On the demise of the early Paleogene Morozovella velascoensis lineage; terminal progenesis in the planktonic Foraminifera

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doi: 10.1669/0883-1351(2001)016<0507:OTDOTE>2.0.CO;2
Author(s): Kelly, D. Clay; Bralower, Timothy J.; Zachos, James C.
Author Affiliation(s): Primary:
Woods Hole Oceanographic Institution, Department of Geology and Geophysics, Woods Hole, MA, United States
University of North Carolina at Chapel Hill, United States
University of California at Santa Cruz, United States
Volume Title: Palaios
Source: Palaios, 16(5), p.507-523. Publisher: Society of Economic Paleontologists and Mineralogists, Tulsa, OK, United States. ISSN: 0883-1351
Note: In English. Includes appendix. 62 refs.; illus., incl. 2 tables
Summary: The extinction of the Morozovella velascoensis lineage, a group of planktonic foraminifera that dominated tropical assemblages for ∼6.3 m.y., is investigated using an upper Paleocene/lower Eocene section from the central Pacific Ocean (ODP Site 865). Uppermost stratigraphic occurrences of the lineage consist solely of diminutive M. edgari, a species roughly half the size of its ancestor, M. velascoensis. Eigenshape analysis indicates that adult specimens of M. edgari are morphologically similar to small, presumably juvenile, forms of M. velascoensis. The overall stratigraphic succession, where the uppermost occurrences of a lineage are represented by relict populations of minute, juvenilized forms, is consistent with a process called "terminal progenesis." Various lines of evidence indicate that stress-induced size reduction foreshadowed the extinction of other planktonic foraminiferal lineages as well. The ecological cause(s) for the extinction of ancestral M. velascoensis is unclear. Stable isotopic evidence for a progressive deterioration of algal symbiosis was not detected. Specifically, none of the individually-analyzed shells of M. velascoensis were depleted significantly in 13C, nor was there a decrease in the covariance of the δ13C/size relationship. Planktonic foraminiferal δ18O values exhibit a subtle increase over the stratigraphic interval in which the M. edgari extinction is recorded. This inferred tropical cooling appears to be correlative with terrestrial records of cooling from the North American continental interior and northwestern Europe. Thus, it is postulated that climatic variation during the earliest Eocene (∼54.02Ma) played a significant role in shaping biodiversity in the pelagic realm, sealing the doom of the declining M. velascoensis lineage.
Year of Publication: 2001
Research Program: ODP Ocean Drilling Program
Key Words: 10 Paleontology, Invertebrate; 12 Stratigraphy, Historical Geology and Paleoecology; Adaptive radiation; Assemblages; Biologic evolution; C-13/C-12; Carbon; Cenozoic; Eocene; Extinction; Foraminifera; Invertebrata; Isotope ratios; Isotopes; Leg 143; Lower Eocene; Microfossils; Morozovella; Morozovella edgari; Morozovella velascoensis; Morphology; O-18/O-16; ODP Site 865; Ocean Drilling Program; Oxygen; Paleocene; Paleoclimatology; Paleogene; Phylogeny; Planktonic taxa; Protista; Stable isotopes; Tertiary; Upper Paleocene
Coordinates: N182624 N182626 W1793320 W1793321
Record ID: 2002061356
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