Late Devonian (Famennian) phacopid trilobites from western Xinjiang, Northwest China

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

“…Their age corresponds roughly with the upper Palmatolepis rhomboidea to Palmatolepis marginifera conodont biozones of the Famennian (Suttner et al, 2014). More recently, Crônier and Waters (2022) described the phacopids of the Hongguleleng Formation that were collected from the Bulongguoer Reservoir section (type section of the Hongguleleng Formation) and the Aomage locality by Waters in 1995 and 2005, and they believed these phacopids occurred in the Palmatolepis crepida conodont biozone. However, the stratigraphic data they provided were not consistent with the conodont biozones.…”

“…Recently, Crônier and Waters (2022) described phacopids from the same horizon (upper P. rhomboidea to P. marginifera conodont biozones, rather than the P. crepida Biozone, see the Geological setting and materials section) in the same area and established a new genus, Clarksonops (type species, Clarksonops junggariensis ) on the basis of several fragmented and eroded specimens. They suggested that this new genus differs from genus Omegops or the Omegops specimens from the Honguleleng Formation mainly in that Omegops has a reduced intercalating ring and a distinct postocular pad.…”

“…3e, i, o, p), so I do not think this new genus is sufficiently distinct from Omegops . Conversely, Clarksonops junggariensis is very similar to Omegops xiangi in terms of the length-to-width ratio of the cephalon, the shape and ornamentation of the intercalating ring, the arrangement of eye lenses, and the number of pygidial axial rings and pleural ribs (the number of pleural ribs is six instead of five, see Crônier and Waters, 2022, fig. 3r), so I think Clarksonops specimens from the Hongguleleng Formation may belong to Omegops xiangi .…”

“…The marine deposits are rich in trilobite fossils in this area, but most of these trilobites have been listed only briefly in the Geological Survey Reports from the 1960s to the 1980s or simply described in the Paleontological Atlas of Northwest China (Xinjiang part) (Zhang, 1983). Only a few species have been systematically studied (Xiang, 1981; Guo, 1989; Yuan and Xiang, 1998; Crônier and Waters, 2022), including Omegops from the Hongguleleng Formation in western Junggar, Xinjiang. Omegops in the Hongguleleng Formation has low disparity but high abundance.…”

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

“…Only a few species have been systematically studied (Xiang, *Corresponding author. 1981;Guo, 1989;Yuan and Xiang, 1998;Crônier and Waters, 2022), including Omegops from the Hongguleleng Formation in western Junggar, Xinjiang. Omegops in the Hongguleleng Formation has low disparity but high abundance.…”