Morphological variability of menardiform globorotalids in the Atlantic Ocean during mid-Pliocene

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doi: 10.1016/j.marmicro.2012.12.001
Author(s): Mary, Yannick; Knappertsbusch, Michael W.
Author Affiliation(s): Primary:
Natural History Museum Basel, Basel, Switzerland
Volume Title: Marine Micropaleontology
Source: Marine Micropaleontology, Vol.101, p.180-193. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0377-8398 CODEN: MAMIDH
Note: In English. Includes appendix. 72 refs.; illus., incl. 1 plate, 1 table, sketch maps
Summary: The morphological variation of the planktonic foraminifera plexus of Globorotalia (Menardella) (Bandy, 1972) has been studied in a Pliocene time-slice at 3.2 Ma. Using a combination of size, linear shell measurements and shape analysis, an extended morphological protocol is explored in order to define morphological subgroups within the Menardella subgenus (Bandy, 1972). Isochronous samples at 3.2 Ma have been selected at five ODP/IODP Sites in the low latitude Atlantic Ocean, in which up to 600 specimens per sample have been oriented, imaged and analyzed using a new automated prototype for morphological analysis called AMOR. Multimodal size frequency distribution is related to the occurrence of several distinct populations. Three main ubiquitous populations of such menardellids are isolated, next to two additional biogeographically limited subgroups. These populations strongly differ in abundance and size. Using morphological classifiers, subpopulations are distinguished among these populations, leading to the establishment of seven different morphotypes informally named: MA, MB, MC1, MC2, MC3, SH1 and SH2. These morphotypes are assigned to formal species, i.e., MA corresponds to Globorotalia (Menardella) menardii, MB to G. (M.) limbata, SH1 to G. (M.) exilis, and SH2 to G. (M.) pertenuis. In contrast, the species G. (M.) multicamerata is interpreted as being composed of three distinct morphotypes, sharing a similar size range, but differing in shell morphology. Morphotype MC1 shows thin and elongated chambers, whereas morphotype MC2 is characterized by a thick and robust test. MC3 is inflated with a distinct flexure in the final chamber. Size differences are linked to variations in habitat temperature and oxygenation, with the exception of G. (M.) multicamerata morphotypes, which are probably adapted to a productivity gradient. Abstract Copyright (2013) Elsevier, B.V.
Year of Publication: 2013
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
ODP Ocean Drilling Program
Key Words: 10 Paleontology, Invertebrate; Atlantic Ocean; Automated Measurement System for Shell Morphology; Biogeography; Biometry; Cape Verde Rise; Caribbean Sea; Ceara Rise; Cenozoic; DSDP Site 502; Deep Sea Drilling Project; Equatorial Atlantic; Foraminifera; Globigerinacea; Globorotalia; Globorotaliidae; IPOD; Invertebrata; Leg 108; Leg 154; Leg 68; Menardella; Microfossils; Middle Pliocene; Morphology; Neogene; North Atlantic; ODP Site 659; ODP Site 661; ODP Site 667; ODP Site 925; Ocean Drilling Program; Planktonic taxa; Pliocene; Principal components analysis; Protista; Rotaliina; Sierra Leone Rise; Size; Statistical analysis; Tertiary; Tests; Vicariance
Coordinates: N180437 N183438 W0210134 W0210135
N043348 N092649 W0192310 W0215441
N041215 N041216 W0432920 W0432922
N112925 N112925 W0792247 W0792247
Record ID: 2014007272
Copyright Information: GeoRef, Copyright 2017 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands