Journal article
The Early Ordovician (Floian) bathyurid trilobite Jimlochaspis n. gen., with species from western Utah and Greenland
Palaeoworld, Vol.35(4), 201110
08/2026
DOI: 10.1016/j.palwor.2026.201110
Abstract
Jimlochaspis n. gen. (type species J. copei n. sp.) is a distinctive new bathyurid trilobite from the Floian (Blackhillsian) Fillmore Formation of western Utah. Phylogeny of Bathyuridae is not well understood. The family was most diverse during the late Tremadocian and Floian. By the Late Ordovician it was reduced to only two genera, the closely related Bathyurus and Raymondites. They form a group with highly derived morphology, including secondarily conterminant hypostomes and absence of a preglabellar field. The sister taxon of this group has been obscure, but the pygidial morphology of Jimlochaspis has shared features (a flattened border with the pleural ribs, pleural, and interpleural furrows expressed on it and an unusually elongate axial terminal piece) that closely match those of the oldest species of Bathyurus, which may indicate phylogenetic relationship and a Floian “root” for the Bathyurus group. Two species from western Utah, including the type, are known from well preserved secondarily silicified specimens. One lacks any recovered cranidia and is reported in open nomenclature (Jimlochaspis n. sp. A). These species are quite similar, but can be clearly differentiated in a range of pygidial features (width of border, relative size of posteromedian spine, posteromedian inflation of border). Goniurus boggildi Poulsen, 1927, from the Floian Nunatami Formation of northwestern Greenland, has a lectotype pygidium (selected herein) that closely resembles those of the type species, and the species is assigned with confidence to the new genus. However, the poorly preserved cranidium and librigena assigned to the species by Poulsen are not closely similar to those of the type species, and there is reason to doubt the association of sclerites.
Details
- Title: Subtitle
- The Early Ordovician (Floian) bathyurid trilobite Jimlochaspis n. gen., with species from western Utah and Greenland
- Creators
- Jonathan M. Adrain - University of IowaFrancesc Pérez-Peris - University of Iowa
- Resource Type
- Journal article
- Publication Details
- Palaeoworld, Vol.35(4), 201110
- DOI
- 10.1016/j.palwor.2026.201110
- ISSN
- 1871-174X
- eISSN
- 1875-5887
- Publisher
- Elsevier B.V
- Grant note
- NSF: EAR 9973065, EAR 0308685, DEB 0716065
Research has been supported by NSF grants EAR 9973065, EAR 0308685, and DEB 0716065. The field pro-gram began as a collaboration with Steve Westrop, who logged Section H. Neo McAdams assisted with fieldwork and acid processing. Brian Beck, Alex Bradley, Rebecca DeKoster, Talia Karim, Sarah Losso, Charles Monson, Reuben Ng, Dave Schultz, and Mark Spencer assisted in the field. Tiffany Adrain provided assistance with SUI numbers and curation. David Harper, then of the Geolo-gisk Museum, Copenhagen, facilitated loan of the type material of Jimlochaspis boggildi . Reviews by Lucy McCobb and Xin Wei improved the manuscript.
- Language
- English
- Electronic publication date
- 04/2026
- Date published
- 08/2026
- Academic Unit
- School of Earth, Environment, and Sustainability
- Record Identifier
- 9985152086702771
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