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The elusive origin of Chiosella timorensis (conodonts, Triassic)


Goudemand, N; Orchard, M J; Bucher, H; Jenks, J (2012). The elusive origin of Chiosella timorensis (conodonts, Triassic). Geobios, 45(2):199-207.

Abstract

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.

Abstract

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.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Paleontological Institute and Museum
Dewey Decimal Classification:560 Fossils & prehistoric life
Language:English
Date:2012
Deposited On:26 Jan 2012 09:04
Last Modified:26 Jan 2017 08:50
Publisher:Elsevier
ISSN:0016-6995
Publisher DOI:https://doi.org/10.1016/j.geobios.2011.06.001

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