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TitreThe elusive origin of Chiosella timorensis (Conodonts Triassic)
AuteurGoudemand, N; Orchard, M J; Buchers, H; Jenks, J
SourceGEOBIOS vol. 45, 2012 p. 199-207,
Séries alt.Secteur des sciences de la Terre, Contribution externe 20100437
Documentpublication en série
Mediapapier; en ligne; numérique
Lat/Long OENS-118.5000 -118.0000 40.7500 40.2500
SujetsTrias inférieur; Trias moyen; biostratigraphie; stratigraphie paléontologique; fossiles; assemblages fossiles; fossiles stratigraphiques; paléontologie; stratigraphie; Mésozoïque; Trias
Illustrationslocation maps; plates; plots
Programmebassins sédimentaires du Yukon, GEM : La géocartographie de l'énergie et des minéraux
Résumé(disponible en anglais seulement)
The First Appearance Datum (FAD) of the conodont Chiosella timorensis has been recently proposed as an index for the worldwide recognition of the Olenekian-Anisian Boundary (OAB, Early-Middle Triassic boundary). We here report the co-occurrence of C. timorensis with the ammonoids Neopopanoceras haugi (Hyatt and Smith), Keyserlingites pacificus (Hyatt and Smith), Subhungarites yatesi (Hyatt and Smith) and Pseudacrochordiceras inyoense (Smith), which are diagnostic of the late Spathian Haugi Zone. This shows that the previously published first occurrences of C. timorensis were still too poorly constrained, and it questions the adequacy of its FAD as a marker of the OAB. It challenges the significance of some observed lower stratigraphic occurrences of C. gondolelloides compared with C. timorensis. We revise the current criterion for the taxonomic separation of these two species and define a new Chiosella species (left in open nomenclature). The origin of Chiosella timorensis remains unknown but multi-element analyses suggest an affinity with the late Olenekian Neogondolella ex gr. regalis. Our reassessment of the material from the most important OAB sections (Desli Caira, Romania and Guandao, China) allows us to propose a new and more reliable biochronological scheme based on conodont maximal associations for the OAB.