Tribosphenic mammal from the North American Early Cretaceous

The main groups of living mammals, marsupials and eutherians, are presumed to have diverged in the Early Cretaceous, but their early history and biogeography are poorly understood. Dental remains have suggested that the eutherians may have originated in Asia, spreading to North America in the Late Cretaceous, where an endemic radiation of marsupials was already well underway. Here I describe a new tribosphenic mammal (a mammal with lower molar heels that are three-cusped and basined) from the Early Cretaceous of North America, based on an unusually complete specimen. The new taxon bears characteristics (molarized last premolar, reduction to three molars) otherwise known only for Eutheria among the tribosphenic mammals. Morphometric analysis and character comparisons show, however, that its molar structure is primitive (and thus phylogenetically uninformative), emphasizing the need for caution in interpretation of isolated teeth. The new mammal is approximately contemporaneous with the oldest known Eutheria from Asia. If it is a eutherian, as is indicated by the available evidence, then this group was far more widely distributed in the Early Cretaceous than previously appreciated. An early presence of Eutheria in North America offers a potential source for the continent's Late Cretaceous radiations, which have, in part, proven difficult to relate to contemporary taxa in Asia.     

A Chinese triconodont mammal and mosaic evolution of the mammalian skeleton

Here we describe a new triconodont mammal from the Late Jurassic/Early Cretaceous period of Liaoning, China. This new mammal is represented by the best-preserved skeleton known so far for triconodonts which form one of the earliest Mesozoic mammalian groups with high diversity. The postcranial skeleton of this new triconodont shows a mosaic of characters, including a primitive pelvic girdle and hindlimb but a very derived pectoral girdle that is closely comparable to those of derived therians. Given the basal position of this taxon in mammalian phylogeny, its derived pectoral girdle indicates that homoplasies (similarities resulting from independent evolution among unrelated lineages) are as common in the postcranial skeleton as they are in the skull and dentition in the evolution of Mesozoic mammals. Limb structures of the new triconodont indicate that it was probably a ground-dwelling animal.     

我国兽类群落生态学研究进展

从群落的组成、结构、动态与演替、种间关系等方面总结了我国兽类群落生态学的研究进展 .并讨论了目前我国兽类群落生态学研究存在的一些问题 .     

A new eutriconodont mammal from the early Cretaceous Jehol Biota of Liaoning,China

A new genus and species of eutriconodont mammal, Chaoyangodens lii gen. et sp. nov., from the Dawangzhangzi bed of Yixian Formation, Lingyuan, Liaoning, is reported. The new species has a tooth formula I5-C1-P1-M3/i4-c1-p1-m4, unique among eutriconodonts in having only one premolar in lower and upper jaws, respectively, and a distinctive diastema between the canine and the premolar. Its simple incisors and reduced premolars show a mosaic combination of primitive and derived features. This new taxon adds to the diverse group of Jehol eutriconodonts. Among the known species from at least three horizons, there seems no evolutionary trend in morphology that is recognizable, except for that larger species are all from the Lujiatun bed of the Yixian Fm. A thorough and systematic analysis involving all the Jehol eutriconodonts is needed to understand their phylogenetic relationships.     

草原沙蜥和避役骨骼解剖分析——游舌部蜥蜴(Ascalabotans)骨骼比较

以草原沙蜥和避役的骨骼解剖为素材,证明它们是较原始的蜥蜴,两者共同的原始性为:颞窝宽大,顶骨呈板状,牙齿三尖,下颌板骨前端参加下颌联合,环椎的间椎体同神经弧松散结合,荐椎无分化,尾椎脉弧呈Y型,腕骨超过9枚。各自的原始性状:草原沙蜥为顶骨孔发达,上颞骨存在,腭部骨片未退缩,而且排列位置未变。避役为上颞弧由后眶鳞骨构成。归纳喙头蜥、(?)鳞蜥、草原沙蜥和避役的骨骼结构,为原始蜥蜴特征提供新的证据。同时分析了游舌部蜥蜴的系统发育关系。     

A Cretaceous symmetrodont therian with some monotreme-like postcranial features

A new spalacotheriid mammal preserved with a complete postcranium and a partial skull has been discovered from the Yixian Formation of Liaoning, China. Spalacotheroid symmetrodonts are relatives to modern therians (combined group of marsupials and placentals) and are characterized by many skeletal apomorphies of therians. But unlike the closely related spalacotheroids and living therians, this new mammal revealed some surprisingly convergent features to monotremes in the lumbar vertebrae, pelvis and hindlimb. These peculiar features may have developed as functional convergence to locomotory features of monotremes, or the presence of lumbar ribs in this newly discovered mammal and their absence in its close relatives might be due to evolutionary developmental homoplasy. Analysis including this new taxon suggests that spalacotheroids evolved earlier in Eurasia and then dispersed to North America, in concordance with prevailing geodispersal patterns of several common mammalian groups during the Early Cretaceous period.     

Exploring the developmental potential of adult mammalian somatic cells

In the traditional ciews on developmental biology,the process of a mammal from a zygote to an adult individual follows continuous changes of space and time environments and is the result of different expressions of target genes.It has long been known that this process is irreversible and the terminal differentiated adult cells,such as cardiac myocytes andneurons,will not divide and differentiate.But recent reports on the two hottest fields—cloning medicine and stem cell biology doubted these concepts.This may lead to a further understanding of the potentiality of mammal development and may provide great chances for commercial andd clinical practice.     

Mammal teeth from the Cretaceous of Africa

We report here the discovery of two mammal teeth from the early Cretaceous of Cameroon. These, and some jaw fragments, all from Cameroon, are the only fossil evidence of mammalian evolution from Africa between late Jurassic and Paleocene, a span of at least 85 million years. A triangular upper tooth lacks the principal internal cusp of marsupials and placentals and is therefore of a similar evolutionary grade to most Jurassic and early Cretaceous therian mammals, but more primitive than the metatherian-eutherian grade. Early Cretaceous, or older, therian mammals are now known from all southern continents except Antarctica. The new find from Cameroon is consistent with the hypothesis that marsupials, the dominant living mammals of South America and Australia, were not present on any Gondwana continents until after the early Cretaceous separation of Africa by the opening of the South Atlantic.     

Convergent dental adaptations in pseudo-tribosphenic and tribosphenic mammals

Tribosphenic molars of basal marsupials and placentals are a major adaptation, with the protocone (pestle) of the upper molar crushing and grinding in the talonid basin (mortar) on the lower molar. The extinct pseudo-tribosphenic mammals have a reversed tribosphenic molar in which a pseudo-talonid is anterior to the trigonid, to receive the pseudo-protocone of the upper molar. The pseudo-protocone is analogous to the protocone, but the anteriorly placed pseudo-talonid is opposite to the posterior talonid basin of true tribosphenic mammals. Here we describe a mammal of the Middle Jurassic period with highly derived pseudo-tribosphenic molars but predominantly primitive mandibular and skeletal features, and place it in a basal position in mammal phylogeny. Its shoulder girdle and limbs show fossorial features similar to those of mammaliaforms and monotremes, but different compared with those of the earliest-known Laurasian tribosphenic (boreosphenid) mammals. The find reveals a much greater range of dental evolution in Mesozoic mammals than in their extant descendants, and strengthens the hypothesis of homoplasy of 'tribosphenic-like' molars among mammals.     

原始宗教对白裤瑶民俗竞技文化发展的影响

从原始宗教的视角对居住在南丹白裤瑶的民俗竞技文化进行研究。研究表明,白裤瑶有自然崇拜、图腾崇拜和祖先崇拜的原始宗教情结,原始宗教对白裤瑶民俗竞技文化的发展起到了积极的作用,正是由于原始宗教的存在而使白裤瑶民俗竞技文化源远流长,内容丰富,富有民族特色和生活气息。     

卧龙自然保护区的兽类研究

本文记录了卧龙自然保护区的兽类95种或亚种,隶属7目23科65属;分折了兽类区系组成、生态类群与空间的关系、地理分布及其特点,以及种群的相对数量,对进一步研究卧龙的兽类和自然保护管理有理论和实践意义。     

藏族先民的原始信仰--略谈藏族苯教文化的形成及发展

苯教是藏族本土宗教,有几千年的悠久历史。尽管佛教在青藏高原的传入给苯教带来了极大的冲击,它还是凭借极强的生命力一直延续至今。研究苯教文化对藏族古代政治、经济、社会以及民风民俗的研究有极高的参考价值。文章对藏族先民的原始信仰及特征、拥仲苯教的形成及教义等方面进行了探讨。认为,藏族原始苯教属自然宗教类“,万物有灵”及“以人为中心”思想是原始苯教的两大特点;拥仲苯教是由顿巴辛绕在藏族原始苯教的思想基础上,对其祭祀内容、祭祀方式、祭品等方面进行重大改革,并加以理论化的产物。     

本原半环的稠密性及Kaplansky定理

若半环S有忠实既约S－半模M，叫S为本原半环，证明了本原半环具有稠密性，然后在此基础上证明了名的Kaplansky定理，即PI－本原半环是单的，在其中民上是有限维的。     

哺乳动物植入前胚胎发育的程序化

哺乳动物植入前胚胎发育的程序化过程,是发育生物学的核心问题,弄清这一过程,对研究哺乳动物早期发育有着重要意义.因受研究方法、实验材料等因素的影响,该研究领域的进展缓慢.文章就近年来在植入前胚胎发育的分子事件、母源调控向合子型调控的过渡、细胞核重建、染色质的重建机制、基因组甲基化与基因表达等方面的研究进展进行了综述.     

论"梅葛"的历史文化特点

“梅葛”是楚雄彝族最具有代表性的原始性史诗,与民族同生共长,并与原始宗教祭祀、节日庆典、礼仪民俗融为一体,蕴含着丰富的历史文化特点,如充满浓厚、神秘的原始宗教观念,展示了楚雄彝族家庭婚姻和传统伦理道德的演变过程,同时还揭示了彝族社会生产力从低到高不断发展变化的历史进程,阐述了彝族从游牧到旱稻兼作或稻作的农耕演变规律。     

七种脊椎动物肝细胞核质比例研究

本文研究了从鱼类到哺乳类七种脊椎动物肝细胞,探索了不同动物肝细胞及同种动物不同发育时期肝细胞的大小、核的大小、细胞体积、核的体积、核质指数相应的变化。这种变化反映了细胞的形态和机能矛盾的统一是生物进化的原因之一。     

New primitive ichthyosaurian （Reptilia,Diapsida） from the Middle Triassic of Panxian,Guizhou, southwestern China and its position in the Triassic biotic recovery

A new primitive ichthyopterygian Xinminosaurus catactes gen. et. sp. nov. is erected based on a complete skeleton from the Middle Triassic Upper Member of the Guanling Formation at Panxian, Guizhou, southwestern China. It has a suite of uniquely derived char- acters in its dentition, ulna, carpals and tarsals. It is similar to primitive ichthyopterygians in retaining elongated limb bones. The new taxon and a diversity of marine reptiles in Panxian Fauna are the physical markers of the Middle Triassic Biotic radiation. Detailed studies of this fauna will supply essential knowledge on the diversity, migration and paleobiogeographic affinity of Middle Triassic ichthyopterygians.     

论古希腊神话所反映的希腊早期社会形态

希腊神话是希腊原始初民的艺术，反映了人类原始的审美理想，理想根植于现实，神话作为文学的一部分，也必然是现实生活的反映。希腊神话的产生与发展经历了人类童年时代发展的最完美的整个过程，反映了希腊社会由低级到高级，由母权制到父权制，由蒙昧时代的杂婚制到野蛮时代一夫一妻制的一系列变化，所谓希腊神话正是一部充满人间烟火气息的巨著。     

原生态演唱的当代意义及保护

分析了原生态唱法的价值、意义,认为原生态作为一种新的唱法,正在为大众所接受,它的当代意义不仅仅是它所带来的社会反映和商业价值,更重要的是它冲击了"传统"的音乐教育和音乐欣赏方法,在保护非物质文化遗产和弘扬民族文化艺术方面起了重要的推动作用。提出了保护原生态唱法的具体措施。     

闻一多论原始思维的象征性特征

原始思维有其独特的表达方式和心理基础，象征性是其中最重要特征之一。象征是“有意味的形式”，其特点在于“借此而言彼”，具有朦胧性和多义性，神秘性与含蓄性。文章旨在探讨闻一多在古代典籍中所揭示的原始思维的象征性特征及意义。