A new scalidophoran animal from the Cambrian Fortunian Stage of South China and its implications for the origin and early evolution of Kinorhyncha

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

“…The Fortunian scalidophorans already have a relatively high diversity, with 7 genera and species and 10 indeterminate forms now reported. They can be divided into three categories based on the type of annuli: (1) worms with microannuli, which are dense and numerous, similar to priapulid-like forms, including Eopriapulites (Liu et al, 2014;Shao et al, 2020b) and Xinliscolex (Zhang, 2022); (2) worms with macroannuli that are wider and resemble kinorhynch-like forms, including Eokinorhynchus (Zhang et al, 2015), Zhongpingscolex (Shao et al, 2020a), Qinscolex, Shanscolex (both in , Dahescolex (Shao et al, 2020b), forms 1-3 and Based on the characteristics of the annulus, there may be a closer affinity between Eopriapulites and Xinliscolex. Likewise, there may be closer affinities between form 3 sensu Liu et al, 2019, worm A and other kinorhynch-like forms.…”

“…Scalidophorans are rare components of small-shellyfossil assemblages in the Lower Cambrian Kuanchuanpu Formation (Fortunian Stage) in Zhangjiagou Lagerstä tte, Xixiang County, Shaanxi Province, South China. To date, seven scalidophoran genera and species, as well as eight indeterminate forms, have been reported in this stage, and recent reports on new types of fossil scalidophorans (Liu et al, 2014(Liu et al, , 2019Zhang et al, 2015Zhang et al, , 2018Shao et al, 2016Shao et al, , 2018Shao et al, , 2020aZhang, 2022) imply a higher diversity in this stage. As the earliest unambiguous fossils of scalidophorans, these fossils are of great significance for understanding the origin and early evolution of Cycloneuralia and Ecdysozoa (Wang et al, 2019(Wang et al, , 2020.…”

“…Early cycloneuralians were dominated by scalidophorans, which are highly diverse components that are commonly found in Cambrian strata, including Markuelia (Dong et al, 2004(Dong et al, , 2005(Dong et al, , 2010Donoghue and Dong, 2005;Haug, et al, 2009), Priapulids (Briggs et al, 1994;Maas et al, 2006;Maas, 2013;Liu et al, 2014;Smith et al, 2015;Hou et al, 2017), kinorhynch-like worms (Zhang et al, 2015;Fu et al, 2019;Shao et al, 2020a), Loricifera (Maas et al, 2009;Peel et al, 2013;Harvey and Butterfield, 2017) and palaeoscolecids (Müller and Hinz-Schallreuter, 1993;Zhang and Pratt, 1996;Han et al, 2007;Duan et al, 2012;Duan and Dong, 2013;Liu et al, 2018).…”

A New Chengjiang Worm Sheds Light on the Radiation and Disparity in Early Priapulida

“…The relation of early Paleozoic scalidophorans to extant lineages of the group is not strongly established [ 3 , 4 , 5 ]. The majority of them fall into the Paleoscolecida, an extinct group of strongly ornamented worms [ 4 , 6 , 7 ], whereas others are considered as more or less closely related to Priapulida [ 8 , 9 , 10 , 11 ], Loricifera [ 12 , 13 ], Kinorhyncha [ 14 , 15 ] and possibly Nematomorpha [ 16 ]. These scalidophorans share key morphological traits such as an annulated trunk and more importantly an eversible introvert divided into three parts, each bearing specific and regularly distributed cuticular ornaments [ 8 , 10 , 11 ].…”