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Chaohusaurus chaoxianensis, valid ichthyopterygian species from Early Triassic of China
A new online paper:
Ryosuke Motani, Da-Yong Jiang, Andrea Tintori, Olivier Rieppel,
Guan-Bao Chen & Hailu You
Status of Chaohusaurus chaoxianensis (Chen, 1985)
Journal of Vertebrate Paleontology (advance online publication)
The Early Triassic ichthyopterygian Chaohusaurus chaoxianensis was
previously known from juvenile specimens only. It was considered to
represent immature forms of C. geishanensis, which was based on a
single adult specimen, because allometric regression lines of the
forelimb skeletons suggested that the two name groups fitted along a
single growth trajectory. The sample size for the analysis, however,
was small (n = 5). We collected new specimens of Chaohusaurus from
Majiashan, Chaohu City, Anhui Province, China, through field
excavations that started in 2010. New specimens included an immature
individual whose forelimb resembled that of mature C. geishanensis, as
well as a large adult individual whose forelimb retained the
characteristics of immature C. chaoxianensis. Therefore, C.
chaoxianensis is not the juvenile of C. geishanensis. With the
addition of the new specimens, two growth trajectories are now clearly
detected on allometric regression plots (n = 15). The two species are
unambiguously distinguished from each other based on a suite of
discrete characters that are diagnostic to each species, as well as
statistical analyses of forelimb measurements. It is unlikely that the
two forms represent the genders of a single species given that C.
geishanensis is vastly outnumbered by C. chaoxianensis and completely
lacking in major fossiliferous rock layers. Therefore, C.
chaoxianensis should be resurrected as a valid species.