A long-headed Cambrian soft-bodied vertebrate from the American Great Basin region

• Published in: Royal Society open science Vol. 11; no. 7; p. 240350
• Main Authors: Lerosey-Aubril, Rudy, Ortega-Hernández, Javier
• Format: Journal Article
• Language: English
• Published: England The Royal Society 01.07.2024
• Subjects: Earth and Environmental Science; exceptional preservation; Laurentia; Marjum Formation; Miaolingian; planktonekton; vertebrate origin; Miaolingian; planktonekton; vertebrate origin; Laurentia; exceptional preservation; Marjum Formation
• ISSN: 2054-5703; 2054-5703
• DOI: 10.1098/rsos.240350

The fossil record suggests that chordates might have been minor components of marine ecosystems during the first major diversification of animal life in the Cambrian. Vertebrates are represented by a handful of rare soft-bodied stem-lineage taxa known from Konservat-Lagerstätten, including and from the Stage 3 of South China, and and from Stage 4-Drumian deposits of northeast USA and British Columbia. Here, we describe the first soft-bodied vertebrate from the American Great Basin, a region home to a dozen Cambrian Konservat-Lagerstätten. Found in the Drumian Marjum Formation of Utah, gen. et sp. nov. is characterized by a finless torpedo-shaped body that includes a snout-like anterior head bearing anterolateral eyes, approximately 25 thick myomeres, a large branchial chamber with a keel and approximately seven putative dorsal bars and a spiniform caudal process. Using Bayesian inference, our analysis recovers within the vertebrate stem, closer to the crown than , and , where it forms a polytomy with its Laurentian relatives, and , and a scion consisting of conodonts and crown-group vertebrates. Based on the eye orientation and absence of fins we tentatively reconstruct as a pelagic organism with limited swimming abilities (planktonektic).