Alexandre Hassanin, GÃraldine Veron, Anne Ropiquet, Bettine Jansen van Vuuren, Alexis LÃcu, Steven M. Goodman, Jibran Haider &Trung Thanh Nguyen (2021)
Evolutionary history of Carnivora (Mammalia, Laurasiatheria) inferred from mitochondrial genomes.
PLoS ONE
doi:
https://doi.org/10.1371/journal.pone.0240770https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0240770The order Carnivora, which currently includes 296 species classified into 16 families, is distributed across all continents. The phylogeny and the timing of diversification of members of the order are still a matter of debate. Here, complete mitochondrial genomes were analysed to reconstruct the phylogenetic relationships and to estimate divergence times among species of Carnivora. We assembled 51 new mitogenomes from 13 families, and aligned them with available mitogenomes by selecting only those showing more than 1% of nucleotide divergence and excluding those suspected to be of low-quality or from misidentified taxa. Our final alignment included 220 taxa representing 2,442 mitogenomes. Our analyses led to a robust resolution of suprafamilial and intrafamilial relationships. We identified 21 fossil calibration points to estimate a molecular timescale for carnivorans. According to our divergence time estimates, crown carnivorans appeared during or just after the Early Eocene Climatic Optimum; all major groups of Caniformia (Cynoidea/Arctoidea; Ursidae; Musteloidea/Pinnipedia) diverged from each other during the Eocene, while all major groups of Feliformia (Nandiniidae; Feloidea; Viverroidea) diversified more recently during the Oligocene, with a basal divergence of Nandinia at the Eocene/Oligocene transition; intrafamilial divergences occurred during the Miocene, except for the Procyonidae, as Potos separated from other genera during the Oligocene.
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Laosuchus hun sp. nov.
Jun Liu & Jianye Chen (2021)
The tetrapod fauna of the upper Permian Naobaogou Formation of China: 7. Laosuchus hun sp. nov. (Chroniosuchia) and interrelationships of chroniosuchians.
Journal of Systematic Palaeontology (advance online publication)
DOI: 10.1080/14772019.2021.1873435
https://www.tandfonline.com/doi/full/10.1080/14772019.2021.1873435
Chroniosuchians were the only clade of non-amniotic reptiliomorphs that survived into the Triassic. Recent discoveries have increased their species and anatomical diversity and expanded their distribution in time and space. Most species were represented only by osteoderms, and complete or articulated remains are rare. Here we report a partial skull with a mandible and associated postcranial skeleton from the Naobaogou Formation in the Daqingshan, Nei Mongol, China. It is referred to Laosuchus based on the absence of a preorbital fenestra, the presence of a well-developed transverse flange of the pterygoid that contacts the maxilla, an internal crest on and above the dorsal side of the palate (vomer, ectopterygoid and pterygoid), a shallow otic notch formed by the tabular horn and the posterior part of the squamosal, a thin and high ventromedial ridge on the parasphenoid; the surangular dorsal surface forming a fossa for the insertion of the external adductors, the maxilla and quadratojugal separated by the jugal, and a jugal with a ventral (alary) process bordering the subtemporal fenestra. A new species, L. hun, is established based on its palatal dentition that is reduced, with but a few denticles on the vomer and pterygoid, and an irregular posterior cheek margin. Laosuchus can be referred to Chroniosuchidae based on cranial features, and the divergence of the Chroniosuchidae and Bystrowianidae is confirmed in this study. New findings reinforce the hypothesis of the migration route from North China to Laos in the late Permian.
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Zhixin Ma, Shixue Hu, Xiting Liu, Changyong Zhou, Wen Wen, Qiyue Zhang, Jinyuan Huang Â& Xiao Min (2021)
The link between exceptional fossil preservation and palaeoâredox conditions in the Middle Triassic Luoping Biota from South China.
Geological Journal (advance online publication)
doi:
https://doi.org/10.1002/gj.4106https://onlinelibrary.wiley.com/doi/10.1002/gj.4106The Luoping Biota represents of the recovery of marine ecosystems after the Permian-Triassic Mass Extinction. To better understand the palaeoenvironmental background of the Luoping Biota, sedimentary analysis and multiâgeochemical proxies (Mo, U, V, V/Cr, MoEF, UEF, and VEF) were assessed in Member II of the Middle Triassic Guanling Formation of the Xiangdongpo section in Luoping County, Yunnan Province. According to the facies characteristics and redoxâsensitive elemental proxies, in combination with macrofossil and bioturbation evidence, five intervals (I, II, III, IV, and V) were recognized. The exceptional preservation of the fossils is related to two anoxic intervals (II and IV) sandwiched by three suboxic intervals (I, III, and V). Based on this study and regional correlation, it is concluded that anoxia in the waterâcolumn increased the preservation potential of macrofauna fossils and inhibited the survival of traceâmaking organisms. In addition, microbial mats could produce local anoxic and restricted microâenvironments, preventing the disarticulation of the carcasses by water turbulence. Therefore, we demonstrate that anoxic conditions played a key role in the exceptional fossil preservation of the Luoping Biota.
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Amniotes, a clade of terrestrial vertebrates, which includes all of the descendants of the last common ancestor of the reptiles (including dinosaurs and birds) and mammals, is one of the most successful group of animals on our planet. In addition to having an egg equipped with an amnion, an adaptation to lay eggs on land, amniotes possess a number of other major morphological characteristics. Chief among them is the amniote skull, which can be classified into several major types distinguished by the presence and number of temporal fenestrae (windows) in the posterior part. Amniotes evolved from ancestors who possessed a skull composed of a complex mosaic of small bones separated by sutures. Changes in skull composition underlie much of the large-scale evolution of amniotes with many lineages showing a trend in reduction of cranial elements known as the "Williston's Law." The skull of amniotes is also arranged into a set of modules of closely co-evolving bones as revealed by modularity and integration tests. One of the most consistently recovered and at the same time most versatile modules is the âface,â anatomically defined as the anterior portion of the head. The faces of amniotes display extraordinary amount of variation, with many adaptive radiations showing parallel tendencies in facial scaling, e.g., changes in length or width. This review explores the natural history of the amniote face and discusses how a better understanding of its anatomy and developmental biology helps to explain the outstanding scale of adaptive facial diversity. We propose a model for facial evolution in the amniotes, based on the differential rate of cranial neural crest cell proliferation and the timing of their skeletal differentiation.
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