Neogene crinoids of southeast Asia: preservation, systematics and significance

Abstract

Donovan, S.K. & Helwerda, R.A., August 2016. Neogene crinoids of southeast Asia: preservation, systematics and significance. Alcheringa 41, xxx–xxx. ISSN 0311-5518.

The Cenozoic record of fossil crinoids is poor. In part, this is because the stalked taxa have moved into deep water (>100–150 m water depth) since the Cretaceous, but also results from the propensity for the crinoid endoskeleton to disarticulate soon after death. Despite this, we report two new, small crinoid faunas of moderate diversity from the Pliocene of East Kalimantan and the Philippines. Included taxa are columnals of the isocrinid Metacrinus? sp.; a bourgueticrinid cup and columnal, Democrinus? sp.; and cirral and brachial ossicles (isocrinids and comatulids). The preservation of these Pliocene crinoids is not conducive to classification to the level of species, although some taxa are easier to determine than others, but the precise reason for this dearth of complete specimens remains uncertain. Because of our knowledge of extant crinoids, this Cenozoic ‘gap’ has been poorly appreciated. Rather than denigrating the Pliocene crinoids documented herein for being fragmentary and difficult to accurately determine, we instead report them as a rare set of data points, filling, in part, the Cenozoic ‘gap’.

Stephen K. Donovan [[email protected]] and Renate Helwerda [[email protected]], Naturalis Biodiversity Center, Postbus 9517, 2300 RA Leiden, The Netherlands. Received 03.05.2016; revised 16.06.2016; accepted 21.6.2016.

Key words:

• East Kalimantan
• Philippines
• Pliocene
• Metacrinus
• Democrinus
• deep-water palaeoenvironments

Acknowledgements

We thank Mr Arie W. Janssen and Dr Willem Renema (both Naturalis Biodiversity Center, Leiden) for providing access to the collections and bulk samples upon which this paper is based. Constructive review comments by Drs Tatsuo Oji (Nagoya University Museum, Japan) and Mariusz A. Salamon (University of Silesia, Poland) are gratefully acknowledged.