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LÃa Terray, Olivia Plateau, Anick Abourachid, Christine BÃhmer, Arnaud DelaprÃ, Xavier de la Bernardie & RaphaÃl Cornette (2020)
Modularity of the Neck in Birds (Aves).
Evolutionary Biology (advance online publication)
doi:
https://doi.org/10.1007/s11692-020-09495-whttps://link.springer.com/article/10.1007/s11692-020-09495-wThe neck connects the head and the trunk and is the key structure allowing all movements of the head. The neck morphology of birds is the most variable among living tetrapods, including significant differences in the number and shape of the cervical vertebrae. Despite these differences, according to the literature, three morphofunctional regions (i.e., modules) have been identified along the neck. However, this regionalization has not been quantitatively tested through a geometric morphometric approach applied to the cervical vertebrae. Based on the examination of 187 cervical vertebrae belonging to 16 species with various ecologies, we revealed a common modular structure of the neck using 3D surface geometric morphometrics. We adopted an approach without a priori clustering to identify modules along the neck. The phylogenetic influence on each module was tested. Then, each module was digitally reconstructed as a 3D vertebral model, and postural characteristics were studied. We characterized 9 modules: 7 are transpecific, being shared by at least 2 and up to 15 species. Two modules are specific to species with particularly long necks. The modularity pattern appears to be tightly linked to morphofunctional aspects and partially to phylogeny. In contrast, feeding ecology seems to be more closely related to the chaining of modules (the neck) than to the modules themselves. A study of postural properties revealed that each modular unit exhibits a characteristic curvature. Overall, the modular structure of the neck corresponds to the three traditional functional regions. However, the results also revealed unexpected pattern complexity, including subdivisions within these regions. The study of the patterns of modularity is therefore a relevant approach for challenging the three-functional-region hypothesis and allowed us to identify the structure of the diversity of the necks of birds.
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Xiangdong Zhao, Daran Zheng, Guwei Xie, Hugh C. Jenkyns, Chengguo Guan, Yanan Fang, Jing He, Xiaoqi Yuan, Naihua Xue, He Wang, Sha Li, Edmund A. Jarzembowski, Haichun Zhang & Bo Wang (2020)
Recovery of lacustrine ecosystems after the end-Permian mass extinction.
Geology (advance online publication)
doi:
https://doi.org/10.1130/G47502.1https://pubs.geoscienceworld.org/gsa/geology/article-abstract/doi/10.1130/G47502.1/583387/Recovery-of-lacustrine-ecosystems-after-the-end
The end-Permian mass extinction (EPME; ca. 252 Ma) led to profound changes in lacustrine ecosystems. However, whether or not post-extinction recovery of lacustrine ecosystems was delayed has remained uncertain, due to the apparent rarity of Early and Middle Triassic deep perennial lakes. Here we report on mid-Middle Triassic lacustrine organic-rich shales with abundant fossils and tuff interlayers in the Ordos Basin of China, dated to ca. 242 Ma (around the Anisian-Ladinian boundary of the Middle Triassic). The organic-rich sediments record the earliest known appearance, after the mass extinction, of a deep perennial lake that developed at least 5 m.y. earlier than the globally distributed lacustrine shales and mudstones dated as Late Triassic. The fossil assemblage in the organic-rich sediments is diverse and includes plants, notostracans, ostracods, insects, fishes, and fish coprolites, and thus documents a Mesozoic-type, trophically multileveled lacustrine ecosystem. The results reveal the earliest known complex lacustrine ecosystem after the EPME and suggest that Triassic lacustrine ecosystems took at most 10 m.y. to recover fully, which is consistent with the termination of the "coal gap" that signifies substantial restoration of peat-forming forests.