How to identify fossil molluscan communities associated to seagrass? An example from the Miocene of Banjung Ante, Java, Indonesia

Publication Type:Conference Paper
Year of Publication:2011
Authors:S. Reich, Wesselingh, F. P., Renema, W.
Conference Name:Molluscan Forum
Date Published:30/11/2011
Publisher:The Malacologist
Refereed Designation:Does Not Apply
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How to identify fossil molluscan communities associated to seagrass? An example from the Miocene of Banjung Ante, Java, Indonesia Sonja Reich1, Frank P. Wesselingh1, Willem Renema1 1Department of Geology, NCB Naturalis, Leiden, the Netherlands Email: Seagrass meadows are highly productive habitats which play an important role in sediment stabilization and nutrient cycling. They provide food and shelter for a diverse associated faunal community of vertebrates and invertebrates, such as molluscs. Seagrass meadows already played an important role in the past. They originated about 100 Ma ago and expanded geographically during the Miocene when also major diversifications in numerous marine taxa took place in the Indo-Malayan region, today’s centre of marine biodiversity. Due to their low preservation potential seagrasses are rare in the fossil record. Therefore the occurrence of ancient seagrass meadows has to be inferred from sedimentological and palaeontological data such as associated molluscan-foraminifer faunas. High abundances of small grazers such as Bittium and the occurrence of certain key taxa such as the neritid gastropod Smaragdia might provide indication for the former presence of seagrasses. Here we show a highly diverse and exceptional well preserved fossil assemblage from Banjung Ante (Yogyakarta, central south Java) as an example of a likely seagrass associated mollusc fauna. The fauna is of early Burdigalian (Early Miocene) age according to the associated larger benthic foraminifers. The molluscan assemblage is dominated by small to minute gastropods. All in all 4127 individuals of 163 species of bivalves and gastropods including Smaragdia were found. Based on the ecological composition the gastropods and bivalves were assigned to six feeding guilds. The percentage of each feeding guild is illustrated in terms of diversity and abundance. The difference between diversity and abundance data is remarkable: Small herbivorous gastropods are by far the most abundant group, but predatory carnivores are clearly the most diverse. The ecological pattern investigated shows striking similarities to another fossil seagrass associated mollusc fauna from East-Kalimantan (Beets, 1941) and a modern seagrass associated mollusc fauna from Spain (Rueda et al., 2009) while it differs from a number of communities from other habitats such as coral reef associated faunas (own observations) and estuarine communities (Lozouet & Plaziat, 2008). Further research will be carried out to investigate the possibility for the characterization of ancient seagrass habitats by the ecological composition of fossil molluscan communities.

Thu, 2011-11-03 15:39 -- sonja
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