Acosmia
Acosmia is an extinct genus of marine worm from the Cambrian aged Chengjiang biota of Yunnan, China. It is represented by a single rare species, Acosmia maotiania, that reached 45 mm in length and 9 mm in width. It was likely a burrowing animal that fed by deposit feeding. While originally suggested it to be a priapulid, a 2020 study proposed to be a stem-group ecdysozoan, due to lacking the radial pharygneal armature that characterises modern ecdysozoans, including priapulids. Later studies suggested that Acosmia was more likely a crown-group ecdysozoan possibly alied with nematoids.