Paleontology of the Early Pliocene Kairuku Limestone of Yule Island, Papua New Guinea - Part 1: Introduction, Gastropoda and Scaphopoda

 

Authors: Kiel S, Espi JO, Tai L, Zuschin M, Hautmann M

Published in: Bulletin of Geosciences, volume 100, issue 3; pages: 271 - 318; Received 30 May 2025; Accepted in revised form 29 October 2025; Online 21 December 2025

Keywords: Coral Triangle, biodiversity hotspot, Neogene, Mollusca, taxonomy,

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Abstract

We report 79 species of gastropods and five species of scaphopods from the Early Pliocene Kairuku Limestone on Yule Island, Papua New Guinea. All scaphopods are described in open nomenclature. The gastropod fauna comprises 39 families, with 40 species identified to species level, some tentatively (using ’aff.’). Of these, 30 are extant, three were first reported from the Miocene, and seven from the Pliocene. Among the extant taxa, seven range back to the Miocene and 21 to the Pliocene. Four species are here documented for the first time in the fossil record: Nerita costata Gmelin, 1791, Ministrombus aff. caledonicus Maxwell, 2022, Labiostrombus aff. epidromis (Linnaeus, 1758), and Aliculastrum aff. debile (Pease, 1860). The architectonicid Stellaxis nitens (Noetling, 1901) is identified as the geologically youngest member of this otherwise predominantly Eocene genus. Many species from the Kairuku Limestone had wide geographic distributions within the Indo-West Pacific region during the Pliocene. This suggests that any biogeographic separation between northern and southern sectors of the Coral Triangle biodiversity hotspot, inferred for the Late Miocene, had largely diminished by Early Pliocene time.