Diversity and Paleoecology of Miocene Coral-Associated Mollusks From East Kalimantan (Indonesia)

Abstract

This study is a preliminary assessment of an extremely diverse Tortonian (late Miocene) mollusk assemblage from a coral carpet environment preserved at Bontang (East Kalimantan, Indonesia). Even though coral-associated aragonitic faunas are rarely well preserved, the composition of the assemblage described here can be used to address the following questions: (1) How do the mollusk assemblages in coral habitats differ from other habitats, and (2) What is the effect of sampling on estimates of taxon richness? The mollusk assemblage is dominated by predatory snails and includes typical modern coralassociated taxa such as the gastropod Coralliophila and the bivalve Tridacna. Our investigation implies that adequate documentation of Cenozoic mollusk diversity in the Indo-Pacific is even more challenging than previously expected as very large samples are required to capture species richness. Further assessments of fossil faunas from coral-dominated habitats will be required to provide insight to development of Indo-Pacific biodiversity through time.

Old Data for Old Questions: What Can the Historical Collections Really Tell Us About the Neogene Origins of Reef-Coral Diversity in the Coral Triangle?

“…So for taxonomic use, the collections might be adequate to develop taxonomic frameworks, but they are not suitable on their own for studies of diversity or ecology. For this work, additional ecologically sampled collections are required (Bromfield and Pandolfi 2011;Novak et al 2013;Kusworo et al 2015;Santodomingo et al 2015).…”

Fossils reveal a high diversity of the staghorn coral generaAcroporaandIsopora(Scleractinia: Acroporidae) in the Neogene of Indonesia

“…These habitats were dominated by branching colonies of the genera Dictyaraea , Seriatopora , Alveopora , Goniopora and Porites , and were the main habitat of Acropora species within the aspera group. Coral carpets usually co‐occur with seagrass environments (Kusworo et al ., ), and are interpreted as developing in shallow lagoonal palaeonvironments. Thus, it seems that species in the aspera group occupied a similar environment to one of those currently occupied (Wallace, ).…”

“…Other coral species of this locality include Antillia constricta , Pavona decussata , Porites nigrescens and Goniopora planulata (Gerth, ). Similar mixed mollusc–coral faunas of Miocene age in East Kalimantan have been interpreted as coral carpets that developed in sheltered habitats (Kusworo et al ., ). This suggests that A. grandis occupied a similar habitat in the Miocene as it does on modern reefs.…”

“…Typical coral‐associated molluscs were abundant among the accompanying fauna, such as Tridacna shells of about 20 cm length and the corallivorous Coralliophilla . Preservation of original aragonite in both corals and molluscs was observed (Kusworo et al ., ).…”

Paleoecological Significance of Stable Isotope Ratios in Miocene Tropical Shallow Marine Habitats (Indonesia)

“…Those sediments are covered by nonfossiliferous clay and fine sandstone beds likely representing the lowest deposits of a fluvial series. The locality is described in detail by Kusworo et al (2015). The shells used in this study were collected from patches of branching corals found on a bedding plane of marine silty clay (hand-collected sample SR45) and a bulk sample taken from the same bed (sample SR50).…”