分类： 生物学 >> 动物学 提交时间： 2022-06-07 合作期刊: 《古脊椎动物学报》
摘要： Nothosaurus luopingensis n. sp. from Member II of the Guanling Formation (Anisian, Middle Triassic) of Luoping, Yunnan, China is described based on a specimen comprising the skull and most of the postcranial skeleton. The specimen is assigned to Nothosaurus of Eosauropterygia as suggested by a series of skull characters, such as the maxillary tooth row extending posteriorly beyond the level of the anterior margin of the upper temporal fenestra, the longitudinal diameter of the upper temporal fenestra is more than twice as long as that of the orbit, and the presence of maxillary fangs. Compared with Lariosaurus, the following morphological features of the pectoral girdle and the limbs also support the assignment of the specimen to Nothosaurus, i.e., the clavicles with expanded anterolateral corners, the characteristically curved humerus with a straight preaxial angle and a postaxial concavity, the distinct deltopectoral crest on the proximal part of the humerus, no hyperphalangy in the manus, and the absence of pachyostosis in the vertebrae and ribs. On the other hand, the specimen possesses some postcranial features that were previously considered to occur mainly in Lariosaurus, such as there being more than three ossifications in the carpus, having four sacral ribs, and an interclavicle without any trace of a posterior stem. These postcranial characters may no longer be used as the diagnostic features of Lariosaurus. N. luopingensis is distinguished from other Nothosaurus species by a unique combination of derived characters, including that the jugal enters the orbit, the nasals are separated, the posterior end of the frontal is bifurcate, pedal digits V and IV are long and subequal in length, and the ungula phalanx is stout. Our phylogenetic analysis reconfirms the monophyly of Nothosaurus and suggest that N. luopingensis is the sister group of N. yangjuanensis within the genus.
分类： 生物学 >> 动物学 提交时间： 2022-04-16 合作期刊: 《古脊椎动物学报》
摘要： Platybelodon is the predominant proboscidean of northern China’s Middle Miocene. However, the cranial and cheek tooth morphologies are not clearly diagnosed. In particular, the differential diagnoses between Platybelodon and Gomphotherium have not been comprehensively examined. Here we restudied the cranium previously identified as Gomphotherium shensiense. The upper tusks lack an enamel band, the rostrum is long and narrow, the facial part is rostrally positioned, and a large “prenasal slope” is present. These characters are distinct from those of any species of Gomphotherium, but fit well with some primitive species of Platybelodon, i.e., P. tongxinensis and P. danovi. The molars are also close to the type specimen of P. tongxinensis in the tetralophodont M3 with mesiodistally wide interlophs, curved outline, and a tendency of cementodonty. In this article, we synonymized Gomphotherium shensiense with P. tongxinensis. Moreover, we recognized a new species, Platybelodon tetralophus, from the P. grangeri material collected by the AMHN expedition in Tunggur region. Platybelodon tetralophus differs from P. grangeri and the other species in the tetralophodont M2 and m2, representing the most derived species within Platybelodon. It has only occurred in the uppermost horizon of the Tunggur Formation, i.e., the Tamuqin Fauna (Platybelodon Quarry and Wolf Camp Quarry of AMHN). This work is a comprehensive amending of the genus Platybelodon.
分类： 生物学 >> 动物学 提交时间： 2017-11-07 合作期刊: 《古脊椎动物学报》
摘要： Eggs or embryos have been reported in various groups of fossil reptiles, where viviparity is a common mode of reproduction in aquatic taxa such as the ichthyopterygians, some groups of sauropterygians, mosasauroids, some taxa of choristoderans and certain protorosaurs. Here, we describe a complete embryo of a marine protorosaur, based on a well-preserved, curled-up skeleton. The new discovery is referred to a taxon closely related to the remarkable long-necked Dinocephalosaurus. It further confirmed viviparity in an archosauromorph group and indicates an increasing taxonomic diversity not only within this group, but of Triassic marine reptiles in general.
分类： 地球科学 >> 地质学 提交时间： 2017-08-08 合作期刊: 《古脊椎动物学报》
摘要： Eggs or embryos have been reported in various groups of fossil reptiles, where viviparity is a common mode of reproduction in aquatic taxa such as the ichthyopterygians, some groups of sauropterygians, mosasauroids, some taxa of choristoderans and certain protorosaurs.Here, we describe a complete embryo of a marine protorosaur, based on a well-preserved, curledup skeleton. The new discovery is referred to a taxon closely related to the remarkable longnecked Dinocephalosaurus. It further confirmed viviparity in an archosauromorph group and indicates an increasing taxonomic diversity not only within this group, but of Triassic marine reptiles in general.
分类： 生物学 >> 动物学 提交时间： 2023-09-20 合作期刊: 《古脊椎动物学报》
摘要： 间型三棱齿象(Trilophodon connexus Hopwood, 1935)长期以来被认为是中国嵌齿象属 (Gomphotherium)的一个代表种。然而，由于其下颌联合部与下门齿的形态未知，这一归入 存疑。重新研究了来自新疆准噶尔盆地北缘乌伦古河地区哈拉玛盖组的一件此前归为陕西嵌齿象相似种(Gomphotherium cf. G. shensiensis)的下颌。该下颌联合部伸长，呈深槽状， 下门齿缺失，因此确定可归入豕棱齿象科(Choerolophodontidae)。进一步将间型三棱齿象 的正型标本与其相比较，两者颊齿的关键特征完全一致，包括：高度丘型化，m3伸长， 具有四脊，上下颊齿第二脊人字型(chevron)很弱，第二脊中附锥与前中心小尖不愈合， 釉质褶皱、齿谷中小锥及白垩质发育弱或缺失。因此，间型三棱齿象事实上是一种豕棱齿 象类而非嵌齿象。综上所述，暂将其改定为间型豕棱齿象 (Choerolophodon connexus (Hopwood, 1935))。同时，以上特征与北美的索普颌门齿象(Gnathabelodon thorpei)比较接 近。此外，在颌门齿象属和间型豕棱齿象中，颊齿第二脊呈人字型, 釉质褶皱、齿谷中 小锥及白垩质发育强这些典型的豕棱齿象属(Choerolophodon)的特征较弱甚至缺失，但m3 齿脊数变多，这表明颌门齿象属可能起源于东亚的间型豕棱齿象。
分类： 生物学 >> 动物学 提交时间： 2017-11-07 合作期刊: 《古脊椎动物学报》
摘要： Dianmeisaurus gracilis is restudied on the basis of a new specimen. It provides some new information, especially that on the skull roof, to the species. The most striking of those new characters include the snout (preorbital region) shorter than the orbit, the interorbital septum extremely narrow, the frontal with a sharp process at both ends, and the posterior margin of the skull roof deeply V-shaped. A phylogenetic analysis with new information confirms that Dianmeisaurus is the sister group of Diandongosaurus and that these two genera, together with those Chinese taxa (Majiashanosaurus, Dianopachysaurus, Keichousaurus, and Dawazisaurus), form a monophyletic clade which is more closely related to the Nothosauroidea than to a clade formed by the European pachypleurosaurs.
分类： 地球科学 >> 地质学 提交时间： 2017-08-24 合作期刊: 《古脊椎动物学报》
摘要： The present paper revalidated Asiatosuchus nanlingensis Young, 1964 and Eoalligator chunyii Young, 1964 in taxonomy based on a detailed comparative study on those relevant specimens. New information derived from this study revealed that A. nanlingensis and E. chunyii were truly distinguishable from each other and therefore, diagnosis was further revised for each of them. A. nanlingensis is large, with a moderately long or a very elongate snout, and characterised mainly by the combination of the following characters such as: the quadrate with a lateral condyle much larger than the medial one, the surangular pinched off before reaching the end of the retroarticular process, the dental margins (at least the posterior portion) of the jaws nearly straight, and the presence of a fossa/sulcus on the lateral surface of the surangular lateral to the mandibular fossa. E. chunyii is a median-sized, short-snouted animal and characterised mainly by the combination of the following characters such as: the condyles of the quadrate similar in size, the dental margins of the jaws strongly concavo-convex, the dentary symphyses very short, the splenial not entering the mandibular symphysis, and the presence of a fossa/sulcus on the lateral surface of the surangular lateral to the mandibular fossa. With new information derived from this study, the phylogenetic relationships of A. nanlingensis and E. chunyii were tested, which did not support the view that the two species formed a monophyletic clade and opposed that E. chunyii could be considered as the synonym of A. nanlingensis. 根据对有关标本的详细对比研究，重新评估了南岭亚洲鳄(Asiatosuchus nanlingensis Young, 1964)和存义始猛鳄(Eoalligator chunyii Young, 1964)的分类。获得的新信息表明这两种是可以彼此区分的，因此对它们各自的鉴定特征进行了进一步修订。南岭亚洲鳄是个大型种类，它很可能具有中等或很长的吻部(眶前段), 主要由以下一些特征组合界定：方骨外髁比内髁大很多，上隅骨在反关节突近端尖灭，上、下颌齿缘(至少后段)几近平直，以及在下颌关节窝外侧上隅骨表面具一凹或纵沟。存义始猛鳄是个中型种类，主要可以由下列特征组合界定：方骨内、外关节髁大小几近相当，上、下颌齿缘强烈凹凸不平，齿骨联合很短，夹板骨不进入下颌联合，以及在下颌关节窝外侧上隅骨表面具一凹或纵沟。根据新的信息对南岭亚洲鳄和存义始猛鳄原来的系统关系进行了检验，所得结果不支持南岭亚洲鳄和存义始猛鳄可以形成一单系分支及反对后者是前者的同物异名。虽然本文研究表明南岭亚洲鳄可以和其他种类区分，但是在系统关系上却不能和亚洲鳄典型种(葛氏亚洲鳄Asiatosuchus grangeri)归于同一支系，如此应该为其建立一属。然而，鉴于南岭亚洲鳄标本太不完整，在没有新的、更完整的标本发现之前，本文仍沿用其原名，如德国亚洲鳄(Asiatosuchus germanicus)一样，后者也不和亚洲鳄典型种归于同一支系。
分类： 地球科学 >> 地质学 提交时间： 2017-08-10 合作期刊: 《古脊椎动物学报》
摘要： Dianmeisaurus gracilis is restudied on the basis of a new specimen. It provides some new information, especially that on the skull roof, to the species. The most striking of those new characters include the snout (preorbital region) shorter than the orbit, the interorbital septum extremely narrow, the frontal with a sharp process at both ends, and the posterior margin of the skull roof deeply V-shaped. A phylogenetic analysis with new information confirms that Dianmeisaurus is the sister group of Diandongosaurus and that these two genera, together with those Chinese taxa (Majiashanosaurus, Dianopachysaurus, Keichousaurus, and Dawazisaurus), form a monophyletic clade which is more closely related to the Nothosauroidea than to a clade formed by the European pachypleurosaurs. 根据一件产自云南罗平中三叠世关岭组II段的新标本并结合产自相同地点和地层中的模式标本对纤细滇美龙(Dianmeisaurus gracilis Shang & Li, 2015)进行了详细研究。原模式标本暴露其腹面，而新标本暴露其背面，两者互相补充提供了更完整、精确的纤细滇美龙解剖学信息。新材料揭示该种具有非常短小的吻部，眶前区的长度不仅短于眶后区长度，甚至短于眼眶的长度；外鼻孔小且位置靠前，即鼻孔前区的长度短于鼻孔后缘与眼眶前缘之间的距离；由两额骨构成的眼眶间隔非常狭窄，宽度小于顶骨平台宽度的1/3;额骨前后两端均具渐尖的突起；顶骨后部不收缩，顶骨平台后缘呈深V型。补充了新信息和包含更多属种(如Dawazisaurus)后的系统发育学分析支持了之前滇美龙和滇东龙互为姊妹群的结论，同时它们和马家山龙、滇肿龙、贵州龙和大洼子龙一起构成了一个仅由中国的属种组成的单系类群。与欧洲肿肋龙类群(Dactylosaurus, Anarosaurus, Serpianosaurus和Neusticosaurus)相比，这一单系类群与幻龙类有更近的亲缘关系。
分类： 生物学 >> 动物学 提交时间： 2021-07-30 合作期刊: 《古脊椎动物学报》
摘要： 乳齿象类是长鼻类演化的重要阶段，该阶段奠定了长鼻类各冠群演化的基本格局。乳齿象类的研究有400多年的历史，分类和命名经过多次修订改动，乳齿象类的演化脉络完全体现在乳齿象命名历史之中。从词源学角度考证乳齿象类各类群的命名来源，整理了175条乳齿象类的中文译名(绝大多数为有效分类名), 包括12个属以上分类群，46个属，117个种，涵盖了乳齿象类几乎全部的种属。在此基础上梳理了乳齿象类的演化脉络，提出乳齿象类分类和命名中存在的一些问题。乳齿象类的头骨和下颌的演化在各支系中都是连续的，体现出了相近的平行演化趋势，而颊齿的形态特征虽然区别不明显，但在各支系中相对稳定。豕棱齿象科(Choerolophodontidae)是乳齿象类中最稳健的单系群，其中厚棱象(Synconolophus)可能是有效属名；玛姆象科中，中新乳齿象(Miomastodon)和上新乳齿象(Pliomastodon)可能都是有效的，但不一定是美洲乳齿象(Mammut americanum)的直接祖先；铲齿象科(Amebelodontidae)中达氏铲齿象(Platybelodon danovi)与格氏铲齿象(P. grangeri)、赵氏隐门齿象(Aphanobelodon zhaoi)的系统发育关系存在疑问，取决于P.danovi的下门齿断面究竟是否为齿柱状结构，而美洲的布氏柱门齿象(Konobelodon britti) 可能是卢氏匙门齿象(Torynobelodon loomisi)的同物异名，亚洲归入Konobelodon的种不一定是铲齿象类，可能应归为副四棱齿象(Paratetralophodon); 嵌齿象科(Gomphotheriidae)中锯齿象属(Serridentinus)可能有效，它代表了嵌齿象类中一个偏轭型化的类群，向居维叶象亚科方向演化；居维叶象亚科(Cuvieroniinae)可能仅包括居维叶象(Cuvieronius)和喙嘴象(Rhynchotherium)属，而美洲其他的短颌嵌齿象类中，脊乳齿象(Stegomastodon)有可能从铲 齿象科中的一支演化而来，南方乳齿象(Notiomastodon)则可能与中华乳齿象(Sinomastodon)相关；Sinomastodon可能起源于中国南方的竹棚上新乳齿象(Pliomastodon (?) zhupengensis),原来的属型种中间中华乳齿象(Sinomastodon intermedius)具有早出原同名，建议以它的早出异名仙台中华乳齿象(Sinomastodon sendaicus)取代S. intermedius。
分类： 生物学 >> 动物学 提交时间： 2020-03-31 合作期刊: 《古脊椎动物学报》
摘要： The elephantimorph proboscideans, Serridentinus gobiensis Osborn & Granger, 1932, and Miomastodon tongxinensis Chen, 1978, from the Middle Miocene of northern China, were revised as Zygolophodon gobiensis (Osborn & Granger, 1932). However, their phylogenetic positions are still being debated because of their intermediate morphology between the typical bunodont (Gomphotheriidae) and zygodont (Mammutidae) elephantimorphs. In the present paper, we compare their dental and mandibular morphology with that of the Eurasian Z. turicensis, Gomphotherium subtapiroideum, and G. tassyi, as well as the North American Mio. merriami and G. productum. It appears that S. gobiensis and Mio. tongxinensis share with Mio. merriami the slightly more bunodont molar morphology than that of Z. turicensis, e.g., the thicker enamel, thicker pretrite crescentoids, higher interlophid enamel pillars in buccal view, and the narrower contour majorly caused by the narrower posttrite half loph(id)s. S. gobiensis and Mio. merriami also possess an “erected oval cross-sectioned mandibular tusk”, in which the cross-section is mediolaterally compressed (dorsoventral diameter being larger than the mediolateral one). Whereas, in Z. turicensis and G. productum, the mandibular tusk is “laid oval cross-sectioned”, in which the cross-section is dorsoventrally compressed (dorsoventral diameter is smaller than the mediolateral one). Therefore, it is reasonable to revive the genus Miomastodon Osborn, 1922, which contains the species that were previously attributed to Zygolophodon, but they have relatively bunodont molar morphology (i.e., the robust type of the Z. turicensis group). The mandibular tusk with erected oval cross-section seems to be a synapomorphy of Miomastodon species. Furthermore, the molar morphology of G. subtapiroideum and G. tassyi also exhibits intermediate status between the typical bunodonts and zygodonts. However, the mandibular symphysis of G. subtapiroideum and G. tassyi is stronger than that of Miomastodon, and the mandibular tusk is pyriform cross-sectioned. The validity of Miomastodon and G. subtapiroideum/tassyi obscures the boundary between the Gomphotheriidae and Mammutidae, and suggests that the evolutions of the Gomphotheriidae and Mammutidae are deeply involved in with each other, rather than straightforwardly detached. This phenomenon has been revealed by a collagen sequence analysis among Notiomastodon, Mammut, and extant elephants, which should be further studied.
分类： 物理学 >> 核物理学 提交时间： 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要： In the process of neutron spectrum measurement using the multi-sphere neutron spectrometer, energy response functions and detector readings should be applied to neutron spectrum unfolding. Mathematically, there can be multiple solutions to this problem, but only one actual neutron spectrum exists. Compared with common numerical spectrum unfolding methods, genetic algorithms have the characteristics of global optimization and probabilistic search. Therefore, they are chosen to be the spectrum unfolding algorithms for the multi-sphere neutron spectrometer (MNS IL100) developed by Tsinghua University. Firstly, the detector and different size polyethylene spheres of MNS IL100 were modeled to calculate the energy response functions by applying Monte Carlo simulation. Then based on the physical and mathematical properties of the spectrum unfolding problem by using genetic algorithms, effective search space and proper fitness function were determined to improve the efficiency of search and iteration. The elitism replacement scheme was used to ensure convergence and the pseudo-parallel strategy was used to inhibit premature convergence. According to the algorithms mentioned above, a spectrum unfolding code was developed and tested with several typical neutron spectra. At last, MNS IL100 and the spectrum unfolding code were used in actual experiment of 252Cf neutron source spectrum measurement. The experimental result is in good agreement with the 252Cf standard neutron spectrum, verifying the effectiveness and practicality of using genetic algorithms to unfold the neutron spectrum with combination of several processing strategies.
分类： 核科学技术 >> 核探测技术与核电子学 提交时间： 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
XI Jian-Bo
LIANG Hao
XIANG Shi-Tao
GUO Di
ZHOU Jin-Jin
LI Yu-Ying
LI Yang
LIU Han-Chao
ZHOU Yong-Zhao
LI Chun-Hua
ZHANG Jia-Wen
CHEN Jin
HE Kang-Lin
ZHU Ke-Jun
摘要： Resistive Plate Chambers (RPCs) built from a new type of Bakelite developed at Institute of High Energy Physics (IHEP), Chinese Academy of Sciences have been used in the BESIII Muon identification system for several years without linseed oil coating, but characteristic aging performances were observed. To adapt to the RPCs in the aging state, the front-end electronics have been upgraded by enhancing the front-end protection, improving the threshold setting circuit, and separating power supplies of the comparator and the field programmable gate array (FPGA). Improvements in system stability, front-end protection and threshold consistency have been achieved. In this paper, the system upgrade and the test results are described in detail.
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