Parachondria (Chondropomorus) pilsbryi ( Bartsch, 1946 )

Watters, G. Thomas, 2016, Review of the Hispaniolan Parachondria (Chondropomorus) complex (Gastropoda: Littorinoidea: Annulariidae), Zootaxa 4127 (2), pp. 245-275 : 267-268

Parachondria (Chondropomorus) pilsbryi ( Bartsch, 1946)

Figures 4 I–W, 6 A

Type material. Chondropoma (Chondropomorus) pilsbryi pilsbryi Bartsch, 1946 : NMNH 515241, holotype. Chondropoma (Chondropomorus) pilsbryi nonuni Bartsch, 1946 : NMNH 515243, holotype.

Type locality. Chondropoma (Chondropomorus) pilsbryi pilsbryi Bartsch, 1946 : “ Guayubin Rio Yaque del Norte, Monte Cristi Province, Dominican Republic.” Chondropoma (Chondropomorus) pilsbryi nonuni Bartsch, 1946 : “ Navarrete Station on the railway between Puerto Plata and Santiago, Santiago Province, Dominican Republic.” Navarrete is now called Bisonó and is located on the railroad that runs from Puerto Plata through Santiago to Bisonó some 25 km further west.

Type figured. Chondropoma (Chondropomorus) pilsbryi pilsbryi Bartsch, 1946 : Bartsch, 1946: pl. 1, fig. 6. Chondropoma (Chondropomorus) pilsbryi nonuni Bartsch, 1946 : Bartsch, 1946: pl. 1, fig. 7.

Chresonymy. Chondropoma (Chondropomorus) hemiotum “(Pfeiffer, 1852) ” Henderson & Bartsch, 1920: 61; Bartsch, 1946: 10–11, pl. 1, fig. 1 [non Pfeiffer, 1852].

Chondropoma (Chondropomorus) pilsbryi pilsbryi Bartsch, 1946: 13 –14, pl. 1, fig. 6; Ruhoff, 1973: 114; Watters, 2006: 408.

Chondropoma (Chondropomorus) pilsbryi nonuni Bartsch, 1946: 14 , pl. 1, fig. 7; Ruhoff, 1973: 104; Watters, 2006: 408 –409.

Parachondria (Parachondria) pilsbryi pilsbryi ( Bartsch, 1946) . Watters, 2006: 46, 408.

Parachondria (Parachondria) pilsbryi nonuni ( Bartsch, 1946) . Watters, 2006: 46, 408–409.

Distribution and habitat. This species occurs in the western half of the Cibao Valley between the Cordillera Central and the Cordillera Septentrional on low limestone ridges and foothills bounding the Río Yaque del Norte valley. It continues around the western end of the Cordillera Septentrional along the coast east to Puerto Plata. These coastal areas include isolated low hills having populations that may prove to be distinct. In leaf litter and around limestone blocks in submesic scrub. Locally abundant.

Material examined (578 specimens). Dominican Republic. UF 216472(3), 5 km S of Los Quemados, Santiago Rodriguez Province; UF 216759(88), 50 m, 1 km S of Guayabin, Monte Cristi Province; UF 216764(27), 190 m, 1 km ESE of Guayabin, Monte Cristi Province; UF 216750(138), 230 m, 2 km N of Sabana Cruz, Monte Cristi Province; UF 216765(8), 9 km S of Sabana Cruz, Monte Cristi Province; UF 216763(27), 190 m, 11 km W of Agua de la Palma, Monte Cristi Province; UF 216758(125), 270 m, 7 km E of San Ignacio de Sabaneta, Santiago Rodriquez Province; UF 216762(16), 220 m, 17 km E of San Ignacio de Sabaneta, Santiago Rodriquez Province; UF 216755(47), Las Lagunas, Espaillat Province. UF 216756(19), 60 m, 6 km WNW of Luperón, Puerto Plata Province; UF 216757(23), 30 m, 4 km NW of Luperón, Puerto Plata Province; UF 158947(14), Copey, Monte Cristi Province; UF 230908 (2), road to Punta Rucia, Monte Cristi Province; UF 18949(2), UF 158952(28), UF 184442(11), Puerto Plata, Puerto Plata Province.

Redescription. Shell thin, usually opaque but some nearly translucent, high-spired, elongate conic. Maximum adult size: 18.1 mm, decollate. Minimum adult size: 10.7 mm, decollate. Adult shell usually decollated, protoconch of 1.5 minute, white or tan, smooth whorls, demarcation between protoconch and teleoconch not well-defined.

Teleoconch of 4–4.5 whorls remaining in decollated shells. Axial sculpture of final whorl of numerous (ca. 80– 120), microscopic, narrowly spaced threads; these may be nearly obsolete and apparent only as tiny beads on spiral sculpture. Shell usually with regularly spaced growth stoppage marks, with 5–10 axial threads in each group. Spiral sculpture of final whorl ca. 30–50 very fine threads, nearly obsolete on base. Overall sculpture not distinct, very polished, microscopically pitted rather than fenestrate. Umbilicus bounded by one low cord, smooth within. Suture not channeled. Tufts composed of 1–3 axial threads forming irregularly spaced, nearly obsolete, minute beads. Aperture teardrop-shaped, lip single, not expanded. Lip clearly detached from previous whorl for ¼ turn. Posterior angle forms sharp crest but auricle lacking. Color pattern complex and very variable. Base color white, tan, yellowish, or dark brown. Axial color patterns at leading edge of growth lines composed of dark dots, zig-zag lines, or combinations of light and dark patches. There is always some indication of more or less continuous dark band on base. Tufts white. Operculum paucispiral with thin granular deposit.

Variation in specimens. The variation in color patterns within a single population exceeds that of any other species in the complex, from nearly uniformly dark brown to uniformly white. The strength of the axial sculpture is always weak but may be nearly absent in some specimens. Specimens from Cabo Isabela are more polished than specimens from other populations. That population occupies a very restricted range between Luperón and La Isabela on a series of low, isolated hills formed from Pliocene/Pleistocene reefs on the north shore. Phylogenetic work may reveal these to be a distinct taxon.

Comparison with other species. The combination of a highly polished surface and nearly obsolete axial sculpture is unique in this group. It is most similar to P. olssoni , which differs in having more prominent sutural cusps, a deeply channeled suture, and in having prominent, interrupted, brown spiral bands; the latter characteristic is rare in P. pilsbryi .

Remarks. This is the species referred to by Bartsch (1946) as Chondropoma hemiotum Pfeiffer, 1852 . His species does not match the description or figures of Pfeiffer’s species, which may represent an earlier name for P. samanicolus ( Bartsch, 1946) (see under P. samanicolus ).

The subspecies C. pilsbryi nonuni was described by Bartsch (1946) for specimens having better developed sutural elements and a more cylindrical shape, but these are minor differences that vary within populations.

Original description. Chondropoma (Chondropomorus) pilsbryi pilsbryi Bartsch, 1946 : see Bartsch, 1946: 13–14. Chondropoma (Chondropomorus) pilsbryi nonuni Bartsch, 1946 : see Bartsch, 1946: 14.

Etymology. Chondropoma (Chondropomorus) pilsbryi pilsbryi Bartsch, 1946 : Henry Augustus Pilsbry (1862– 1957), American conchologist, Academy of Natural Sciences, Philadelphia. Chondropoma (Chondropomorus) pilsbryi nonuni Bartsch, 1946 : unknown.

Figures

FIGURE 4. A – H. Parachondria (Chondropomorus) olssoni (Pilsbry, 1933). A, B. ANSP 160978 a, holotype, 14.5 mm. C, D. UF 119142, 14.4 mm. E. UF 158947, 14.7 mm. F. GTW 6834 a, 15.5 mm. G. GTW 6834 a, detail of spire. H. GTW 6834 a, detail of suture.