Knowledge of the early evolution of post-Palaeozoic crinoids mainly relies on the well-preserved and abundant material sampled in Triassic Konservat-Lagerstätten such as those from the Anisian Muschelkalk (Middle Triassic) of the Germanic Basin. These crinoid-bearing Lagerstätten have been central to understanding the rapid evolution and diversification of crinoids after the dramatic Permian/Triassic Boundary biological crisis that led the class to near-extinction. The Encrinida are the emblematic crinoids of the Triassic. They are mainly known from rich fossil deposits where their abundant ossicles are at the origin of the extensive crinoidal limestone beds of the German Upper Muschelkalk. So far, they were first represented in the Middle Triassic by the family Dadocrinidae and genus Dadocrinus. In the present work, a new species Dadocrinus montellonis sp. nov., is described based on a well-preserved, almost complete articulated specimen from the Spathian (Lower Triassic) of Nevada (USA). The new species differs from other species of Dadocrinus by its palaeobiogeographic position but also by its earlier stratigraphic occurrence and ancestral morphology. It represents the first reported occurrence of Dadocrinus outside the Germanic Basin prior to the Middle Triassic and also the oldest firm evidence of its presence in the Early Triassic (middle–late Spathian). This discovery sheds new light on the origin of post-Palaeozoic crinoids. It suggests a much wider distribution than commonly assumed for the genus Dadocrinus and implies that the first dadocrinids originated either in the Panthalassa or Tethys oceans, and then dispersed over long distances in a relative short period of time.

Key words: Crinoidea, Articulata, Dadocrinus , Early Triassic, Spathian, Nevada, USA.

Thomas Saucède [thomas.saucede@u-bourgogne.fr; ORCID: https://orcid.org/0000-0001-6056-4447 ], Christopher Smith [christopher.smith@u-bourgogne.fr; ORCID: https://orcid.org/0000-0002-7909-1165], Christophe Durlet [christophe. durlet@u-bourgogne.fr; ORCID: https://orcid.org/0000-0003-2834-1715], Emmanuel Fara [emmanuel.fara@u-bourgogne. fr; ORCID: https://orcid.org/0000-0002-7991-4467], and Arnaud Brayard [arnaud.brayard@u-bourgogne.fr; ORCID: https://orcid.org/0000-0003-1304-6553], Biogéosciences, UMR 6282, CNRS, Université de Bourgogne, 6 boulevard Gabriel, F-21000 Dijon, France. Nicolas Olivier [nicolas.olivier@uca.fr; ORCID: https://orcid.org/0000-0001-6119-3561], Université Clermont Auvergne, CNRS, IRD, Laboratoire Magmas et Volcans, F-63000 Clermont-Ferrand, France. Pierre Guériau [pierre.gueriau@synchrotron-soleil.fr; ORCID: https://orcid.org/0000-0002-7529-3456 ], and Mathieu Thoury [mathieu.thoury@synchrotron-soleil.fr; ORCID: https://orcid.org/0000-0002-8641-3791 ], Université Paris-Saclay, CNRS, ministère de la Culture, UVSQ, MNHN, Institut photonique d’analyse non destructive européen des matériaux anciens UAR3461, 91190 Saint-Aubin, France. Gilles Escarguel [gilles.escarguel@univ-lyon1.fr, ORCID: https://orcid.org/0000-0003-0985-6369 ], Univ Lyon, Université Claude Bernard Lyon 1, CNRS, ENTPE, UMR 5023 LEHNA, F-69622, Villeurbanne, France.