On the occurrence of Spinidelphinulopsis whaleni (Gastropoda) in the Late Triassic (early Norian) Cornwallis Limestone, Kuiu Island, southeastern Alaska (Alexander terrane) and its paleobiogeographic significance


Authors: Blodgett RB, Frýda J

Published in: Bulletin of Geosciences, volume 76, issue 4; pages: 235 - 242;

Keywords: Neritimorpha, Delphinulopsidae, paleobiogeography, accreted terranes, Triassic, Alaska,

Export to RIS



The gastropod Spinidelphinulopsis whaleni Blodgett, Frýda and Stanley, 2001, was originally described from late Carnian or early Norian strata on the Oregon side of Hells Canyon in the Wallowa terrane of the Pacific Northwest (Oregon, Idaho, and Washington). It is probably also present in early Norian strata at Green Butte, Wrangell Mountains (Wrangellia terrane) of southern Alaska. The common presence of this species and many other shared gastropod species has previously been cited as being evidence for close biogeographic linkage between the Wrangellia and Wallowa terranes. Quite dissimilar, coeval gastropod faunas are found in the in-board Alexander terrane of southeastern Alaska. New collections from early Norian strata on Kuiu Island, southeastern Alaska (Alexander terrane) show that S. whaleni is also present in this terrane as well, in association with an essentially totally differing gastropod fauna dominated by pleurotomaroids, trochoideans, and purpurinids. Explanation for the now known widespread distribution of this neritimorph species in a number of different terranes in eastern Panthalassa during Late Triassic times seems to be best attributed to it having a relatively long-lived planktonic larval stage, allowing it to be relatively well dispersed.