title: Haootia quadriformis n. gen., n. sp., interpreted as a muscular cnidarian impression from the Late Ediacaran period (approx. 560 Ma).
abstract: Muscle tissue is a fundamentally eumetazoan attribute. The oldest evidence for fossilized muscular tissue before the Early Cambrian has hitherto remained moot, being reliant upon indirect evidence in the form of Late Ediacaran ichnofossils. We here report a candidate muscle-bearing organism, Haootia quadriformis n. gen., n. sp., from approximately 560 Ma strata in Newfoundland, Canada. This taxon exhibits sediment moulds of twisted, superimposed fibrous bundles arranged quadrilaterally, extending into four prominent bifurcating corner branches. Haootia is distinct from all previously published contemporaneous Ediacaran macrofossils in its symmetrically fibrous, rather than frondose, architecture. Its bundled fibres, morphology, and taphonomy compare well with the muscle fibres of fossil and extant Cnidaria, particularly the benthic Staurozoa. Haootia quadriformis thus potentially provides the earliest body fossil evidence for both metazoan musculature, and for Eumetazoa, in the geological record.
authors.affiliation: Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK agscl2@cam.ac.uk.
authors.forename: Alexander G
authors.initials: AG
authors.lastname: Liu
authors.affiliation: Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, UK.
authors.forename: Jack J
authors.initials: JJ
authors.lastname: Matthews
authors.affiliation: Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, UK.
authors.forename: Latha R
authors.initials: LR
authors.lastname: Menon
authors.affiliation: Department of Earth Sciences, Memorial University of Newfoundland, 300 Prince Philip Drive, St John's, Newfoundland and Labrador, Canada A1B 3X5.
authors.forename: Duncan
authors.initials: D
authors.lastname: McIlroy
authors.affiliation: Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, UK Department of Earth Sciences, Memorial University of Newfoundland, 300 Prince Philip Drive, St John's, Newfoundland and Labrador, Canada A1B 3X5.
authors.forename: Martin D
authors.initials: MD
authors.lastname: Brasier
mesh_terms: D000818:Animals; D005075:Biological Evolution; D003063:Cnidaria / Q000033:anatomy & histology* / Q000145:classification*; D005580:Fossils / Q000033:anatomy & histology*; D019015:Geologic Sediments; D009523:Newfoundland and Labrador; D010802:Phylogeny; D013045:Species Specificity
keywords: Cnidaria; Ediacaran; Newfoundland; metazoan; muscle