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Motani R.,University of California at Davis | Jiang D.-Y.,Laboratory of Orogenic Belt and Crustal Evolution | Xue Y.-F.,Laboratory of Orogenic Belt and Crustal Evolution | Tintori A.,University of Milan
Proceedings of the Royal Society B: Biological Sciences | Year: 2015

The evolutionary history of sexual selection in the geologic past is poorlydocumented based on quantification, largely because of difficulty in sexingfossil specimens. Even such essential ecological parameters as adult sex ratio(ASR) and sexual size dimorphism (SSD) are rarely quantified, despite theirimplications for sexual selection. To enable their estimation, we propose amethod for unbiased sex identification based on sexual shape dimorphism,using size-independent principal components of phenotypic data.We appliedthe method to test sexual selection in Keichousaurus hui, a Middle Triassic(about 237 Ma) sauropterygian with an unusually large sample size for afossil reptile. Keichousaurus hui exhibited SSD biased towards males, as inthe majority of extant reptiles, to a minor degree (sexual dimorphism index20.087). The ASR is about 60% females, suggesting higher mortality ofmales over females. Both values support sexual selection of males in thisspecies. The method may be applied to other fossil species. We also used theGompertz allometric equation to study the sexual shape dimorphism ofK. hui and found that two sexes had largely homogeneous phenotypes atbirth except in the humeral width, contrary to previous suggestions derivedfrom the standard allometric equation. © 2015 The Author(s) Published by the Royal Society. All rights reserved. Source


Ji C.,CAS Nanjing Institute of Geology and Palaeontology | Zhang C.,CAS Nanjing Institute of Geology and Palaeontology | Jiang D.-Y.,Laboratory of Orogenic Belt and Crustal Evolution | Bucher H.,University of Zurich | And 2 more authors.
Palaeoworld | Year: 2015

Here we described a series of ammonoid specimens from the Early Triassic of Chaohu, South China and recognized the occurrence of Procolumbites for the first time in this area. The Procolumbites layer is about one meter above the first appearance of Chaohusaurus, indicating that the oldest Chaohusaurus is within the Procolumbites Zone of middle Spathian age. This new age constrain is significantly older than the previously suggested Subcolumbites Zone assignment (early late Spathian). To date, Chaohusaurus is the oldest known ichthyopterygian. © 2014 Nanjing Institute of Geology and Palaeontology, CAS. Source


Tintori A.,University of Milan | Huang J.-D.,Anhui Geological Museum | Jiang D.A.-Y.,Laboratory of Orogenic Belt and Crustal Evolution | Jiang D.A.-Y.,Peking University | And 5 more authors.
Rivista Italiana di Paleontologia e Stratigrafia | Year: 2014

A new species of Sauricbthys, S. majiasbanensis, is described. It comes from a series of marine vertebrate-bearing beds of the upper member of the Nanlinghu Formation outcropping in the large quarry at the top of Majiashan (Majia Hill) near Chaohu (Hefei City, Anhui Province, China). Its age is Middle Spathian (Olenekian, Early Triassic). This new species deeply differs from the several pre-Spathian species of Sauricbthys mainly for having only two longitudinal scale rows together with a reduced grid-like structure for the neural elements in the vertebral column. Further derived characters are in the endoskeleton of the dorsal and anal fin, where radiais articulate only to anterior lepidotrichia, the posterior ones being supported by the first scale from the caudal pedicle mid-dorsal and mid-ventral rows, deeply imbedded in the body. In addition, the haemal spines of the caudal region are much enlarged and reversed, with their distal parts pointing forwards. Though the skull is lacking, postcranial characters are enough to justify the erection of a new species. This new Saurichthys species, together with other few actinopterygians, can be considered as the oldest assemblage of the Triassic Middle Fish Fauna, which bloomed probably in the early Anisian and widespread especially all over the Tethys for the Middle Triassic and at least the Carnian in the Late Triassic. This new fish assemblage, together with some of the oldest marine reptiles, is considered as the beginning of the actual Triassic recovery among marine vertebrates. Source

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