Remarks on West Pacific Nummulitidae (Foraminifera)

Abstract

Living Nummulitidae achieve their highest diversity in the subtropical and tropical West Pacific. Although all house symbiotic microalgae, they avoid highly illuminated areas near the water surface, since their flat tests could be easily damaged by the hydrodynamic regime. The preference for calm water conditions extends their depth distribution down to the base of the photic zone. West Pacific Nummulitidae can be differentiated into ten species belonging to six genera according to an ecological species concept. The genus Operculina d'Orbigny is represented by three species. While O. discoidalis (d'Orbigny) prefers a fine-grained bottom under medium light conditions (10% surface intensity), O. ammonoides (Gronovius) prefers a coarser substrate and sometimes can be found on hard bottoms. Light dependence ranges from 1.5% to 68% surface intensity. Less illuminated coarse sands are inhabited by Operculina cf. O. complanata (Defrance), which is the dominant symbiont-bearing foraminifer between light intensities of 0.2% to 12% surface illumination. The genus Planostegina Banner and Hodgkinson demonstrates transitions to the genus Operculina in test form and surface, while the division into chamberlets is similar to Heterostegina. Planostegina operculinoides (Hofker) is distinguished by flat tests and delicate chamberlets. It lives on sandy bottoms restricted to light intensities between 0.45% and 26% surface illumination. The more robust Planstegina aff. P. operculinoides (Hofker) prefers light intensities between 0.4% and 2.7% surface illumination. Planoperculina heterosteginoides (Hofker) shows morphological transition to Operculina cf. O. complanata in developing incomplete septula. This species lives in low illuminated areas (0.3% to 2 .5% surface intensity) and prefers medium to fine-grained sands. Heterostegina depressa d'Orbigny spans a broad range in light intensities (2% to 70% surface illumination), and is protected against irradiation by thick tests and a cryptic life mode near the surface. Test construction enables life under strong hydrodynamic regimes. This species lives firmly attached to hard substrates, thus counteracting transportation by water movement. Nummulites venosus (Fichtel and Moll) differs from H. depressa in having undivided chambers.It lives exclusively on coarse sand and avoids high sediment movement, thus starting its distribution beneath the fair weather wave base. According to light intensities, the upper limit may be similar to O. ammonoides (80%), while the lower limit is 2.5% surface illumination. Operculinella cumingii (Carpenter) inhabits coarse to medium sand in deeper regions between 1.2% and 25% surface illumination. Tests of the cyclic, large-sized species Cycloclypeus carpenteri Brady are easily transported due to the thin, plate-like form. The upper distribution limit correlates with the storm wave base, restricting C. carpenteri to depths below 50 m. The lower distribution limit depends on light intensity and is located near the base of the photic zone (0.4% surface illumi...

Growth, chamber building rate and reproduction time of Palaeonummulites venosus (Foraminifera) under natural conditions

“…Palaeonummulites venosus (Fichtel and Moll) belongs to the group of symbiont-bearing larger benthic Foraminifera (LBF) (e.g., Hohenegger et al 2000 and references therein). These Foraminifera can be the main carbonate producers in reef moats (Yamanouchi 1998), lagoons (Ujiie and Ono 1995) and deeper slopes (Ujiie and Shioya 1980) in the surrounding of coral reefs (Langer et al 1997).…”

Morphological variations in Cycloclypeus carpenteri: Multiple embryos and multiple equatorial layers

“…This species is well adapted to live in deeper parts of the photic zone (Hohenegger et al, 2000). It has a large, circular and centrally umbonate test narrowed at the periphery (Loeblich and Tappan, 1988) (Figure 1.2-3; Appendix 1).…”

Evolution and Geological Significance of Larger Benthic Foraminifera

“…Modern species of Cycloclypeus are believed to live in deeper waters of 70-130m, down to the lower limit of the photic zone, crawling on firm substrates (Hottinger, 1983;Reiss and Hottinger, 1984;Hohenegger et al, 2000;Hohenegger and Yordanova, 2001;Yordanova and Hohenegger, 2002). They therefore tolerate lower light levels and temperatures than most other larger foraminifera (Cole, 1957).…”

“…The Baculogypsinoides individuals, with 3-4 strong spines, are similar to the genus Asterocyclina. They live on coral rubble and are extremely rare on sandy bottoms in Okinawa (Hohenegger, 2000;Hohenegger et al, 2000;Hohenegger and Yordanova, 2001;Yordanova and Hohenegger 2002) and the Spermonde Archipelago, Indonesia (Renema and Troelstra, 2001). Therefore, the homeomorph asterocyclinids with five to six rays might have lived on firm substrates in high energy environments, along with asterigerinids and amphisteginids, at depths of less than 30 m (Hallock, 1999;Ćosović et al, 2004).…”

“…involving a rapid increase in species diversity, shell size, and adult dimorphism, during the Paleocene-Eocene transition (Hottinger, 1998). Fossil Nummulites are known to have developed a large range of shapes induced by reproductive strategies (small sexual A-forms and large asexual B-forms, see Chapter 1) and by environmental factors (light intensity and hydrodynamic conditions), which significantly affect the size, shape and thickness of the tests (Hallock 1979(Hallock , 1981Hallock and Glenn, 1986;Hohenegger et al, 2000Hohenegger et al, , Ćosović et al, 2004. The hydrodynamic behaviour of Nummulites, which depends on their size, shape and density, is a fundamental parameter controlling their transport.…”