New materials reveal Shaanxilithes as a Cloudina-like organism of the late Ediacaran

Shaanxilithes is a potential index fossil of late Ediacaran for its cosmopolitan occurrences and narrow stratigraphic range. However, its morphology and taxonomy has long been controversial and its biological affinities remain problematic, with interpretations ranging from pogonophorans, sedimentary structures, trace fossils, algae, to metazoans of uncertain phylogeny. New materials from the late Ediacaran strata of North China reveal that Shaanxilithes is a nested internal tube encased within a flexible, annulated external tube, rather than a ribbon-shaped fossil as previously suggested. The co-occurred forms previously described as Helanoichnus, Shaanxilithes erodus and Palaeopascichnus, are reconsidered as taphonomic variations of Shaanxilithes ningqiangensis. On the basis of anatomical details, Shaanxilithes is assigned to the contemporaneous cloudinids, a group of late Ediacaran enigmatic tubular forms including the well-known Cloudina.

Automated summary

Shaanxilithes is a potential index fossil of the late Ediacaran period due to its widespread distribution and narrow stratigraphic range. Its actual morphology and taxonomic classification have long been controversial, with varied interpretations of its biological affinities. New research has revealed Shaanxilithes to be classified as a cloudinid based on anatomical details.