Journal article
The trilobites Smoothcanyonops gen. nov. and Ceeops gen. nov. from the Early Ordovician (mid-Tremadocian; Stairsian) of the Great Basin, western USA
Bulletin of geosciences, Vol.101(1), pp.49-64
2026
DOI: 10.3140/bull.geosci.1958
Abstract
Extensive field-based sampling of the shallow water trilobite faunas of the northern Laurentian palaeo-margin (present day western North America) has yielded an abundance of well preserved, secondarily silicified, faunas spanning the Lower Ordovician. As sampling has accumulated, some very rare species have been revealed. It is unusual to encounter new post-Cambrian trilobites whose family-group affinity is obscure, but two new Stairsian (mid Tremadocian) genera contain reasonably well known species with effaced morphologies that have no obvious close comparisons among other Ordovician taxa. Smoothcanyonops gen. nov. (type species S. smoothcanyonensis sp. nov.) includes species with dorsally smooth, considerably effaced morphology, apparently with yoked librigenae. A second assigned species is S. middlensis sp. nov. Ceeops gen. nov. (type and only species C. housensis sp. nov.) is also mostly unsculptured and effaced, but has a greatly anteriorly expanded cranidium, broad librigenae, and very broad cephalic doublure. While their thin cuticles, general lack of sculpture, and weakly expressed dorsal furrows indicate they could be representatives of the same family-group taxon, there are also considerable morphological differences between them. Among other trilobites, they both have some resemblances, particularly in librigenal morphology, to bathyurids. However they are older than the oldest widely agreed species of bathyurids and they lack many bathyurid features. At present their affinity is difficult to assess with any confidence.
Details
- Title: Subtitle
- The trilobites Smoothcanyonops gen. nov. and Ceeops gen. nov. from the Early Ordovician (mid-Tremadocian; Stairsian) of the Great Basin, western USA
- Creators
- Jonathan M. Adrain - School of Earth, Environment, and Sustainability, University of Iowa, Iowa City, IA, United States
- Resource Type
- Journal article
- Publication Details
- Bulletin of geosciences, Vol.101(1), pp.49-64
- DOI
- 10.3140/bull.geosci.1958
- ISSN
- 1214-1119
- eISSN
- 1802-8225
- Publisher
- CZECH GEOLOGICAL SURVEY
- Grant note
- NSF: EAR 9973065, EAR 0308685, DEB 0716065 Department of Earth and Environmental Sciences
Research has been supported by NSF grants EAR 9973065, EAR 0308685, and DEB 0716065. Sampling of Section C in 2024 was greatly assisted by E. Bley, T. Camus, F. Perez-Pens, and R. Shanks. Perez-Peris, Camus, and Bley acid-processed the silicified samples from Section C. Stephen R. Westrop logged all of the sections, and has collaborated on the overall research program. Francesc Perez-Peris read the manuscript. The Department of Earth and Environmental Sciences (now incorporated into the School of Earth, Environment, and Sustainability) provided considerable financial support for fieldwork in 2023-2024. Tiffany S. Adrain provided assistance with SUI numbers and curation. Reviewers J.D. Loch and A.W.A. Rushton and editor N.C. Hughes made suggestions and corrections that improved the manuscript.
- Language
- English
- Date published
- 2026
- Academic Unit
- School of Earth, Environment, and Sustainability
- Record Identifier
- 9985164715502771
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