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- Title
Redescription of Y inostius major ( Arthrodira: Heterostiidae) from the Lower Devonian of China, and the interrelationships of Brachythoraci.
- Authors
Zhu, You-An; Zhu, Min; Wang, Jun-Qing
- Abstract
Y inosteus major is a heterostiid arthrodire (Placodermi) from the Lower Devonian Jiucheng Formation of Yunnan Province, south-western China. A detailed redescription of this taxon reveals the morphology of neurocranium and visceral side of skull roof. Y inosteus major shows typical heterostiid characters such as anterodorsally positioned small orbits and rod-like anterior lateral plates. Its neurocranium resembles those of advanced eubrachythoracids rather than basal brachythoracids, and provides new morphological aspects in heterostiids. Phylogenetic analysis based on parsimony was conducted using a revised and expanded data matrix. The analysis yields a novel scenario on the brachythoracid interrelationships, which assigns Heterostiidae (including H eterostius ingens and Y inosteus major) as the sister group of D unkleosteus amblyodoratus. The resulting phylogenetic scenario suggests that eubrachythoracids underwent a rapid diversification during the Emsian, representing the placoderm response to the Devonian Nekton Revolution. The instability of the relationships between major eubrachythoracid clades might have a connection to their longer ghost lineages than previous scenarios have implied.
- Subjects
DEVONIAN Period; ARTHRODIRA; GEOLOGICAL formations; PLACODERMI; GEOMORPHOLOGY
- Publication
Zoological Journal of the Linnean Society, 2016, Vol 176, Issue 4, p806
- ISSN
0024-4082
- Publication type
Article
- DOI
10.1111/zoj.12356