Biomechanical stability and sudden change in the evolution of the deep-sea ostracode Poseidonamicus

Author(s): Benson, Richard H.
Author Affiliation(s): Primary:
Smithson. Inst., Washington, DC, United States
Volume Title: Paleobiology
Source: Paleobiology, 9(4), p.398-413. Publisher: Franklin and Marshall College, Department of Geology, Lancaster, PA, United States. ISSN: 0094-8373 CODEN: PALBBM
Note: In English. 16 refs.; illus. incl. 1 table, sketch map
Summary: Changes in shape and in the pattern of the reticulate carapace ornament of 63 representative female ostracode specimens of the deep-sea genus Poseidonamicus from 28 Deep Sea Drilling Project sites, extending over a geographic distance of 40,000 miles and a geologic age of 40×106yr, have been analyzed by Resistant Fit Theta-Rho analysis, conventional least-squares Theta Rho analysis, and by inspection of homologies in the fossae of the reticulum. It is possible to demonstrate that a sudden evolutionary change in the architectural framework of the carapace can be the product of mechanical accommodation under stress to more gradual and general changes in carapace shape. Certain geometric imperatives related to these mechanical needs determine morphologic stability and consequently rates of evolutionary change. In the western deep South Atlantic (near the Vema Channel on the Rio Grande Rise), an important evolutionary "punctuational event" seems to have taken place at about 14 Myr, whereas its concomitant, more gradual transformation is traceable in the shallower eastern South Atlantic (Walvis Ridge). This evolutionary event in Poseidonamicus probably reflects the relatively sudden invasion of deep Antarctic Bottom Water through the Vema Channel resulting from the formation of the East Antarctic ice cap, while the more gradual transition in shallower depths of Walvis Ridge represents a temporary transitory refuge. The problems of recognizing allopatric origins of species in the deep sea compared to in situ sudden transitions caused by biomechanical instability are considered.
Year of Publication: 1983
Research Program: DSDP Deep Sea Drilling Project
Key Words: 10 Paleontology, Invertebrate; Antarctic bottom water; Arthropoda; Atlantic Ocean; Biologic evolution; Cenozoic; Crustacea; Deep Sea Drilling Project; Deep-sea environment; Eocene; Homology; Indian Ocean; Invertebrata; Least-squares analysis; Mandibulata; Marine environment; Microfossils; Morphology; Ostracoda; Pacific Ocean; Paleogene; Paleontology; Poseidonamicus; Punctuated equilibrium; Resistant fit theta-rho analysis; Rho analysis; South Atlantic; Statistical analysis; Tertiary; Vema Channel; Walvis Ridge
Record ID: 1984049277
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute.

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