Burrows filled with faecal pellets from the Cambrian (Stage 4) Guanshan biota of South China and their palaeoecological implications

Yazhou Hu,Dirk Knaust,Yue Liang,Lars E Holmer,Zhifei Zhang

doi:10.1016/j.palaeo.2021.110249

Yazhou Hu, Dirk Knaust + Show 3 more

Open Access

https://doi.org/10.1016/j.palaeo.2021.110249

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Abstract

Recent excavations of the Guanshan biota at the Shijiangjun section in the eastern Yunnan Province, South China, have revealed many well-defined faecal pellets and related trace fossils. These can be assigned to three morphotypes, which have affinities with the ichnogenera Tomaculum, Alcyonidiopsis and Tubulichnium. Morphotype 1 is an unbranched burrow filled with randomly distributed faecal pellets. Morphotype 2 is a string-shaped burrow without branching, containing intensely compacted faecal pellets. Morphotype 3 comprises unbranched burrows with a fill of faecal pellets and a central cavity. The ellipsoidal faecal pellets in morphotype 1 and 2 can be assigned to Coprulus oblongus. They are morphologically similar to the excrements produced by modern deposit-feeding polychaetes, as well as the gut content of early Cambrian polychaete worms (Guanshanchaeta felicia) from the Guanshan biota and priapulid worms (Selkirkia) from the Xiaoshiba Lagerstätte. This analogy suggests polychaetes and priapulid worms as potential producers of these burrows and that a diverse range of digestive methods had already been established in the Cambrian Stage 4 ca. 510 Ma ago. Morphotype 3 is interpreted to be related to the storage of faecal pellets and possibly for cultivation of bacteria, which would represent an early case of this behaviour. The discovery of this diverse suite of burrows with faecal pellets indicates that the origin of diverse deposit-feeding strategies in worms can be traced back to at least the Cambrian Stage 4.

Highlights

Trace fossils represent a vital record of the interaction between or ganisms and their associated substrate and provide evidence of their behaviour (Seilacher, 1967; Pemberton et al, 1992; Buatois and Mangano, 2011)
Burrows filled with faecal pellets are reported from the Guanshan biota, which have an affinity to Tomaculum and Alcyonidiopsis but are assigned to three distinct morphotypes due to nomenclatural issues
The faecal pellets can be assigned to the coprolite ichnotaxon Coprulus oblongus, and comparison with modern analogues as well as the bodyfossil content of the lagerstatte favours polychaetes and priapulids as their producers

Summary

Introduction

Trace fossils represent a vital record of the interaction between or ganisms and their associated substrate and provide evidence of their behaviour (Seilacher, 1967; Pemberton et al, 1992; Buatois and Mangano, 2011). The evolution of metazoans, especially the develop ment of new behaviours, can be directly inferred from the investigation of trace fossils (Frey, 1973). Some trace fossils, such as coprolites, pro vide unique information about the diet and associated feeding strategies of their producers (e.g. Vannier and Chen, 2005; Shen et al, 2014; Kimmig and Strotz, 2017; Kimmig and Pratt, 2018). Only few studies dealing with coprolites try to investigate the feeding strategies of deposit feeders. Little research is related to the ethological inter pretation of their trace makers

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