A new family of primitive mammal from the Mesozoic of western Liaoning, China

A fairly well-preserved specimen of a new primitive mammal, Repenomamus robustus gen. et sp. nov., has been described from the Yixian Formation (Lower Cretaceous), western Liaoning, China. This animal has several derived characteristics, such as well-developed den-tary/squamosal articulation, reduced number of tooth, differentiation of premolars and molars in postcanine teeth, presence of a dorsal process of the premaxilla that is not in contact with the nasal, closed medial wall of the orbit, and presence of fingerlike promontorium on the petrosal. It also retains some primitive reptile-like features. It is the most primitive taxon among the three mammals known from the Jehol Biota, and also represents the largest mammal of Mesozoic age over the world.     

Mesozoic giant fleas from northeastern China (Siphonaptera): Taxonomy and implications for palaeodiversity

The recently discovered definite giant fleas from the Middle Jurassic Daohugou fauna and the Early Cretaceous Jehol fauna of northeastern China represent significant evidence for understanding ectoparasitism in the Mesozoic as well as the evolution of these giant blood feeders with their putative hosts (i.e. hairy or feathered vertebrates). On the basis of seven well-preserved specimens from Daohugou and Huangbanjigou we analyse the systematic classification of these primitive fleas, establishing two new genera and three new species as Pseudopulex wangi sp. nov., Hadropsylla sinica gen. et sp. nov., and Tyrannopsylla beipiaoensis gen. et sp. nov. All of them are assigned to the extinct siphonapteran family Pseudopulicidae, while the Early Cretaceous genus Tarwinia is transferred to Tarwiniidae fam. nov. The basal morphological disparities of Siphonaptera in the Mesozoic are evidenced by the occurrence of at least three distinct groups (pseudopulicids, tarwiniids, and saurophthirids). These disparate morphologies likely indicate adaptations to different hosts.     

Novel dental pattern in a Mesozoic mammal

Therian mammals have two families of postcanine teeth,premolars and molars, which primitively are morphologically distinct, but within each family, structure of the crowns changes in an evenly graded series from mesial to distal loci. Here we report a new Mesozoic basal therian in which the boundary between premolars and molars istransi tional but the molars form three abruptly discontinuous morphological grouos. containinh m1, m2-4.     

A Jurassic mammal from South America

The Jurassic period is an important stage in early mammalian evolution, as it saw the first diversification of this group, leading to the stem lineages of monotremes and modern therian mammals. However, the fossil record of Jurassic mammals is extremely poor, particularly in the southern continents. Jurassic mammals from Gondwanaland are so far only known from Tanzania and Madagascar, and from trackway evidence from Argentina. Here we report a Jurassic mammal represented by a dentary, which is the first, to our knowledge, from South America. The tiny fossil from the Middle to Late Jurassic of Patagonia is a representative of the recently termed Australosphenida, a group of mammals from Gondwanaland that evolved tribosphenic molars convergently to the Northern Hemisphere Tribosphenida, and probably gave rise to the monotremes. Together with other mammalian evidence from the Southern Hemisphere, the discovery of this new mammal indicates that the Australosphenida had diversified and were widespread in Gondwanaland well before the end of the Jurassic, and that mammalian faunas from the Southern Hemisphere already showed a marked distinction from their northern counterparts by the Middle to Late Jurassic.     

Pyrite framboids associated with the Mesozoic Jehol Biota in northeastern China: Implications for microenvironment during early fossilization

Despite of the recent influx of reports describing important fossil specimens from the Mesozoic Jehol Biota, detailed information on the mechanism of fossilization and paleoenvironment in which these fossils were deposited is scanty. We present an analysis of microenvironment based upon scanning electron microscope observations of in situ pyrite framboids and microcrystallines of plant and vertebrate feather fossils in the Jehol Biota. Pyrite microcrystallines and framboids occur extensively inside and on surface of plant fossils.Framboids found on feathers and in sedimentary matrix were in a lower abundance. These framboids have diameters ranging from 6 μm to 31 μm with an average of 20 μm, indicating a dysoxic aqueous condition with free oxygen level less than 30 μmol/L for the microenvironment where these framboids were formed. The outgrowth of framboids inside plant tissues suggests the presence of water molecules and free oxygen at the cellular level during pyritization; the relative timing between tissue decay and framboid formation implies a rapid tissue degradation occurred during the very early stage of fossilization. This line of reasoning is consistent with the observation that cell level structure of plant fossils from these deposits is rarely preserved. We propose a "fossil envelop" model to accommodate the different geochemical conditions between the microenvironment surrounding the fossil material and the macroenvironment of background lake bottom water.     

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.     

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, Lia- oning, is reported. The new species has a tooth formula I5- C1-P1-M3/i4-cl-pl-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 fea- tures. 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 mor- phology that is recognizable, except for that larger species are all from the Lujiatun bed of the Yixian Fro. A thorough and systematic analysis involving all the Jehol eu- triconodonts is needed to understand their phylogenetic relationships.     

关于华南推覆构造的商榷

根据前寒武纪花岗岩以及青白口纪火山岩与上(板)溪群之间的侵入接触关系,确定上溪群形成年龄为中元古代。皖南与赣东北蛇绿岩套的Sm-Nd定年结果为约1.0Ga。因此华南地块于中生代推覆到扬子地块上的模式不符合基本的地质事实。现有资料支持华夏和扬子两地块在晚元古代碰撞拼合的解释。     

A late Mesozoic high plateau in eastern China: Evidence from basalt vesicular paleoaltimetry

Eastern China is made of a number of large and small continental fragments throughout late Paleozoic and Mesozoic time,and is still the best natural laboratory for examining kinematic models of continent tectonics.The paleoelevation history of eastern China provides direct insight into the tectonic processes in China.Here we present basalt-vesicularity based estimates of the paleoaltimetry of the early Cretaceous basalts in northern East China,which indicate that the studied basalt units were at an elevation of more than 4 kilometers in late Mesozoic.Two vesicular basaltic rocks have been collected form bottom to top along the lava flow outcrop in eastern Inner Mongolia.After the digital precessing to the sample cross-sections,and taking advantage of the stereological conversion method to acquire the bubble size distributions,paleoelevation estimate was calculated for East China in the early Cretaceous.The results show that the elevation has been near 4700±750 m when the lava flows was cooling,implying that there were highland regions in the northern part of the East China Plateau during the early Cretaceous.Combined with other geological evidence,we conclude that there was a high plateau with elevation near 5000 m above sea level in Eastern China during the late Mesozoic.This ancient high plateau in eastern China was most likely formed by the collision of the north and south China blocks.     

Diverse transitional giant fleas from the Mesozoic era of China

Fleas are one of the major lineages of ectoparasitic insects and are now highly specialized for feeding on the blood of birds or mammals. This has isolated them among holometabolan insect orders, although they derive from the Antliophora (scorpionflies and true flies). Like most ectoparasitic lineages, their fossil record is meagre and confined to Cenozoic-era representatives of modern families, so that we lack evidence of the origins of fleas in the Mesozoic era. The origins of the first recognized Cretaceous stem-group flea, Tarwinia, remains highly controversial. Here we report fossils of the oldest definitive fleas--giant forms from the Middle Jurassic and Early Cretaceous periods of China. They exhibit many defining features of fleas but retain primitive traits such as non-jumping hindlegs. More importantly, all have stout and elongate sucking siphons for piercing the hides of their hosts, implying that these fleas may be rooted among the pollinating 'long siphonate' scorpionflies of the Mesozoic. Their special morphology suggests that their earliest hosts were hairy or feathered 'reptilians', and that they radiated to mammalian and bird hosts later in the Cenozoic.     

中国中生代反鸟类研究概述

对发现于中国中生代地层中的反鸟类化石进行了简单的总结.化石的系统分析表明,从晚侏罗世到早白垩世存在的反鸟亚纲的成员不仅数量多,而且存在较大的分异,与今鸟类存在较大的差异.它们繁盛于早白垩世,灭绝于晚白垩世.     

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.     

柞水县兽类调查报告

通过调查结果表明 ,柞水县境内共分布兽类 5 3种 ,隶属 6目、2 0科 .国家一级保护动物 2种 ,国家二级保护动物 8种 .从兽类区系成分看 ,柞水县古北界种类有14种 ,占全县兽类总数的 2 6.42 % ;东洋界种类 2 6种 ,占全县兽类总数的 49.0 6% ;广布种等 13种 ,占全县兽类总数的 2 4.5 3 % .     

中国东南部晚中生代伸展应力体制的岩石学标志

在中国东南部晚中生代时期（J2－K2），发育着大规模岩墙群、广泛的岩浆混合作用（包括侵入杂岩中的岩浆混合和火山岩中的复合岩流／双峰式火山岩）、大范围玄武岩浆的底侵、巨型链状火山岩带、晶洞花岗岩－A型花岗岩带、变质核杂岩，以及玄武岩的无斑隐晶－细粒结构和花岗岩的均匀块状结构。对它们的研究表明，它们形成于伸展应力体制，是伸展构造的岩石学标志，发生在晚中生代整个地质时期，并认为这一伸展构造由古太平洋库拉板块对欧亚板块的消减作用诱发。     

Geochemical characteristics and petrogenesis of Mesozoic basalts from the North China Craton： A case study in Fuxin, Liaoning Province

Occurrence of Cretaceous basalts in Fuxin County, Liaoning Province provides us an opportunity to understand Mesozoic mantle processes beneath the northern margin of the North China Craton (NNCC). Fuxin Jianguo basalts occur as volcanic channel phases with well-developed columnar jointings and contain few spinel lherzolite and pyroxenite xenoliths. They are poor in silica and rich in alkalis, Ti and Al, belonging to alkaline basalts. In trace element compositions, Jianguo basalts are moderately enriched in LREE and LILE, but not depleted in HFSE. They have low Sr and high Nd and Pb isotopic ratios. These geochemical characteristics suggest that Jianguo basalts originated from the depleted asthenosphere, representing an undifferentiated and uncontaminated primitive magma. Presence of these basalts indicates that the lithosphere beneath the region had thickness less than 65 km at the time of basalt eruption and was mainly composed of fertile pargasite-bearing spinel Iherzolite and plagioclase pyroxenite. The voluminous basaltic-andesitic magmatism during the early Jurassic-late Cretaceous time indicates that the commencement and accomplishment of lithosphere thinning in the NNCC was much earlier than that in the southern margin, since the mafic-intermediate volcanism only occurred at the Cretaceous time in the southern margin and the basalts with an asthenosphere isotopic signature at the Tertiary. This shows that highly spatial and temporal heterogeneity existed in the Mesozoic lithosphere evolution.     

辽西冀北晚中生代的化石蜥蜴类(爬行纲:有鳞目)

个蜥矢部部龙趾大具有辽西冀北晚中生代已记录的蜥蜴类化石共4属5种,及2个未命名属种。这些化石自下而上可划分4蜴类化石带：中侏罗世杨氏矢部龙带(Yabeinosaurus youngi Zone)、早白垩世早期长趾大凌河蜥-细小龙组合带(Dalinghosaurus longidigitus-Yabeinosaurus tenuis Assemblage Zone)、早白垩世早期细小矢带(Yabeinosaurus tenuis Zone)及早白垩世晚期炭德氏蜥带(Teilhardosaurus canbonarius Zone)凌河蜥-细小矢部龙组合带中的蜥蜴类属种最为丰富且分布较广,为研究早期蜥蜴类的地理地史分重要价值。布长等     

Late Pleistocene glaciation of the Changbai Mountains in northeastern China

The Changbai Mountains （2749 m a.s.l.） in northeastern China are one of the typical mountain regions with glaciation since late Pleistocene as evidenced by well-preserved erosive and accumulative landforms at elevations above 2000 m a.s.l, formed by glaciers around the crater lake, Tianchi Lake. Cirque glaciers developed on both the inner and outer sides of the volcanic cone. Well-preserved cirques, glacial trough valleys, glacial threholds, polished surfaces of the glacial erratics and the moraine ridges indicate that several glaciation processes took place during the last glacial period in this region. Resuits of optically stimulated luminescence （OSL） dating on the moraine sediments, and the K/Ar, thermal ionization mass spectrometry （TIMS）, electronic spinning resonance （ESR） dating on the volcanic rocks suggest two periods of glacier advances. One is named the Black Wind Mouth glacier advance taking place on the west and north slopes of the volcanic cone at an elevation of 2000-2100 m a.s.l., which is dated to about 20 ka, being the result of the Last Glacial Maximum （LGM）. The other is named the Meteorological Station glacier advance at the elevation of 2400-2600 m a.s.l., dated to 11 ka during the late glacial period, and is tentatively correlated to the Younger Dryas stage. The scope of the former glacier advance is larger than that of the latter. Regional comparisons showed that the glacial sequences in the Changbai Mountains are similar to other glaciated areas in eastern Asia during the later part of the last glacial cycle.