Systematics and affinity of the Lower Ordovician (Tulean, lower Floian) trilobite Psalikilopsis

Jonathan M Adrain; Neo E. B McAdams; Stephen R Westrop; Talia S Karim

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Systematics and affinity of the Lower Ordovician (Tulean, lower Floian) trilobite Psalikilopsis

Journal article

Peer reviewed

Systematics and affinity of the Lower Ordovician (Tulean, lower Floian) trilobite Psalikilopsis

Jonathan M Adrain, Neo E. B McAdams, Stephen R Westrop and Talia S Karim

Memoir ... of the Association of Australasian Palaeontologists, Vol.42, pp.369-416

2012

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Abstract

Psalikilopsis Ross, 1953, has been known from a single species and interpreted as a "hystricurine" ancestral to some, but not all, "bathyurids". Comprehensive revision of the type species and the description of three new species demonstrate that the taxon is ingroup Bathyuridae. The unusual morphology of its more derived species is associated with a change from normal bathyurid sphaeroidal enrolment to spiral enrolment, with part of the pygidium tucked inside the cephalon, stopped medially by a pygidial spine docking against a medially modified anterior border. The oldest and apparently basal species lacks these modifications and is of "normal" bathyurid morphology. The genus occurs in lower Floian (Tulean) Psalikilus spinosum, Hintzeia celsaora, and Psalikilopsis cuspidicauda zones in Idaho, Utah, and Nevada, and its striking morphology and common occurrence make it biostratigraphically significant. A pygidium from the Fort Cassin Formation of New York, and two species illustrated in open nomenclature from the Shallow Bay Formation of Newfoundland demonstrate the occurrence of Psalikilopsis in eastern Laurentia. The eastern Laurentian species appear to be younger than those from western Laurentia. New species are Psalikilopsis paracuspidicauda (Psalikilopsis cuspidicauda Zone), P. redfordi (H. celsaora Zone), and P. newmani (Psalikilus spinosum Zone).

affinities

Arthropoda

Basin and Range Province

biostratigraphy

Canada

Eastern Canada

Floian

Great Basin

Idaho

Invertebrata

Invertebrate paleontology

lower Floian

Lower Ordovician

morphology

Nevada

new taxa

New York

Newfoundland

Newfoundland and Labrador

North America

ontogeny

Ordovician

Paleozoic

phylogeny

Psalikilopsis

Psalikilopsis newmani

Psalikilopsis paracuspidicauda

Psalikilopsis redfordi

taxonomy

Trilobita

Trilobitomorpha

Tulean

United States

Utah

Details

Title: Subtitle: Systematics and affinity of the Lower Ordovician (Tulean, lower Floian) trilobite Psalikilopsis
Creators: Jonathan M Adrain - University of Iowa
Neo E. B McAdams
Stephen R Westrop
Talia S Karim
Contributors: John R Laurie (Editor) - Geoscience Australia
J. R Paterson (Editor)
G. A Brock (Editor)
Resource Type: Journal article
Publication Details: Memoir ... of the Association of Australasian Palaeontologists, Vol.42, pp.369-416
Publisher: Association of Australasian Palaeontologists
ISSN: 0810-8889
Alternative title: Cambro-Ordovician studies; IV
Language: English
Date published: 2012
Academic Unit: Earth and Environmental Sciences
Record Identifier: 9984229304202771

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