Detailed trilobite biostratigraphy across the proposed GSSP for Stage 5 (“Middle Cambrian” boundary) at the Wuliu-Zengjiayan section, Guizhou, China

Abstract

Quarrying across a potential GSSP of the base of Cambrian Stage 5/Series 3 at the Wuliu-Zengjianyan section in south China indicates a significant change in trilobite and brachiopod faunas. The Wuliu Quarry spans approximately 4.5 m across the potential boundary, which is the FAD of Oryctocephalus indicus (Reed, 1910) in the Wuliu-Zengjiayan section of the Kaili Formation. Trilobite taxa found consist of one Pagetia, one Redlichia, one Burlingia, two Olenoides, eleven oryctocephalid, and seven ptychopariid species. Non-trilobite taxa found in the Wuliu Quarry, but not described in this publication, include tubular shells, inarticulate and articulate brachiopods, molluscs, echinoderm plates, sponges, algae, acritarchs, and trace fossils. Collected specimens display both flattening, secondary calcite preservation, and tectonic distortion. Many of the species have previously been based on length to width ratios. Given the range of morphologies demonstrated in these collections, several previously named species have been synonymized. Detailed collections from the Wuliu Quarry show that the faunas of the Ovatoryctocara cf. granulata-Bathyonotus holopygus and the O. indicus zones changed in a 20 cm, relatively barren interval. This faunal turnover does not coincide with a lithologic change and suggests that the section would be a good location for the GSSP of the base of Cambrian Stage 5/Series 3.•

The Burlingiidae (Trilobita): revised generic composition, stratigraphy, and the first species from the early Middle Cambrian of West Gondwana

“…Remarkably, the occurrences of B. primitiva and S. rara correspond to the upper part of the Ovatoryctocara granulata level, that of B. ovata and B. multisegmenta in the original reports (Yuan et al 2002) to the Oryctocephalus indicus level, both levels suggested as candidate for indicating a GGSP for the Cambrian Series 2-3 and Stage 4 -5 boundary (see discussions in Geyer 2005 andPeel 2011 as well as in Zhao et al 2001, 2005, and Sundberg et al 2011. It should be noted that detailed biostratigraphic studies by Sundberg et al (2011) considered B. ovata, B. multisegmenta and B. primitiva all to occur in about the same level in the upper part of the O. granulata -Bathynotus holopygus to O. indicus biozones.…”

“…As discussed in Sundberg et al (2011), most of the small differences between both species could be explained by distortion of the specimens. Differences exist, however, in the number of thoracic segments (nine in B. ovata, 16 in B. multisegmenta).…”

Phylogenetic Analysis of the Spiny Oryctocephalids (Trilobita, Corynexochida?, Oryctocephalidae), Cambrian

“…Curvoryctocephalus originally had two species assigned, but Sundberg et al (2011) and may be represent C. taijiangensis. Oryctocephalus limbatus Chernysheva, 1962 is known from only cranidia of moderate preservation in shale, but has a similar frontal area and cranidial shape to C. taijiangensis and is questionably assigned to this genus.…”

“…Since the time of publication of Sundberg and McCollum (1997), several more oryctocephalids have been described or reillustrated (Blaker and Peel, 1997;Jell and Hughes, 1997;Shabanov et al, 2008aShabanov et al, , 2008bPeng et al, 2009;Geyer and Peel, 2011;Sundberg et al, 2011;this paper) and a possible outgroup has been identified (Sundberg, 2008) allowing a more complete cladistic analysis. PALEOGEOGRAPHIC SETTING In general, the spiny oryctocephalid trilobites occur in low paleolatitude regions of the Cambrian (see Sundberg and McCollum, 1997).…”

Morphological assessment of the Cambrian trilobites Oryctocephalus indicus (Reed 1910) from China and Oryctocephalus ‘reticulatus’ (Lermontova 1940) from Siberia

“…), western USA (Sundberg and McCollum , Sundberg & McCollum ; Sundberg et al . ) and possibly North Greenland (Geyer & Peel ). Its intraspecific morphological variation and ontogenetic development have, however, not been studied in detail.…”