New palaeoscolecidian worms from the Lower Ordovician Madaoyu Formation with specialised morphological characters and functional morphology

A new non-mineralised fauna was recently discovered in the Lower Ordovician Madaoyu Formation near Liexi Township, West Hunan Province, South China. Diverse animals are preserved in a thin layer of siltstone interbedded within the limestone. The most peculiar group among this new Fauna is a large quantity of palaeoscolecidan worms with multiple instars, which are only represented by trunks without any other soft tissues such as the introvert, pharynx, and intestine being preserved. The unique characteristic of these worms are that they have a dorsal-ventral differentiation of plates, which are arranged in longitudinal lines, this suggests that the worms probably were exquisite bottom crawlers. The palaeoscolecidans are uniform in morphology and attributed to a new genus and species, Liexiscolex hunanensis Liu & Huang, gen. et sp. nov. This discovery not only enriches our knowledge of the anatomy and palaeoecology but also helps us understand the evolution of palaeoscolecidan worms. Furthermore, it provides a better comprehension of the Lower Ordovician Liexi fauna in South China.