The organic faunal complex of the lower Cambrian Kessyusa Formation of Siberia

Abstract This study describes the Serkinskaya faunal complex of the Siberian lower Cambrian Kessyusa Group, which includes a fragment of gnathobase, several scalids of priapulid-like organisms, various morphotypes of spines, organic films with outgrowths, and other organic remains. Organic microfossils that we identified as gnathobase fragments (a jaw-like fragment and a robust spine with porous structure) were studied via Raman spectroscopy, and phase distribution maps were constructed to identify different kerogens. The jaw-like fragment has heterogeneity on the surface of the microfossil and can be interpreted as reflecting differential preservation of two different layers of the cuticle. The age of these remains is estimated to be Cambrian Fortunian to Stage 2 (Vendian–Cambrian, possibly Tommotian), which makes the identification of gnathobase fragments one of the oldest known occurrences of evidence for durophagy. These findings confirm the presence of filter-feeding, deposit-feeding (priapulids), vertical mixing of the sediment in the first centimeter, predation pressure (cuticle with outgrowths), and possible durophagy in the earliest Cambrian.