Archaeopriapulida is a group of priapulid worms known from Cambrianlagerstätte.[3] The group is closely related to, and very similar to, the modern Priapulids.[4] It is unclear whether it is mono- or polyphyletic.[5] Despite a remarkable morphological similarity to their modern cousins,[6] they fall outside of the priapulid crown group, which is not unambiguously represented in the fossil record until the Carboniferous.[7] In addition to well-preserved body fossils, remains of several archaeopriapulid taxa are known to have been preserved primarily as organic microfossils, such as isolated scalids and pharyngeal teeth.[8][9][10] They are probably closely related or paraphyletic to the palaeoscolecids; the relationship between these basal worms is somewhat unresolved.[5]
^Conway Morris, S. (1979). "The Burgess Shale (Middle Cambrian) Fauna". Annual Review of Ecology and Systematics. 10: 327–349. doi:10.1146/annurev.es.10.110179.001551.