Bearriverops, a new Lower Ordovician trilobite genus from the Great Basin, western USA, and classification of the family Dimeropygidae

Jonathan M Adrain; Stephen R Westrop

doi:10.1139/e06-103

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Bearriverops, a new Lower Ordovician trilobite genus from the Great Basin, western USA, and classification of the family Dimeropygidae

Journal article

Peer reviewed

Bearriverops, a new Lower Ordovician trilobite genus from the Great Basin, western USA, and classification of the family Dimeropygidae

Jonathan M Adrain and Stephen R Westrop

Canadian journal of earth sciences, Vol.44(3), pp.337-366

03/2007

DOI: 10.1139/e06-103

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Abstract

Bearriverops n. gen. is a distinctive clade of small, vaulted trilobites from the Lower Ordovician (Ibexian Series; Stairsian Stage) of Utah and Idaho. The genus includes at least seven new species known from silicified material of which five are well enough known to name: B. alsacharovi, B. borderinnensis, B. deltaensis, B. ibexensis, and B. loganensis (the type species). All are known from the lower Fillmore Formation in western Utah; B. alsacharovi and B. loganensis are also known from the Garden City Formation of southeastern Idaho. Both units record deposition in shallow subtidal environments above storm wave base. Bearriverops is characterized particularly by a suite of pygidial apomorphies apparently related to spiral enrollment. Its close relatives include a large group of mostly undescribed Skullrockian and Stairsian species with more conventional spinose pygidia. Together, the taxa are referred to Dimeropygidae, which is considered a senior synonym of Toernquistiidae. Cladistic parsimony analysis of Bearriverops indicates that B. alsacharovi and B. borderinnensis are sister taxa, and that B. loganensis, B. deltaensis, and the plesiomorphic B. ibexensis are successive sister taxa to this clade.

Arthropoda

Basin and Range Province

Bear Lake County Idaho

Bearriverops

biologic evolution

biometry

cladistics

classification

Dimeropygidae

Fillmore Formation

Garden City Formation

Great Basin

Ibexian

Idaho

Invertebrata

Invertebrate paleontology

Lower Ordovician

Millard County Utah

morphology

new taxa

North America

Ordovician

Paleozoic

parsimony

regression analysis

southeastern Idaho

statistical analysis

synonymy

taxonomy

Toernquistiidae

Trilobita

Trilobitomorpha

United States

Utah

Western U.S

western Utah

Details

Title: Subtitle: Bearriverops, a new Lower Ordovician trilobite genus from the Great Basin, western USA, and classification of the family Dimeropygidae
Creators: Jonathan M Adrain - University of Iowa
Stephen R Westrop - University of Oklahoma
Resource Type: Journal article
Publication Details: Canadian journal of earth sciences, Vol.44(3), pp.337-366
Publisher: National Research Council of Canada
DOI: 10.1139/e06-103
ISSN: 0008-4077
eISSN: 1480-3313
Language: English; French
Date published: 03/2007
Academic Unit: Earth and Environmental Sciences
Record Identifier: 9984229171702771

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