Guanling Biota: A Marker of Triassic Biotic Recovery from the end-Permian Extinction in the Ancient Guizhou Sea

After a slow recovery from the end-Permian extinction during the Early Triassic and rapid radiation in the Middle Triassic, evolution of organisms reached a new peak phase in the Late Triassic. The Guanling Biota from the Wayao Member （conodont Paragondolella polygnathiformis Zone）, Falang Formation, Xinpu, Guanling County, Guizhou Province, southwestern China corresponds to this peak that marks the full recovery from the end-Permian extinction of marine ecosystems. The biota is of high diversity, containing well preserved and completely articulated skeletons of vertebrates comprising marine reptiles, fishes, and invertebrates including crinoids, ammonites, bivalves, and other fossils, and is one of the best examples of marine ecosystem records in life history. The fossil marine reptiles and crinoids are most significant in this biota, especially the marine reptiles, which provide an important link between the Triassic Pacific and Tethys, and between Triassic basal forms and the Jurassic-Cretaceous marine top predators. The most remarkable fossils are the large completely articulated ichthyosaur skeletons up to and more than 10 m, and the first recorded thalattosaurs and placodonts in China. Following our review, of the 17 named reptilian taxa the eight listed here are considered to be valid： three ichthyosaurs （Qianichthyosaurus zhoui Li, 1999; Guizhouichthyosaurus tangae Cao and Luo in Yin et al., 2000, Guanlingsaurus liangae Yin in Yin et al., 2000）, three thalattosaurs （Anshunsaurus huangguoshuensis Liu, 1999, Xinpusaurus suni Yin in Yin et al., 2000, Xinpusaurus kohi Jiang et al., 2004）, and two placodonts （Sinocyamodus xinpuensis Li, 2000, Psephochelys polyosteoderma Li and Rieppel, 2002）. Mixosaurus guanlingensis Cao in Yin et al., 2000 might be a junior synonym of Qianichthyosaurus zhoui Li, 1999, and Cymbospondylus asiaticus Li and You, 2002 and Panjiangsaurus epicharis Chen and Cheng, 2003 might be junior synonyms of Guizhouichthyosaurus tangae Cao and Luo in Yin et al., 2000. It needs to re-describe the holotypes after a complete preparation for clarifying the taxonomic status of Typicusichthyosaurus tsaihuae Yu in Yin et al., 2000, Xinpusaurus bamaolinensis Cheng, 2003, Neosinosaurus hoangi （Zhou in Yin et al., 2000）, Wayaosaurus geei Zhou in Yin et al., 2000, Wayaosaurus bellus Zhou in Yin et al., 2000 and Placochelys ？ minutus Yin and Luo in Yin et al., 2000.

Guanling Biota: A Rare Biota in Sea Early Late Triassic

Guanling biota has been found at the bottom of Wayao Formation of Upper Triassic (Carnic stage) near Xinpu town, Guanling County, Guizhou Province, China. There are a lot of crinoids and marine reptiles, which is a characteristic of Guanling biota, including ammonites, bivalve, brachiopod, fish, conodont and plant. These fossils are featured not only with the large quantity, but also with their extraordinary perfect forms. This paper explores the meaning, geological background, present situation of study and scientific significance of Guanling biota.

Biostratigraphy of Triassic Marine Reptiles in Southwest Guizhou and Its Adjacent Area

This paper briefly reviews the Triassic marine reptile fossils in Guizhou Province, especially the fossils that have been recently found in the Guanling area. Based on three sections at Guanling and Xingyi, Guizhou Province and Luoping, Yunnan Province, four horizons with vertebrate fossils are recognized in the Middle and Upper Triassic of this area; They are from bottom to top: Member I and Member II of the Guanling Formation, and the Zhuganpo Member and the Wayao Member of the Falang Formation.

Dawazisaurus Brevis, A New Eosauropterygian From the Middle Triassic of Yunnan, China

Dawazisaurus brevis（gen. et sp. nov.） is a newly discovered Triassic marine reptile, represented by a complete skeleton from Member II of the Guanling Formation of Luoping, Yunnan Province, China. This paper aims to（1） present a thorough description of the species,（2） make a detailed comparison to demonstrate if the species can be referred to any known sauropterygian taxa, and（3） conduct phylogenetic analyses to establish the internal relationships of the species with other sauropterygians. In addition, the discovery of Dawazisaurus provides a chance not only to test the phylogenetic patterns of the Sauropterygia obtained by previous studies but also to evaluate the previous hypotheses on the origin of the sauropterygian groups at different levels. D. brevis is an eosauropterygian, characterized by a unique combination of derived features such as a pair of large nasals joining in the formation of the internarial septum, a short trunk with 16 dorsal vertebrae; the zygapophyses of the trunk vertebrae very small or weakly developed; the posterior margin of the skull roof deeply V-shaped, and an ossified distal carpal 5. Phylogenetic analysis indicates that D. brevis appears to be more closely related to the Nothosauroidea than the Pistosauroidea within the Eosauropterygia.

Spatiotemporal Evolution of Ecological Quality in Typical Karst Ecologically Fragile Areas Based on Remote Sensing Ecological Indexes

Fast and effective remote sensing monitoring is an important means for analyzing the spatio-temporal changes in ecological quality in fragile karst regions.This study focuses on Guanling Autonomous County,a national-level demonstration county for comprehensive desertification control.Based on Landsat TM/OLI remote sensing image data from 2005,2010,2015,and 2020,remote sensing ecological indices were used to analyze the spatio-temporal changes in ecological quality in Guanling Autonomous County from 2005 to 2020.The results show that:①the variance contribution rates of the first principal component for the four periods were 66.31%,71.59%,63.18%,and 75.24%,indicating that PC1 integrated most of the characteristics of the four indices,making the RSEI suitable for evaluating ecological quality in karst mountain areas;②the remote sensing ecological index grades have been increasing year by year,with an overall trend of improving ecological quality.The area of higher-grade ecological quality has increased spatially,while fragmented patches have gradually decreased,becoming more concentrated in the low-altitude areas in the northwest and east,and there is a trend of expansion towards higher-altitude areas;③the ecological environment quality in most areas has improved,with the improvement in RSEI spatio-temporal variation becoming more noticeable with increasing slope.Areas of higher-grade quality appeared in 2010,and the range of higher-grade quality expanded with increasing slope.

A conodont-based Middle Triassic age assignment for the Luoping Biota of Yunnan, China

The Luoping Biota consists of abundant and well-preserved marine fishes, reptiles, invertebrates, and plants. It occurs in the Middle Triassic Guanling Formation in Daaozi Village of Luoping County, Yun-nan Province, China. Based on conodonts, the Luoping Biota is determined to lie within the Nicoraella kockeli Zone, which is assigned to the Pelsonian substage of the Anisian.

A New Eosauropterygian(Diapsida:Sauropterygia) from the Middle Triassic of Luoping,Yunnan Province

A new eosauropterygian, Largocephalosaurus polycarpon gen. et sp. nov., was described based on a skeleton from the Middle Triassic of Luoping （罗平）, Ynnnan （云南） Province, southwestern China. The new taxon is characterized by a big skull, paired frontal, laterally expanded upper temporal fossa, anterior process of squamosal entering orbit, robust teeth with basally expanded crown and blunt tip, short cervical region, distinctly elongated transverse process of the dorsal vertebrae, short and broad dorsal ribs, stout gastralia, scapula with distinctly posterodorsally extending blade, distinctly robust humerus, eleven carpal ossifications, and a manual fomula of 2-3-4-5-5. A phylogenetic analysis suggests that Largocephalosaurus is the basal-most member of a clade including Wumengosaurus, European pachypleurosaurs, and Nothosauroidea.