Trypanocochlea cerithioides ( Koken, 1896 )

Nützel, Alexander & Karapunar, Baran, 2023, On Triassic Murchisonia-like gastropods-surviving the end-Permian extinction to become extinct in the Late Triassic, Acta Palaeontologica Polonica 68 (3), pp. 539-559 : 548

Trypanocochlea cerithioides ( Koken, 1896)

Fig. 6.

1896 Verania cerithioides Koken ; Koken 1896: 86, text-fig. 11.

1897 Verania cerithioides Koken ; Koken 1897: 105, text-fig. 29.

Material.— Lectotype, herein designated, SNSB-BSPG 1878 XI B 478 (original of Koken 1896: text-fig. 11; original of Koken 1897: text-fig. 29), Carnian (Upper Triassic), Röthelstein, Aussee, Austria. NHMW 1858/0047/0088, SNSB-BSPG 2011 XXXIX 78d, Carnian (Upper Triassic), Feuerkogel, Austria.

Description.—Shell high-spired, apical angle ca. 45°; type specimen consists of ca. 8 whorls, 7.8 mm high, 3.4 wide; earliest preserved whorls rounded, smooth, developing an angulation low on whorl face after one-two whorls; whorl face strongly angulated slightly below middle of whorl face; selenizone broad, situated on angulation, forming periphery; selenizone forms late (after the second preserved whorl), ornamented with pronounced node-forming lunulae, and a median spiral cord; lunulae closely spaced in early whorls, widely spaced in later whorls; selenizone bordered by outward bending shell forming sharp edges (spiral cords); whorl face steeply sloping above selenizone, ornamented with strengthened growth lines and spiral thread in subsutural zone; whorl face below selenizone sharply inclined adaxially; transition from whorl face to conical, convex base demarcated by spiral cord, accompanied by one or few spiral threads; aperture trapezoidal; inner lip convex with about 12 spiral lirae (folds).

Remarks.— Trypanocochlea cerithioides , type species of Trypanocochlea , is a murchisonimorph gastropod with a strongly ornamented, convex selenizone. Its inner lip has spiral lirae (folds) unlike any other members of Goniasmatidae . A middle Permian representative of Trypanocochlea , has been reported by Nützel and Nakazawa (2012) but that species seemingly lacks folds on the inner lip (maybe due to preservation). Similar gastropods (also lacking folds on the inner lip) have also been reported from the Pennsylvanian/lower Permian of the USA: Taosia crenulata ( Girty, 1939) ( Kues 1991, 2004a, b). Taosia crenulata differs much from the type species of Taosia , and at first glance this late Paleozoic species resembles Trypanocochlea . However, while the selenizone of Taosia crenulata is situated on upper whorl face above the nodular periphery, the selenizone of Trypanocochlea cerithioides is situated on the angular periphery and the nodes are formed within the selenizone. Cheilotomona subgranulata (Klipstein, 1844) from the St. Cassian Formation develops similar nodular selenizone on whorl periphery, but species of Cheilotomona lack the folds on inner lip. The only other report of Trypanocochlea (an unnamed species) is from the?upper Norian/Rhaetian (Upper Triassic) of Peru by Haas (1953), who reported absence of folds in the Peruvian species. Due to the unclear age if this probably last occurrence of Trypanocochlea , the exact timing of the exticntion of this genus is unknown.

Stratigraphic and geographic range.—Known from the type locality area only, see above.