An early Cambrian pelago-benthic acorn worm and the origin of the hemichordate larva

• Published in: Palaeontologia Electronica
• Main Authors: Yang, Xianfeng, Kimmig, Julien, Cameron, Christopher B., Nanglu, Karma, Kimmig, Sara R., de Carle, Danielle, Zhang, Caixia, Yu, Mengxiao, Peng, Shanchi
• Format: Report
• Language: English
• Published: COQUINA PRESS 2024
• Subjects: new genus; new species; lower Cambrian; Chengjiang; Enteropneusta; Ambulacraria; MACKENZIE MOUNTAINS; ROCKSLIDE FORMATION; DISPERSAL DISTANCE; SPECIES LONGEVITY; EVOLUTION; HARRIMANIIDAE; INVERTEBRATES; MORPHOLOGY; WATERBORNE; Paleontology; Mackenzie mountains
• Online Access: http://ir.nigpas.ac.cn/handle/332004/43534; https://doi.org/10.26879/1356

Enteropneusts (acorn worms) are hemichordates, the sister group to echinoderms. Together they form the clade Ambulacraria, which is closely related to chordates. All three groups appear in the lower Cambrian, but their interrelationships remain problematic, which impedes the understanding of early deuterostome evolution. Enteropneusts are also extremely rare in the fossil record, only a few species are known from Lagerstatten-type deposits. Here, we describe the earliest known enteromens, including tornaria larvae and juveniles, from the lower Cambrian (Epoch 2, Stage 3) Haiyan Lagerstatte, Chengjiang biota, of China. The enteropneust larvae and post-metamorphic juveniles are the first reported in the fossil record and provide direct evidence for a pelago-benthic lifestyle in a Cambrian deuterostome animal, bolstering the hypothesis that an indirect development is primitive to the enteropneusts and maybe the hemichordates or whole of Ambulacraria.