Three Indeterminate Forms of Scalidophoran Worms from the Cambrian Fortunian of South China

Abstract

AbstractA wide variety of scalidophoran worms have been found in the Cambrian Fortunian in recent years, suggesting that scalidophorans diversified during this age. Here, we report new scalidophoran material obtained from the 2nd member of the Kuanchuanpu Formation (Fortunian Stage) in Zhangjiagou Lagerstätte, Xixiang County, Shaanxi Province, South China. Three indeterminate forms of scalidophoran worms are described in detail. The morphology of these worms differs from that of any coeval worms and may represent new taxa. However, because these fossils are fragmented and lack detailed information on the arrangement pattern of introvert scalids, they are named here in open nomenclature. This study enriches the diversity of the earliest scalidophorans to 7 genera and species and 10 indeterminate forms. Based on the new fossils, Fortunian scalidophoran worms can be divided into three categories: (1) worms with microannuli; (2) worms with macroannuli; and (3) worms without annuli.