Radiation of Cenozoic Planktonic Foraminifera

Abstract

The general aspects of planktonic foraminiferal radiation during the Cenozoic are shown by the distributional patterns of several morphotypic groups. There were two major radiations, one occurring during the Paleogene, the other during the Neogene. The radiations followed severe reductions in diversity which occurred at the close of the Cretaceous and again during the mid-Tertiary. Distributional patterns are iterative, and the Neogene radiation is essentially a repetition of what occurred during the Paleogene. According to the present interpretation, the ilerative patterns reflect major changes in the dynamic structure of surface waters. By analogy with the distribution of the modern fauna, it is suggested that thermal barriers were degraded during times of reduction and the oceans were uniformly cool. During the radiations thermal gradients were restored and the structure of the surface waters was essentially as it is today.

Molecular systematics, historical ecology, and phylogeography of Halimeda (Bryopsidales)

“…Examples of convergence among extant taxa already illustrate such repetition. Similar patterns have been recovered among taxa with an extensive fossil record such as ammonites (Newell, 1967) and Foraminifera (Cifelli, 1969).…”

“…Many Late Cretaceous and Early Tertiary fossils show similarity to extant groups of species Morellet, 1922, 1941;Schlagintweit and Ebli, 1998) suggesting that the extant diversity consists of living fossils. Alternatively, similar phenotypes may have appeared through iterative evolution (Cifelli, 1969;Newell, 1967).…”

Evolution of the Cretaceous calcareous nannofossil genus Eiffellithus and its biostratigraphic significance

“…This diversification may be related to changes in environmental determinants such as sealevel, surface water temperatures, nutrient availability, and water stratification. Such events are seen in several microfossil taxa through time (Aubry, 1988;Cifelli, 1969) and highlights the need for further discussion and collaboration on such topics within the microfossil community. This type of community study, however, requires a better understanding of nannofossil taxonomy, morphology and diversity through time.…”

Morphological variability of Globorotalia menardii (planktonic foraminifera) in two DSDP cores from the Caribbean Sea and the Eastern Equatorial Pacific

“…Although the adaptive advantage of having a keel is poorly understood, the development of a peripheral keel has been considered repeatedly a character useful in the study of evolution in the lineages of several planktic foraminifera (CIFELLI, 1969;BOLLI, 1986;ARNOLD et alii, 1995;PARKER et alii, 1999). There are several ways to quantify geometric changes in the keel region: One is the investigation of the degree of curvature (bending, measured as the radius of the tangent circle) as one moves along the periphery of the keel.…”