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Variation in eye lenses of two new Late Devonian phacopid trilobites from western Junggar, NW China

Zong Ruiwen
Variation in eye lenses of two new Late Devonian phacopid trilobites from western Junggar, NW China
Journal of Paleontology (July 2023) 97 (4): 891-905


The suborder Phacopina, characterized by schizochroal eyes, is among the most common groups of trilobites in Devonian strata. The marine sediments of the Famennian in western Junggar, Xinjiang, contain abundant low-disparity phacopids, which have previously been designated to Omegops accipitrinus mobilis, Phacops circumspectans tuberculosus, and Omegops cornelius on the basis of small numbers of poorly preserved specimens. In this study, these phacopids were identified as two new species of Omegops, O. honggulelengensis n. sp. and O. xiangi n. sp., on the basis of nearly 200 well-preserved specimens. The intraspecific variations of eye lenses of these specimens were quantitatively analyzed. On the basis of differences in the total number, number of dorsoventral files, and arrangement of the eye lenses, the absence of lenses in the middle part of the visual surface, and asymmetry of the number and/or arrangement of lenses in the two eyes, it was concluded that the reasons for intraspecific variation in eye lenses of Late Devonian Omegops from western Junggar were different from previously described factors but were likely genetic or embryological malfunctions or abnormalities caused by pathological conditions. Diversity of lenses in the schizochroal eyes shows that the number and arrangement of eye lenses was not stable in Phacopina. Therefore, many specimens are needed for quantitative study to determine the true characteristics of the number or arrangement of eye lenses when these features are used in the systematic taxonomy of Phacopina. UUID:

ISSN: 0022-3360
EISSN: 1937-2337
Serial Title: Journal of Paleontology
Serial Volume: 97
Serial Issue: 4
Title: Variation in eye lenses of two new Late Devonian phacopid trilobites from western Junggar, NW China
Author(s): Zong Ruiwen
Affiliation: China University of Geosciences-Wuhan, State Key Laboratory of Biogeology and Environmental Geology, Wuhan, China
Pages: 891-905
Published: 202307
Text Language: English
Publisher: Cambridge University Press for the Paleontological Society, Lawrence, KS, United States
References: 62
Accession Number: 2024-002904
Categories: Invertebrate paleontology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. strat. col., geol. sketch map
N46°34'00" - N46°34'00", E85°58'00" - E85°58'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2024, American Geosciences Institute. Abstract, Copyright, The Paleontological Society. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 2024
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