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Early Ordovician ostracods from Argentina; their bearing on the origin of binodicope and palaeocope clades

Maria Jose Salas, Jean Vannier and Mark Williams
Early Ordovician ostracods from Argentina; their bearing on the origin of binodicope and palaeocope clades
Journal of Paleontology (November 2007) 81 (6): 1384-1395

Abstract

New species of ostracods are described from the Tremadoc of the Cordillera Oriental (Argentina). These are among the earliest well-documented records of Ostracoda sensu stricto. The ostracod assemblages are sourced from shallow marine clastics and are dominated by palaeocopes (Eopilla waisfeldae n. sp., Nanopsis coquena n. sp.), and the binodicope Kimsella luciae n. gen. and sp. Eopilla and Kimsella show affinities with species from paleocontinental Gondwana (e.g., Ibero-Armorica, Turkey, Australia, Carnic Alps), but Nanopsis is previously known only from paleocontinental Baltica. This study confirms that two of the major clades of Ordovician ostracods, namely the Binodicopa and the Palaeocopa, were already geographically widespread during the late Tremadoc, suggesting a still earlier origin for these groups, possibly from within the Cambrian to Early Ordovician Bradoriida. Evidence from soft-part anatomy indicates that phosphatocopids, the other group hypothesized to be ancestral ostracods, have apomorphies that preclude them as direct ancestors. The origin of ostracods is more likely to be found within the Bradoriida, a probable polyphyletic group that resembles Early Ordovician ostracods in the external sculpture of their bivalved carapace. Evidence from carapace morphology suggests that the ancestors of true ostracods might lie within the bradoriid groups Beyrichonidae and Hipponicharionidae, a hypothesis that can only truly be tested when more evidence from fossilized soft tissues becomes available.


ISSN: 0022-3360
EISSN: 1937-2337
Coden: JPALAZ
Serial Title: Journal of Paleontology
Serial Volume: 81
Serial Issue: 6
Title: Early Ordovician ostracods from Argentina; their bearing on the origin of binodicope and palaeocope clades
Affiliation: Universidad Nacional de Cordoba, Centro de Investigaciones Paleobiologicas, Cordoba, Argentina
Pages: 1384-1395
Published: 200711
Text Language: English
Publisher: Paleontological Society, Lawrence, KS, United States
References: 64
Accession Number: 2008-001053
Categories: Invertebrate paleontology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. strat. cols., 2 plates, 1 table, geol. sketch map
S25°00'00" - S23°30'00", W66°00'00" - W65°00'00"
Secondary Affiliation: Universite Claude Bernard-Lyon I, FRA, FranceUniversity of Portsmouth, GBR, United Kingdom
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, The Paleontological Society. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 200801
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