Plagiodontes weyrauchi, Pizá & Cazzaniga, 2009
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publication ID |
https://doi.org/ 10.1080/00222930902903244 |
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persistent identifier |
https://treatment.plazi.org/id/E25D87A9-2267-351B-FDD9-AE24FDC6FF5A |
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treatment provided by |
Felipe |
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scientific name |
Plagiodontes weyrauchi |
| status |
sp. nov. |
Plagiodontes weyrauchi View in CoL sp. nov.
Plagiodontes pusillus Weyrauch , ca. 1968, in schedula (nomen nudum).
Plagiodontes multiplicatus elongatus Weyrauch , ca. 1968, in schedula (nomen nudum). Diagnosis
Shell greyish-brown, thin, quite translucent, elongate-cylindrical. Adults 16.7–22.3 mm long have a relatively smaller width (mean 40% of the shell length) and a higher number of whorls (8–9.75) than any other Plagiodontes species within its size range. Low proportion of the last whorl length (mean 57%) and aperture (mean 38%) to shell length. Aperture occluded by 10–12 teeth (lamellae + folds). Protoconch with axial costae crossed by straight spiral lines; teleoconch with straight, thin costae. Ureteric pore opening at the level of the upper third of the kidney. Genital system of proportionally small size (19–22 mm long). Penis papillae (verge) with a small accessory lobe. Inner surface of the vagina with parallel long lamellae that rarely show some weak anastomosis.
Type series
Holotype, MACN-In 37,465 (alcohol-preserved specimen) 19 mm long, 8.4 mm wide; 5 paratypes, MACN-In 37,466 (3 shells and 2 specimens in alcohol); 5 paratypes, MLP 12,673 View Materials (3 shells) and MLP 12,674 View Materials (2 specimens in alcohol); 5 paratypes, FML 15,145 View Materials (3 shells) and FML 15,145 View Materials A (2 specimens in alcohol).
Type locality
Cuesta de la Chilca, 22 km to the East of Andalgalá on the Provincial Route 48 (27°38′19′′ S, 66°10′27′′ W), 1455 m above sea level, Catamarca province, Argentina GoogleMaps .
Other known localities
Villavil river , Andalgalá Department, Catamarca province, Argentina . Vipos (26°29′ S, 65°22′ W), Tucumán province, Argentina GoogleMaps .
Etymology
Dedicated to the late Dr Wolfgang K. Weyrauch (1907–1970). A short biography and a list of his malacological contributions were recently compiled by Barbosa et al. (2008).
Description
Shell elongate-cylindrical, greyish brown, thin (pulmonary vein, kidney and pericardium are visible by transparency in live and alcohol-preserved specimens) ( Figure 4). Spiral angle from 29° to 46°, major angle from 121° to 138°; 8–9.75 slightly convex whorls, the spire being about 40–46% the length of the shell, with a conical apex. Adult size ranging from 16.6 to 22.3 mm long, 7.1 to 9.0 mm wide. Narrowly perforated to rimate umbilicus ( Figure 5 View Figure 5 ). Shell variability is represented in Figure 6 View Figure 6 .
The protoconch has 2–2.5 whorls, with slightly undulated axial striae and some anastomoses in the first whorl ( Figure 7A,D View Figure 7 ); protoconch ribs are decussated by straight spiral lines ( Figure 7B View Figure 7 ). The limit between protoconch and teleoconch is well defined ( Figure 7D View Figure 7 ). The teleoconch presents a regular striation of thin but conspicuous axial costae ( Figure 7C,E View Figure 7 ).
Aperture 6.3–8.4 mm long, 5.3–7.4 mm wide, subvertical ovate with a thickened, expanded and slightly reflected adult peristome ( Figure 8B View Figure 8 ), partially occluded by 10–12 teeth (lamellae + folds) ( Figure 8A View Figure 8 ). The transverse lamella is long and straight. A tongue-shaped columellar lamella is the largest piece occluding the aperture; its outer border is thick and slightly elevated. A minute supracolumellar knob appeared on the columellar lamella of most specimens (97.5%). The parietal lamella is dihedral, its faces forming an L-profile; it is seen as a quadrangular plate when viewed from the apertural plane and it is sometimes united to the angular fold. Two suprapalatal folds are present; the upper one is usually triangular and the lower one is always compressed. The upper palatal lamella is rectangular, with the outer border thickened and elevated; its lateral borders are curved upwards. The lower palatal folds were present in all specimens, with 41% of specimens showing one and 59% showing two; when two lower palatal folds were present, the most developed one was that located next to the upper palatal lamella (principal lower palatal). The basal fold is laterally compressed and generally larger than the principal lower palatal fold.
Pallial complex ( Figure 9 View Figure 9 ). The pallial complex is narrow and elongated, 30 mm long on average. A nearly triangular kidney is located proximally in the lung cavity alongside the periaortic intestinal bend. The kidney is twice as long as wide and occupied 24% of the length of the lung.
The primary ureter runs along the rectal side of the kidney up to the top of the lung cavity; it then turns down along the rectum and forms the secondary ureter, which opens in the ureteric pore at the level of the upper third of the kidney. From this point on, the open secondary ureter is delimited by two ridges forming a ureteric groove that ends at the pneumostome. The ad-rectal ridge is less developed than the ab-rectal one.
The pericardium, located in the upper columellar side of the pallial system, is 2.4–5.4 mm long. It is continuous with the prominent pulmonary vein that runs parallel to the rectum and reaches the mantle collar. The pulmonary vein is 15.0– 24.4 mm long.
The afferent marginal vein branches out approximately from the distal third of the pulmonary vein, equalling about 41% of its length.
The studied material showed a moderate vascularization on the ad-rectal area between the rectum and the pulmonary vein, and between the pulmonary vein and the marginal afferent vein. A marginal vein of weak development branches out from the last portion of the pulmonary vein and runs along the mantle collar border.
The mantle collar includes a whitish spongy pallial gland and several indentations corresponding to the apertural teeth.
Reproductive system ( Figures 10 View Figure 10 , 11 View Figure 11 ). The ovotestis, embedded in the digestive gland, is composed of four to six groups of digitiform acini. The hermaphroditic duct is brown, markedly convoluted, and runs along the columellar side. The central portion of the duct is inflated to form the vesicula seminalis. The albumen gland is elongated, brownish orange, and lies against the anterior, concave surface of the digestive gland over the digestive pouch. The fertilization pouch–spermathecal complex is white, conspicuous and visible on the basal side of the albumen gland ( Figure 10C,D View Figure 10 ). The fertilization pouch–spermathecal complex is proximally swollen, while the distal part is composed of a blind sac.
The spermoviduct is formed by a hyaline whitish-cream oviducal portion (uterus) and a white and glandular prostate. The uterus ends at the free oviduct, while the prostate is continuous with the vas deferens. The latter is a tubule of constant diameter that emerges just above the bifurcation of the vagina to the free oviduct and the bursa copulatrix duct; this bifurcation is marked by a notorious constriction. The vas deferens runs attached to the vagina and penis surface; it passes through the retractor muscle and ends in the epiphallus–flagellum boundary. It is shorter than the sum of the length of the penis and the epiphallus. The penis retractor muscle is attached to the penis–epiphallus boundary.
The bursa copulatrix or gametolytic gland is a round sac, 1.6 mm in diameter. The bursa copulatrix duct is about 18.3 mm long; internally it has straight folds or lamellae.
The penial complex, 19.4–25.3 mm long, occupies a high proportion of the anterior portion of the visceral cavity. It is composed of the penis, epiphallus and flagellum ( Figure 11 View Figure 11 ). The penis, c. 7.8 mm long, is subcylindrical to club-shaped, with a slight proximal swelling 1.8–3.1 mm wide. The penial sheath is very short. Internally, the penis has a penial papilla or verge with a small accessory lobe about a third to half the size of the papilla; the papilla is continuous with the epiphallus ( Figure 11E,F View Figure 11 ). The inner wall of the penis has four or five longitudinal folds or pilasters that are prominent, undulated, and can be to some extent anastomosed. The pilasters do not extend underneath the papilla. The epiphallus 6.5–10.0 mm long is cylindrical, and its transition to the penis is not clearly marked by a constriction. Internally, it has five straight folds and has a proximal partition at the point where the folds join to form a minute hollow papilla. The epiphallus continues in a cylindrical tube running into the fleshy penial papilla. This tube has an internal sculpture of elevated and branched, anastomosed folds ( Figure 11E, F View Figure 11 ).
The vas deferens insertion demarcates the limit between epiphallus and flagellum. The flagellum, from 4.0 to 7.7 mm long, is cylindrical and has three straight folds that gradually merge to form one internal fold. It is as long as the epiphallus though markedly thinner.
The vagina is shorter than the penis, about 2.4 times as long as wide, and centrally swollen. The inner vaginal surface bore about 10 longitudinal, parallel lamellae with some anastomoses that do not give it a general reticulated aspect ( Figure 10E View Figure 10 ); two out of the seven dissected specimens showed some higher degree of reticulation ( Figure 10F View Figure 10 ). A genital atrium is almost absent, because the vagina and penis merge together at the genital pore.
Comparative shell morphometry
Principal component analysis on shell parameters of the five compared species yielded two principal components with eigenvalues>1 accounting for 84.4% of the total variance ( Table 2; Figure 12 View Figure 12 ). Principal component 1 (PC1), a size and shape axis, was positively correlated with the linear variables and the spiral angle, while it was negatively correlated with the major angle. PC2 positively correlated with the shell length and the major angle, and negatively correlated with the spiral angle. The scatter plot in Figure 11 View Figure 11 shows that P. weyrauchi sp. nov. mostly scored in the quadrant defined by negative values of PC1 and positive values of PC2, mainly because of its smaller general size and more acute shell (higher values of the major angle and lower values of the spiral angle and linear variables, except the shell length, which amply overlaps the range of other species; Table 3).
The remaining species were grouped at the intersection of the axes, though each one spread out towards a definite direction. While P. patagonicus from southern Buenos Aires province mainly scored on the quadrant defined by positive values of PC1 and negative values of PC2 because of its larger and more rounded shell, its sympatric species, P. rocae , scored towards positive values of both axes because of its slender and relatively large shell. Most scores of P. dentatus and P. multiplicatus parvus overlapped in intermediate values, but the former species tended to score in negative values of both components (small and slender shells) and the latter scored positively for PC1.
Multivariate discriminant analysis of the two forms inhabiting the Pampean Sierras in central Argentina, namely P. weyrauchi sp. nov. and P. multiplicatus parvus , yielded 100% correct classification, i.e. the discriminant scores of the two species did not overlap at all ( Figure 13 View Figure 13 ). Plagiodontes weyrauchi specimens scored towards positive values of the discriminant function because of its smaller size and more slen- der shell, whereas P. multiplicatus parvus scored towards negative values, correlating with the spiral angle and lineal measurements ( Table 4).
Bonferroni’s comparisons between all pairs of species showed that P. weyrauchi significantly differs from the remaining species in its shell width, last whorl length, aperture length, major aperture length, spiral and major angles, and by the proportions SW/SL, LWL/SL and AL/SL ( Table 3). Furthermore, the number of whorls partially overlaps only with P. rocae from the Sierra of Curamalal, Buenos Aires province.
Internal anatomy of similar species
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