Cycloneuralia

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

“…As summarized by Giribet and Edgecombe (2017), Cycloneuralia is usually considered non-monophyletic in molecular studies, while most morphological analyses suggest that Cycloneuralia is a monophyletic group (Dong et al, 2004(Dong et al, , 2010Harvey et al, 2010;Wills et al, 2012) that can be sub-divided into two sister groups: Nematoida (Nematoda and Nematomorpha) and Scalidophora (Priapulida, Kinorhyncha, and Loricifera). The main differences between the two groups are the presence of internally hollow scalids and body wall muscles in scalidophorans but the absence of these structures in nematoids (Lemburg, 1995;Hejnol, 2015). Previous molecular studies have proposed that Cycloneuralia was the first branch of Ecdysozoa in the Ediacaran period, with cycloneuralians radiating during the early Cambrian epoch (Rota-Stabelli et al, 2013;Cunningham et al, 2017).…”

A priapulid larva from the middle Cambrian (Wuliuan Stage) of North Greenland (Laurentia)

“…Present day priapulids comprise a small group of cyclo neuralian worms containing only about 22 described species (Maas 2013, SchmidtRhaesa 2013, Hejnol 2015, SchmidtRhaesa et al 2017, SchmidtRhaesa & Freese 2019. Most species are small and live infaunally, com monly as meiofauna, but Shirley & Storch (1999) de scribed specimens that attained a length of 39 cm.…”

“…However, Peel (2010a) and Peel et al (2013) considered that circumoral, multicuspidate, hexaradially disposed, grasping denticles in the lorica of Sirilorica Peel, 2010a from the Sirius Passet Lagerstätte (Cambrian Series 2) of North Greenland emphasised the relationship between these Cambrian fossils and living loriciferans and nematomorphans. As a consequence, Peel et al (2013) considered that the development of a lorica was not a unifying character for priapulids and loriciferans within Vinctiplicata, noting in passing the morphological similarity between the loricas of Sirilorica and the present day rotifer Notholca ikaitophila Sørensen & Kristensen, 2000. Hejnol (2015 considered the resemblance of loriciferans to priapulid loricate larvae to be superficial.…”