally possess a purple pigmentation in the protoconch and spire first whorls. This is not the case of M. amandus , which has uniform coloration. On the other hand, the species of that region are normally of small size for a Megalobulimus , i.e., below 80 mm, which is the case of the new species. Another interesting feature of M. amandus is the absence of folds and teeth in the peristome, even in more thickened specimens ( Figs. 23, 24 ). Tooth and folds in parietal callus or in middle level of outer lip are common occurrences in species from that region.

A conservative approach is given here considering the genus Megalobulimus in Megalobulimidae Leme, 1973 . However, it is recognized that the taxon can possibly be a special branch of Strophocheilidae , and even Acavidae . A project on this matter has been developed, mainly considering phylogenetic methodologies.

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).