Diversity, distribution, and evolutionary history of the Austral, Late Cretaceous to Eocene, gastropod Struthioptera (Stromboidea: Aporrhaidae)

JD Stilwell

Abstract

The prominently alate and sculptured marine gastropod, Struthioptera (Caenogastropoda: Stromboidea: Aporrhaidae) appeared in the New Zealand region at the latest during the early Cenomanian (early Late Cretaceous). Struthioptera campiveta n. sp., from the Marlborough region, is the first member and likely progenitor of the group, but no potential ancestor to Struthioptera has been recovered from Lower Cretaceous rocks. Concomitantly with the final separation of the Gondwana fragments in the latest Cretaceous, species-level diversity of Struthioptera climbed and the group diverged into at least four coeval species by this time: S. haastiana in the New Zealand region; S. novoseelandica in both New Zealand and Chatham Islands; S. pastorei in southern Argentina, Patagonia; and S. smiti in the Antarctic Peninsula region.? protuberatus from the Late Cretaceous of Patagonia may also belong here. The Cretaceous-Tertiary (K-T) boundary extinction crisis reduced the genus to a single representative, S. osiris, in the early Danian (late Early Paleocene) in New Zealand, and its probable descendant, S. camachoi, from the Middle-Late Eocene of Antarctic Peninsula. Shell size in Struthioptera increased markedly over the K-T boundary and the group became extinct in the Late Eocene, probably as a result of marked temperature changes near the Eocene/Oligocene boundary. Presented here is the first detailed review of Struthioptera since the first specimen was collected at Wangaloa, South Island, New Zealand, in late 1868 or early 1869. Species of Struthioptera are inferred to have been epifaunal and/or semi-infaunal deposit feeders and rather gregarious marine snails in sandy facies along the shallow shelf.

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