Mexistrophia reticulata Thompson, 2011

Original Description

"Mexistrophia reticulata new species

(Figures 1-6,20, 22,27,28,Table 1)

Diagnosis: Pupiform shell, moderately robust, about 9-13 mm long. Conspicuous white peristome lacking noticeable callus reinforcing it internally. Sculpture consisting of thread-riblets, with upper ends that weakly crenulate the suture.  Spermathecal duct with long appendix.

Description: Shell (Figures 1-6). Shell pupiform. Spire cylindrical, relativelv slender, with low domed-­shaped apex. Shell wall opaque.  Ground color light brown mottled with lighter irregular-shaped spots and streaks that form reticulated pattern. White streaks tend most conspicuous on upper ends of ribs. Peristome and adjacent interior of aperture white. Deeper within, inner wall and axis rust-colored. Shell 10.5-13.2 mm long, 3.9-4.4 mm wide, and 0.31-0.38 times as wide as long. Shell contains 8.0-9.2 whorls separated by weakly impressed suture. Protoconch consisting of two smooth whorls slightly elevated above following whorls.  Follow­ing whorls sculptured with numerous oblique thread-­riblets strongest on apical whorl, but nearly equally developed on spire. Riblets strongest below suture and weakly crenulate suture. Umbilicus imperforate or narrowly rimate. Thick  peristome weakly reflected and discontinuous across parietal wall, where it is replaced by thin glaze. Aperture ovate, slightly higher than wide, 0.28-0.33 times shell length, and 0.67-0.80 times shell width.  Aperture slightly prosocline in lateral profile (Figure 5). Axis conspicuously enlarged in apical whorls. Cylindric part of shell axis slightly sinuous, much narrower, and narrowly perforate or solid by last whorl (Figure 6). (Measurements based on the holotype and twelve paratypes are given in Table 1.)

Anatomy: Reproductive anatomy (Figures 20-22) (Five specimens examined (UF 211129): Genital atrium (atr) moderately long and capacious. Right ocular retrac­tor a narrow slip of muscle that passes mesad to lower genitalia, attaching to vagina in conjunction with vaginal retractor muscle. Stout penis (pen) bulbous, consisting of two nearly equal sections. Distal section forming glo­bose, blind diverticulum (div). Short penis retractor muscle (prm) originating on inner wall of lung and inserting on end of diverticulum. Epiphallus (epi) enter­ing middle of penis at base of diverticulum.  Epiphallus moderately stout at union with penis, but gradually grading into very long vas deferens.  Epiphallus lined inter­nally with simple longitudinal columns.  Spermatheca (spr) large and elliptical, resting against dorsal side of oviduct at base of albumen gland. Spermathecal duct (spd) stout, moderately long, enlarged at base where it is muscular and weakly convoluted. Duct bearing very long appendix (app) about as long as spermathecal duct.  End of appendix extending to upper end or albumen gland. Spermathecal duct uniting with free oviduct (fovi) to form short but distinct vagina (vag).  Free oviduct relatively stout and slightly longer than vagina. Heavy slip of muscle that is a branch of right pedal retractor inserting on vagina to form vaginal retractor muscle (vrm) (Figures 21-22).

Radula (Figures 27-28). Two specimens examined (UF 445301). Radular formula 14-1-14.  Transverse tooth rows nearly flat, not curving upward at ends. Transition from lateral teeth to marginal teeth not clearly differen­tiated morphologically. Eight lateral teeth and 6 marginal teeth present in each half-row. Lateral teeth rising slightly, and marginal teeth becoming nearly horizontal. Central tooth trapezoidal with indented dorsal edge, 18 mm wide and 20 mm high . Central tooth with large lanceolate mesocone, 15 mm long, extending to base of tooth. Mesocone flanked on each side by short acuminate ectocone. Lateral teeth with long, slender mesocone overlaping tooth below, and small ectocone. Marginal teeth with long mesocone and small ectocone.

Type Locality: A talus slope 1.0 km east of Pinal de Amoles, Querétaro State, Mexico, 21.15°N, 99.64°W, 2150 m alt.

Type Material: Holotype: UF 211128, collected 25 July, 1983 by Fred G. Thompson and Elizabeth L. Mihalcik;  Paratypes: UF 435013 (30), CN MO 3379 (5), all from type locality.

Other Material Examined:  UF 211129; type locality. Specimens preserved in 75% ETOH.

Habitat: The dominant vegetation in the area con­sists of pine forests with scattered small oak trees (Quercus sp.), Snails were found among grasses, mosses and sedum growing among limestone cobbles.

Distribution: Querétaro State, Mexico (known only from the type locality.)

Remarks:  For meristic comparisons with the other species see Mexistrophia inexpectata  new species below.

Etymology: The species name reticulata (Latin) alludes to the reticulated color pattern of the shell.

Table 1.  Mexistrophia reticulata new species. Measurements in mm of the holotype  (UF 211128) and 12 paratypes (UF 435013) selected to show variation.  SL = standard length, SW = standard width, ApH = aperture height; ApW = aperture width, Wh = Whorls.

                         SL       SW      ApH    ApW        Wh      SW/SL   ApH/SL   ApW/SW

Holotype         11.0     3.9       3.6       3.0       8.9       0.35        0.33        0.77


min                  10.5     3.9       3.2       2.8       8.0       0.31        0.28        0.67

max                 13.2     4.4       3.8       3.2       9.2       0.38        0.33        0.80

avg                  11.55   4.04     3.55     2.98     8.65     0.35        0.31        0.74"

(Thompson, 2011:183-185)

STD                 0.88     0.14     0.19     0.17     0.41     0.02        0.02         0.03

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