The oldest known cyclophoroidean land snails (Caenogastropoda) from Asia

Abstract

The earliest Miocene (Aquitanian, 23–21 Ma) Hang Mon Formation at Hang Mon in Northern Vietnam has yielded a rich assemblage of terrestrial gastropods. Four species from this assemblage belong to the land caenogastropod superfamily Cyclophoroidea. Three of these are assigned to genera with Recent representatives in Southeast Asia and are described as new species: Cyclophorus hangmonensis Raheem & Schneider sp. nov. (Cyclophoridae: Cyclophorini), Alycaeus sonlaensis Raheem & Schneider sp. nov. (Cyclophoridae: Alycaeinae) and Tortulosa naggsi Raheem & Schneider sp. nov (Pupinidae: Pupinellinae). These fossil species represent the earliest records for their genera and are thus of great value for calibrating molecular phylogenies of the Cyclophoroidea. The fourth species is represented only by poorly preserved fragments and is retained in open nomenclature in the Cyclophoridae. While extant Cyclophoroidea have their greatest diversity in Tropical Asia, the oldest fossils described to date from the region are from the Late Pleistocene. The fossils from Hang Mon predate these by more than 20 million years and are also globally among the earliest cyclophoroideans recorded from the area of the present-day forested Tropics. Cyclophoroidea older than the Miocene are only known from Europe. Given that Recent Cyclophoridae and Pupinidae are typically associated with tropical forests, it seems likely that the Hang Mon fossils were also tropical forest taxa and that suitable habitat was present in the general vicinity of Hang Mon in the earliest Miocene.

http://zoobank.org/urn:lsid:zoobank.org:pub:B0C2C715-1184-4930-BD94-21ED1E9281B4

Keywords:

• Cyclophorus
• Alycaeus
• Tortulosa
• early Miocene
• Vietnam
• palaeobiogeography

Acknowledgements

We would like to thank the following people: N. V. Hung, D. D. Quang and P. D. Pha for support in Vietnam; H. Taylor for imaging the fossils; M. Biszczuk for preparing the map of Hang Mon; B. Páll-Gergely for generously sharing his work on the taxonomy of the Vietnamese Alycaeinae, and providing images; K. and P. von Oheimb for supplying data on extant Vietnamese Cyclophorus; E. Gittenberger, M. Harzhauser, D. Kadolsky, F. Naggs, M. Pickford, G. Rosenberg, R. Salvador and E. Zallot for information on fossil taxa; J. Ablett (NHM), R. Preece (UMZC) and T. Schiøtte (Zoological Museum, Natural History Museum of Denmark, University of Copenhagen) for assistance with locating historical material; Ralf Britz for guidance on nomenclatural issues; J. D. Taylor for sharing with us his expertise on shell microstructure; D. Reid and D. Gower for commenting on early drafts of this paper; and T. Neubauer and an anonymous reviewer for reviewing the manuscript. All fieldwork was funded by Deutsche Forschungsgemeinschaft grant numbers BO 1550/11-1 & 2. This paper contributes to CNRS project GDRI 0849 PalBioDivASE.

Supplemental data

Supplemental material can be accessed online at: https://doi.org/10.1080/14772019.2017.1388298

Additional information

Funding

Deutsche Forschungsgemeinschaft [BO 1550/11-1 & 2].