Title
Stratigraphic record of the Neogene globorotalid radiation (planktonic foraminiferida)
Related Titles
Series:
Smithsonian contributions to paleobiology, no. 58
By
Cifelli, Richard
Scott, George A. M.
Smithsonian Institution. Press
Type
Book
Material
Published material
Publication info
City of Washington, Smithsonian Institution Press, 1986
Notes
Distributed to depository libraries in microfiche.
The histories of lineages forming the Neogene globorotalid radiation in the planktonic foraminifera are reconstructed primarily from stratigraphic distributions. Data on major taxa are synthesized, with particular reference to the development of shell design, and related to biogeograpy and evolutionary strategies.The radiation was established about the base of the lower Miocene by three groups (Fohsella, Globorotalia zealandica lineage, and G. praescitula plexus), which probably arose from separate paragloborotalid lineages.Common trends (size increase, chamber compression, keel development, reduced wall relief) early in the radiation culminated in the evolution of disklike taxa which, since the middle Miocene, have been centered in the tropics. The later phase of the radiation (post middle Miocene) was marked by architectural diversification as spiroconical (e.g., G. margaritae), ventroconical (e.g., G. truncatulinoides), and globose (e.g., G. inflata) taxa arose. Architectural diversification may be linked with watermass differentiation in the late Neogene.Neogene designs have close counterparts in the earlier, but phyletically isolated, Paleogene and Cretaceous radiations. There are also resemblances in ontogenetic strategies and lineage histories. Common adaptations are suggested, but specific functional explanations have not been established.Periods of major redesign are recognized in most lineages and are not confined to speciation events. Examples of stasis in adult morphology occur particularly in taxa that have evolved compressed, keeled shells. Bifurcations in lineages are indistinctly represented by wide spectra of morphotypes. Within the radiation very rapid speciation events are conspicuously absent, although they possibly occurred at the origin of some lineages. The distinctly sluggish tempo of change may be due to large population sizes and their degree of intercommunication. Good examples of allopatric and parapatric speciation were not found, but the prevalence of polytypic taxa, often distributed in contiguous populations showing clinal variation, would favor the inception of parapatric speciation.
Subjects
Geology, Stratigraphic
,
Globorotalia, Fossil
,
Paleontology
,
Tertiary
BHL Collections
Unearthed! Smithsonian Libraries' Paleo Collection
Call Number
QE701 .S56 no. 58
Language
English
Identifiers
DOI:
https://doi.org/10.5479/si.00810266.58.1
LCCN:
https://lccn.loc.gov/84600360
OCLC:
11519073
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