Turritella capistrata, DeVries, 2019

DeVries, Thomas J., 2019, Early Paleogene brackish-water molluscs from the Caballas Formation of the East Pisco Basin (Southern Peru), Journal of Natural History 53 (25), pp. 1533-1584 : 1568-1569

Turritella capistrata sp. nov.

( Figure 5 (f), 5(g))

Diagnosis

Whorls imbricate, with three strong primary spiral cords, nearly evenly spaced between sutures. Lateral growth line prosocline with anterior inflexion only.

Description

Estimated shell length to 25 mm, pleural angle about 19°. Protoconch unknown. Spire with about 10 whorls. Earliest preserved whorls straight-sided to concave, imbricate; spiral formula C1A1 and subsequently D2C1B2A1. Later whorls imbricate with strong primary spirals and insertion of secondary spirals; successive formulae D2C 1t 3B2s3A1r3 and D2C 1t 3B2s3s4A1r3r4; primary spiral ‘ D ’ variably exposed, primary spiral ‘ B ’ sometimes weaker than primary spirals ‘ A ’ and ‘ C ’. Spacing formula C27B46A77 (n = 4). Lateral growth line orthocline to slightly prosocline, inflected anteriorly only. Lateral sinus moderately deep, apex situated close to spiral ‘ B ’. Base convex with at least two spirals, basal growth line probably radial, but base mostly obscured. Allmon formula 2?-4-S-B-OR.

Remarks

Specimens of Turritella capistrata sp. nov. most closely resemble those of T. desolata Olsson, 1944 , a late Maastrichtian species from the Tortuga Formation in the Sechura Basin of northern Peru ( Olsson 1944; Jaillard et al. 2005) and the Upper Cretaceous Chonta Formation of eastern Peru ( Singewald 1926; Pilsbry 1944; CGS Consultores Associados S.A 1997; Leon et al. 1997). The Tortuga Formation species has a smaller pleural angle (12°; n = 2) and is larger (> 50 mm; Olsson 1944) than the Caballas Formation species, but the spiral sculpture is identical.

Etymology

‘ Capistrata ’, Latin adjective for ‘ bound ’, referencing the seeming binding of each capstan-like whorl with coils of rope.

Material

UWBM 107601 , holotype, B8770 (type locality), L (14.4), W 8.6 ; remainder are paratypes: UWBM 107603 , B8770, L 24.0, W 7.1 ; UWBM 107604 , B8770, L (18.5), W 10.4 ; MUSM INV 259 , B8772, L (16.3), W (7.5) ; MUSM INV 260 , B8770, L (21.5), W (8.3)

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Occurrence

Lower Paleogene, Cuenca Member, Caballas Formation, East Pisco Basin, southern Peru.

Figures

Figure 5. Gastropods from the Caballas Formation. (a–e) Caballasea segmentata gen. nov., sp. nov. B8769. (a) UWBM 107607, paratype, L 12.4 mm, apertural view. (b) UWBM 107607, abapertural view. (c) UWBM 107606, holotype, L 12.6 mm, abapertural view. (d) MUSM INV 262, paratype, L 8.3 mm, oblique view of parietal callus and columella. (e) UWBM 107608, paratype, L 15.3 mm, abapertural view. (f, g) Turritella capistrata sp. nov. (f) MUSM INV 259, paratype, B8772, L 16.3 mm, lateral view. (g) UWBM 107601, holotype, B8770, L 14.4 mm, apertural view. (h) Turritella saposa Olsson, 1944, UWBM 107602, B8770, L 15.5 mm. (i) Cristispira caballasensis sp. nov., UWBM 107605, holotype, B8769, L 5.1 mm, fragment. (j, k, m, n) Rhombopsis longinquus sp. nov. (j) UWBM 107630, holotype, B8772, L 18.3 mm, apertural view, outer lip missing. (k) MUSM INV 269, paratype, B8769, L 19.9 mm, abapertural view. (m) UWBM 107631, paratype, B8772, L 22.5 mm, abapertural view. (n) UWBM 107632, paratype, B8769, L 16.4 mm, lateral view of spire and columella. (l, o–q) Tristeirostoma saxaquadrata sp. nov. B8771. (l) UWBM 107636, paratype, L 10.0 mm, spire. (o) UWBM 107,635, holotype, L 7.6 mm, abapertural view. (p) UWBM 107635, lateral view of columella. (q) UWBM 107635, apertural/lateral view.