Parachondria (Chondropomorus) olssoni Pilsbry 1933

Parachondria (Chondropomorus) olssoni (Pilsbry, 1933)

Figures 4 A–H, 5 B

Type material. ANSP 160978 a, holotype (as lectotype in Richardson et al., 1991); ANSP 160868 (4), paratypes; ANSP 373757(3), paratypes (all as paralectotypes in Richardson et al., 1991), ANSP 160978 (1), paratype; AMNH 95461(5), paratypes.

Type locality. “ Cerro Monte Cristi, Santo Domingo.”

Type figured. Pilsbry, 1933: pl. 6, figs. 1–4.

Chresonymy. Chondropoma olssoni Pilsbry, 1933: 125, pl. 6, figs. 1–4; Baker, 1964: 170; Watters, 2006: 385.

Chondropoma (Chondropomorus) olssoni Pilsbry, 1933. Bartsch, 1946: 12, pl. 1, fig. 4.

Parachondria (Parachondria) olssoni (Pilsbry, 1933). Watters, 2006: 46, 385.

Distribution and habitat. This species appears to be endemic to the isolated Sierra Monte Cristi and the surrounding area including the famous El Morro formation. Specimens have been found under tall grass and on wooded slopes. Locally common.

Material examined (116 specimens). Dominican Republic. GTW 6834a(1), UF 119140(8), El Morro, Monte Cristi Province; UF 119140(8), UF 119141(7), UF 158943(7), Monte Cristi, Monte Cristi Province; UF 216699(48), Sierra Monte Cristi, 3 km NE of Monte Cristi, Monte Cristi Province; UF 216700(4), UF 216702(9), UF 216703(1), Sierra Monte Cristi, 5 km NE of Monte Cristi, Monte Cristi Province; UF 119142(31), hill 4 km S of Monte Cristi, Monte Cristi Province.

Redescription. Shell thin, opaque, high-spired, elongate conic. Maximum adult size: 14.6 mm, decollate. Minimum adult size: 9.8 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 4.5 whorls remaining in decollated shells. Axial sculpture of final whorl of numerous (ca. 110), equally spaced threads separated by intervals equal to their width. Spiral sculpture of final whorl ca. 40 equally spaced threads separated by intervals equal to their width. Overall sculpture finely fenestrate. Umbilicus bounded by one low cord, smooth within. Suture deeply channeled, where every other axial thread forms elongate denticle. Aperture teardrop-shaped, lip single, not expanded. Lip clearly detached from previous whorl for almost ½ turn. Posterior angle forms sharp crest but auricle lacking. Color pattern consistent. Base color white, gray, or tan with 5–8 broken, spiral brown bands, often aligned as axial spots. Umbilicus and tufts white. Operculum paucispiral with thin granular deposit.

Variation in specimens. This is a very consistent species, varying primarily in the degree to which the spiral bands are continuous or broken.

Comparison with other species. This species is most similar to the adjacent P. pilsbryi, but differs in the more prominent sutural elements and channeled suture. The banded color pattern of P. olssoni is rarely seen in P. pilsbryi. Etymology. Axel Adolph Olsson (1890–1977), American paleontologist, conchologist.