Morphology and trunk development of the trilobite Arthricocephalus chauveaui from the Cambrian series 2 of Guizhou, South China

ABSTRACT

The morphology and trunk development of the trilobite Arthricocephalus chauveaui described herein are based on 216 articulated specimens collected from the Lazizhai section of the Balang Formation (Stage 4, Series 2 of the Cambrian) in Jianhe County, Guizhou Province, South China. The new specimens exhibit a relatively complete ontogenetic sequence ranging from the protaspid to holaspid periods and reveal more morphological changes of the species in detail. For example, from degrees 0 to 4, the facial sutures are proparian and then gradually move backward from degree 5, until in the holaspid period, the suture becomes gonatoparian. Based on both linear measurements, we investigate here the morphological variation of some cranial traits throughout ontogeny. Our results demonstrate that the allometric growth pattern shows continuous variations, some of which are related to trunk development. By exploring the trunk segmentation in A.chauveaui, the developmental mode shows that somitogenesis and tagmosis may have developed independently at each meraspid degree beyond degree 0. The holaspid period is consistent with the beginning of the epimorphic phase.

KEYWORDS:

• Arthricocephalus chauveaui
• ontogeny
• trilobite
• Cambrian
• South China

Acknowledgments

I am grateful to three reviewers and the editors for their thoughtful review and helpful suggestions, which improved this manuscript. We would like to express their sincere thanks to professor Yuanlong Zhao, doctors Qiujun Wang, Tian Lan and Yuning Yang from Guizhou University for their kind assistance to this paper, and Zhen Shen, Zefu Liu and Feng Liu for their assistance in fieldworks.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This research was supported by the National Sciences Foundation of China (Grant No. 40672005; 41172005; 41222013); the Major State Basic Research Development Programme of Ministry of Science and Science and Technology of China (Grant No. 2013CB835002; 2015FY310100-5); Guizhou Science and Technology Department, China (Grant No. Gui, Sci. Z.[2014]4003; Gui Sci G[2017] 5788) and China Geological Survey (Grant No. DD20160120-04);.