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1 October 2022 Morphometric and Cladistic Analyses of a Theropod Tooth from the Itsuki Formation of the Tetori Group in the Kuzuryu District, Ono City, Fukui Prefecture, Japan
Hirochika Ueda, Yusuke Sakai, Makoto Manabe, Takanobu Tsuihiji, shinji Isaji, Masatoshi Okura
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Abstract

An isolated theropod tooth was found in the Hauterivian–Barremian Itsuki Formation of the Tetori Group in the Kuzuryu district, Ono City, Fukui Prefecture, central Japan. The present specimen, OMFJ V-1, shows a thick lanceolate basal cross-section and small mesial and distal denticles. A cladistic analysis based on the dental characters suggested that OMFJ V-1 be classified as belonging to Allosauroidea or Tyrannosauroidea. Principal component and linear discriminant analyses also suggested that OMFJ V-1 belongs to either of these two theropod clades. The posterior probabilities obtained in the linear discriminant analyses indicated that the confidence of the classification as Allosauroidea is slightly higher than that for Tyrannosauridae. However, because these analyses also supported possibilities of OMFJ V-1 belonging to other theropod clades to lesser extents, its taxonomic referral remains ambiguous. If OMFJ V-1 belongs to Tyrannosauroidea, it would indicate that a medium-sized tyrannosauroid already appeared in central Japan during the Hauterivian–Barremian age. On the other hand, if OMFJ V-1 belongs to Allosauroidea, it would indicate that at least two medium-to-large-sized theropods, allosaurids and tyrannosaurids, lived almost coevally in this region. The third possibility is that OMFJ V-1 belongs to Megaraptora. If such affinities are established, it would represent the oldest record of this clade of theropods.

© by the Palaeontological Society of Japan
Hirochika Ueda, Yusuke Sakai, Makoto Manabe, Takanobu Tsuihiji, shinji Isaji, and Masatoshi Okura "Morphometric and Cladistic Analyses of a Theropod Tooth from the Itsuki Formation of the Tetori Group in the Kuzuryu District, Ono City, Fukui Prefecture, Japan," Paleontological Research 27(1), 51-72, (1 October 2022). https://doi.org/10.2517/PR210002
Received: 11 January 2021; Accepted: 25 July 2021; Published: 1 October 2022
KEYWORDS
cladistic analysis
Itsuki Formation
Japan
morphometric analysis
Tetori Group
theropod tooth
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