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Study of the Tooth Replacement of Chaohusaurus brevifemoralis from the Lower Triassic of Chaohu, Anhui Province

GU Shulun, JIANG Dayong, ZHOU Min

Acta Scientiarum Naturalium Universitatis Pekinensis 2024, 60 (2): 239-248. DOI: 10.13209/j.0479-8023.2024.002

Abstract （37）

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A specimen of Chaohusaurus brevifemoralis (GMPKU-P-3086) from the Lower Triassic in Chaohu City, Anhui Province is examined by using high-resolution CT scan data to create a 3D reconstruction. The reconstructed models include models of teeth, premaxilla, maxilla, and dentary. Through observation and measurement of the model, and comparison with the specimen, the following new features of this basal ichthyosauriformes were found. 1) the implantation is subthecodont based on the presence of a dental groove with shallow sockets at the bottom. 2) the sizes and shapes of the teeth vary periodically and appear as an odd-even alternate pattern. 3) the anterior teeth form a single row, with the replacement tooth setting on the distal position of the functional tooth. 4) Two rows of teeth at the distal parts of the dentary and maxilla are firstly found in Chaohusaurus. The lingual row comprises replacement teeth for the labial row, and each replacement tooth lies disto-lingual of its predecessor. These dental features found in Chaohusaurus brevifemoralis are consistent to that of the Early Triassic ichthyosauriformes, such as Grippia and Utatsusaurus, which might represent a primitive condition of the dental character of ichthyosauriformes and reflect a broad geographical distribution of crunch feeding guild.

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Reanalysis of the Marine Adaptation of the Archosaurian Qianosuchus mixtus from the Middle Triassic of Guizhou, China

Cindy X. SU, ZHOU Min, GU Shulun, Ryosuke Motani, JIANG Dayong

Acta Scientiarum Naturalium Universitatis Pekinensis 2023, 59 (6): 961-969. DOI: 10.13209/j.0479-8023.2023.079

Abstract （358）

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A reanalysis of marine adaptation of Qianosuchus mixtus is given by observing and making measurements to a new specimen. The marine adaptation in non-avian tetrapods follows a pattern of five steps (M1-M5). Comparation of the statistics of Qianosuchus mixtus and other clades leads to the result that Qianosuchus mixtus is placed in M2-3 and not considered to be completely marine. Observation and analysis of the morphology of the new specimen shows that its limbs do not exhibit characters of marine adaptation, yet its body shape and tail are morphologically adapted to undulatory or subundulatory swimming, similar to extant crocodiles and marine iguanas. Comparison with extant crocodiles and other clades suggest that despite having a specialized tail, Qianosuchus mixtus is not capable of swimming at high speed or for long distances. With the information above and reference to the habits of tetrapods in the Panxian Fauna, it is assumed that Qianosuchus mixtus possibly inhabits an intraplatform with islands, and that Qianosuchus mixtus and other upper trophic level predators exhibit complex ecology.

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Characteristics and Source Apportionment of VOCs in Suzhou, China

LI Jiayin, ZHOU Ming, NING Miao, SHI Xurong, YAN Gang, MA Qiang, LU Keding

Acta Scientiarum Naturalium Universitatis Pekinensis 2022, 58 (4): 771-781. DOI: 10.13209/j.0479-8023.2022.051

Abstract （539）

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VOCs concentrations based on offline sampling in Suzhou from July to October 2020 were monitored, and temporal and spatial distribution characteristics, ozone formation potential (OFP) and sources of VOCs were conducted and compared with other studies in China. The results showed that the average concentration of VOCs in Suzhou in the summer is 47.1 nL/L, the average OFP is 334.7 μg/m³, and the aromatic hydrocarbons and oxygenated organics (OVOCs) are important components of VOCs in Suzhou and contribute a lot to ozone generation. The trends of VOCs concentration and composition in Suzhou are similar with those in Shanghai. Positive matrix factorization (PMF) model results showed that six major sources of VOCs in Suzhou are liquefied petroleum gas volatilization sources (20.7%), solvent usage sources (19.5%) and industrial sources (17.5%), followed by other sources, vehicle exhaust emission sources and combustion sources, in which the contribution of liquefied petroleum gas volatilization sources is higher than the general level in Yangtze River Delta. The higher concentration of aromatic hydrocarbons in the Yangtze River Delta is related to the higher contribution of industrial and solvent uses. In general, aromatic hydrocarbons and OVOCs have a greater impact on the atmospheric environment of Suzhou. The main sources are surface coating, gas stations, traffic emission, petrochemical sources and electric heating sources, which should be mainly controlled.

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Redescription of Chaohuperleidus Primus (Actinopterygii, Perleidiformes) from Lower Triassic of Anhui Province, South China

DAI Yanlin, SUN Zuoyu, LU Hao, JIANG Dayong, ZHOU Min

Acta Scientiarum Naturalium Universitatis Pekinensis 2021, 57 (5): 852-864. DOI: 10.13209/j.0479-8023.2021.064

Abstract （882）

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Chaohuperleidus primus has yet to be completely described due to the limit of the original material which were collected from Upper Member of the Nanlinghu Formation (Spathian, Olenekian, Early Triassic) at Majiashan quarry, Chaohu City, Anhui Province. The taxon was redescribed in detail by adding three complete specimens from the type horizons. The generic diagnosis of Chaohuperleidus was revised mainly based on newly recognized anatomical information, of which the following characters ‘the fused parietal and dermopterotic with anterior, middle and posterior pit-lines; the operculum and suboperculum of nearly equal in height with the latter having a large rounded anterior dorsal process’ were possible apomorphies of Chaohuperleidus. The previous taxonomic assignment of the Chaohuperleidus was confirmed, which was similar to the Ladinian (Middle Triassic) genus Perleidus but differed the latter in having more suborbitals, branchiostegal rays and epaxial fin rays besides its possible apomorphies. The skull pattern of the Chaohuperleridus primus was exhaustively reconstructed and was anatomically compared with the Early Triassic taxa which were wrongly classified into the Perleidiformes and some newly described stem neopterygians. The result herein will provide new anatomical evidences for the phylogeny analysis of the stem neopterygians that is open to discuss.

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Late Smithian (Early Triassic) Fish-bearing Concretions from Chaohu Area: Geochemistry and Its Significance

YU Xin, SUN Zuoyu, MENG Qingqiang, JI Cheng, ZHOU Min

Acta Scientiarum Naturalium Universitatis Pekinensis 2021, 57 (2): 225-240. DOI: 10.13209/j.0479-8023.2020.117

Abstract （1072）

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Fish-bearing carbonate concretions are found in the organic-rich shale at the top of Helongshan Formation, Lower Triassic in Chaohu area, Anhui Province. In order to study the formation mechanism and environmental significance of the carbonate concretions, petrography, major and trace elements, carbon and oxygen isotopes and environmental minerals were analyzed for the concretions and surrounding rocks. The 3D-preserved fish fossils and high carbonate content (80%) in the center of concretions indicate that concretions were formed in the early diagenetic stage. Concretions have a concentric zoning structure inside. From the center to the edge, the content of carbonate decreases, the content of siliceous clastic increases and laminae gradually appears, the content of Fe and S elements increases, δ¹³C values increase, δ¹⁸O values decrease, and TOC contents gradually increases, all indicating a concentric growth of concretions. The analysis of the size of framboidal pyrites in the host rock indicates a euxinic environment where concretions were formed. The level of concretions appears 1 m below the Smithian-Spathian boundary (SSB), consistent with the increased burial of organic carbon, rapid positive excursion of δ¹³C (-1.3‰ to 1.9‰) and seawater euxinic event. The concretions have the potential to be regarded as an auxiliary identification marker of SSB in South China.

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Study on Nitrogen Release from Reservoir Sediments and Nitrogen Removal by Aerobic Microorganism

XIE Minzheng, CHEN Qian, DANG Chenyuan, PAN Boyue, AN Rui, WU Zhe, ZHOU Ming

Acta Scientiarum Naturalium Universitatis Pekinensis 2019, 55 (3): 561-570. DOI: 10.13209/j.0479-8023.2019.018

Abstract （765）

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This study focuses on the Danjiangkou reservoir, and investigates the release regulation of total nitrogen, nitrate, nitrite and ammonia from sediments as a function of temperature, perturbation and aeration conditions. Moreover, a simulation reactor was set up to explore the elimination of endogenous nitrogen pollution through high-efficient aerobic denitrification microorganism augmentation. Effects of high-efficient aerobic denitrification microorganisms on the microbial community structure in the sediments was also evaluated by means of high-throughput sequencing technology. The results indicated that increasing temperature could promote the release of nitrate and nitrite from sediments, while inhibiting the release of ammonium. Disturbances of water was beneficial to nitrogen release from sediments, and the nitrogen amount accumulated in the overlying water was proportional to the agitation speed. Concentrations of dissolved oxygen had great effects on the nitrogen release from sediments. It was found that the aeration treatment significantly reduced the release of total nitrogen and nitrite from sediments, and the subsequent accumulation in water. After addition of the a high-efficient aerobic denitrification bacteria Pseudomonas stutzeri (PCN-1) into the simulation reactor, concentrations of all the forms of nitrogen in the reactor increased at first and then decreased. On the 65th day of the experiment, removal rates of total nitrogen and nitrate released from sediments were as high as 75.87% and 79.96% respectively, suggesting effective control of the endogenous nitrogen. The relative abundance of Proteobacteria, Bacteroidetes and Spirochaetes in sediments was significantly increased after PCN-1 addition, so the microbial community structure in the sediments was changed by microbial augmentation treatment with PCN-1 as well.

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Structural and Behavioral Characters of the Early Triassic Ichthyosauriformes from Chaohu, Anhui Province, and Their Implications on the Origin of Ichthyopterygia

LU Hao, JI Cheng, NI Peigang, ZHOU Min, FU Wanlu

Acta Scientiarum Naturalium Universitatis Pekinensis 2016, 52 (2): 234-240. DOI: 10.13209/j.0479-8023.2015.115

Abstract （1351）

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Ichthyosaurs, firstly appeared at the end of the Early Triassic. The previously reported Ichthyosaurs show very high level of adaptability to life in water, and their osteology shows structural characters that are fully adapted to life in water without any terrestrial characters that can relate them to their terrestrial ancestor. Two specimens are studied, one belonging to Cartorhynchus and the other to Chaohusaurus with embryos found from the Lower Triassic (Olenekian) of Chaohu, Anhui Province, South China. Based on studies of the number of presacral vertebra (i.e. 31), the ratio of snout length to skull length (i.e. 0.35), the ratio of forelimb length to presacral vertebra length (i.e. 0.45), and comparisons of these measurements and morphological characters with the derived Ichthyosaurs, Cartorhynchus is considered to be primitive in structural features and to have an amphibianlike habit. Combined with the analyses of the embryo-bearing specimens of the Early Triassic Chaohusaurus and the Jurassic Stenopterygius, Chaohusaurus appears more derives than Cartorhynchus in body structural characters and is fully adapted to life in water; however, Chaohusaurus retained a head-first birth posture when giving birth to offsprings. Therefore, during the evolution of Ichthyosaurs from terrestrial ancestors to marine types, the adaptive structural characters (such as flipper, and elongate snout) and the adaptive behavioral characters (such as the mode of reproduction) might have evolved in different tempo, and the former changed earlier.

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Comparison of the Forefin of Chaohusaurus and Its Taxonomy Meaning, Early Triassic, Anhui Province

ZHOU Min

Acta Scientiarum Naturalium Universitatis Pekinensis 2016, 52 (2): 227-233. DOI: 10.13209/j.0479-8023.2015.077

Abstract （1257）

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Due to the low number and bad preserved condition of the specimens, the anatomical features of Chaohusaurus have not been described in detail. As a result, there is a controversy about the membership of this genus. Based on some new specimens housed in the Geological Museum of Peking University, there are two styles of the forefins compared with the holotype, with differences in skeleton morphology and the mesopodial ossification. The cluster analysis of those specimens shows that there are two groups. Measurements of the forefins suggests that there are two trendlines, so the conclusion that Chensaurus xiaoxianensis and Chensaurus faciles are junior synonyms of Chaohusaurus geishanensis is not appropriate. There are at least two species of Chaohusaurus in Chaohu. Clarifing the diversity of this genus is of significance to the comparison of the Early Triassic ichthyosaurs in the world and the study of the early evolution of basal ichthyosaurs.

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Re-recognition of Deep Carbonate Dissolution Based on the Observation of in-situ Simulation Experiment

YANG Yunkun,LIU Bo,QIN Shan,LUO Ping,ZHANG Shanming,ZHOU Minghui,SHI Kaibo,TIAN Yongjing

Acta Scientiarum Naturalium Universitatis Pekinensis

Abstract （702）

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A set of new carbonate dissolution in-situ experiments was designed to simulate the real burying process and to test its affection on fluid-rock reaction. By adoption DAC, the experimental process was controlled by the heater according to the paleothermal gradient of NE Sichuan. Experiment results indicate that limestone show precipitation with the increase of temperature and pressure. Dolomite is more stable than limestone in the whole experimental process, which shows a quite different result from the standpoint that dolomite is more dissoluble than limestone in high temperature and high pressure conditions. The “dissolution window” was not observed in the whole experimental process. The experimental researches may provide some new perspectives to the recognition of the formation and preservation mechanism for the deep carbonate reservoir.

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Determination of Atmospheric Boundary Layer Height in Unstable Conditions over the Middle Tibetan Plateau

SONG Xingzhuo,ZHANG Hongsheng,LIU Xinjian,FAN Shaohua,LIU Huizhi,HU Fei,LI Shiming,ZHOU Mingyu,BIAN Lingen,XU Xiangde

Acta Scientiarum Naturalium Universitatis Pekinensis

Abstract （737）

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The atmospheric boundary layer (ABL) height z_i in unstable condition was analyzed using turbulence data from Damxung observational station, which was one of the ABL observational stations in the second Tibet Plateau Experiment (TIPEX) in 1998. Together with the observational vertical profiles of temperatures, the authors studied the diurnal and seasonal evolution characteristics of the ABL over the Tibet Plateau, analyzed both differences and similarities of the ABL between dry and wet seasons, and explored the terrain influence on the ABL height. The results show that the ABL over Tibet Plateau has the characteristics of development and lasting over a longer time.

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The Characteristics of Dissipation Rates of Turbulent Variance over Damxung Area in the TIbetan Plateau

LI Fuyu,ZHANG Hongsheng,LI Shiming,ZHOU Mingyu,CHEN Jiayi,XU Xiangde,LIU Huizhi,HU Fei

Acta Scientiarum Naturalium Universitatis Pekinensis

Abstract （785）

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The turbulent data obtained from Damxung site during TIPEX in 1998 were used to study the characteristics of dissipation rates of turbulent kinetic energy, temperature variance and humidity variance in the middle area of Tibetan Plateau. The results indicate that the dimensionless dissipation rates of turbulent energy are 20% less than the energy produced by velocity shear, and the dimensionless temperature and humidity variances are also 20% less than the variances produced by temperature and humidity gradients. These deficits appear to increase with the increasing of the absolute stability parameter. Moreover, the effects of turbulent transportation and pressure variance, which are related with the stability parameter, persist throughout the whole stability region. The differences between these results and some previous studies show the underlying-surface-dependant characteristics of the dissipation rates of turbulent energy, temperature variance and humidity variance.

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