辽西热河生物群中的恐龙化石

我国的恐龙化石非常丰富，属种之多，延续时代之长，举世罕见，堪称“恐龙王国”。最近几年，我国辽西地区下白垩统热河群产出的恐龙化石再次引起了世界瞩目。从分类上讲，热河生物群中发现的第一块恐龙化石，是产出于朝阳县梅勒营子的鹦鹉嘴龙化石。鹦鹉嘴龙是一种亚洲特有的恐龙，因其吻部长得像鹦鹉嘴而得名。这种恐龙是一类两足行走的植食性动物，是许多恐龙研究学者感兴趣的一类恐龙。不过，真正把世界的目光引向辽西的发现，是带羽毛的兽脚类恐龙化石。中华龙鸟发现于辽西北票，从形态上看，它处在向鸟类演化的一个相对原始的进化水平…     

CT尺度下冻融岩石细观损伤特性分析

为研究冻融环境下岩石细观损伤演化规律,以红砂岩为研究对象,首先进行冻融循环试验,再对经历0次,5次,10次,20次和40次冻融循环的试样进行CT扫描.采用K均值聚类算法实现了扫描图像的二维孔隙识别;通过三维重构再现了红砂岩的冻融破坏模式,确定了试样的有效承载区,在细观层面实现了对岩石冻融损伤的定量分析.结果表明:通过K均值聚类算法确定阈值,可以有效实现CT图像的二值化;三维重构后的模型可以再现红砂岩试样在冻融过程中的损伤模式以及内部孔隙的发育特征;随冻融循环次数的增加,基于有效承载区定义的损伤变量逐渐增大,并与孔隙的发育趋势一致,能有效地反映冻融循环作用下岩石的损伤演化规律,为冻融岩石细观损伤研究提供了一种切实可行的方法.     

煤样力学特性与内部裂隙演化关系CT实验研究

为了观测煤样内部结构变化和裂隙演化过程,应用X射线工业CT对煤样在单轴加载不同阶段进行了扫描,获取了不同应力状态下CT图像。通过CT图像及其差值图像的统计特征值,分析了煤岩内部裂隙演化与宏观变形间的关系。分析表明:煤样CT图像灰度统计特征值的变化反映试件内部的密度变化,间接反映了试样中裂隙的发育发展过程;将CT图像中每个体素作为研究对象,CT的差值图像表征了试件内部裂隙缺陷体积的演化;CT差值图像的均值与方差更能体现宏观变形不同阶段内部裂隙的相应变化。     

基于岩石铸体薄片图像的数字岩心三维重构

由于岩心三维重构的CT扫描方法成本高昂,提出一个基于光学显微镜下铸体薄片图像的数字岩心三维重构方法。研究对采集的铸体薄片图像进行图像处理获得重构的训练图像模板,再应用多点地质统计学进行图像模板特征提取与数字岩心三维重构。实验采用鄂尔多斯盆地苏里格地区的若干岩心样本进行效果测试,结果表现为三维重构后的数字岩心孔径尺寸分布与真实值趋势相同,孔隙度的相对误差均在8%以内。上述研究内容表明基于岩石铸体薄片图像进行数字岩心的三维重构是有效的。     

基于砂岩三维数字岩心图像的图像处理与相划分研究

CT成像设备的发展和普及在石油工程、地球科学、地质学等领域和学科内发挥着越来越重要的作用。CT扫描成像可以在样本无损的条件下岩心等进行扫描重构获得的三维数字岩心图像,可以较为清楚的反映岩心内部结构;同时,基于CT扫描的岩心三维图像的分析,为油藏驱替原理分析和油田生产等方面有着重要的意义和作用。主要基于某砂岩岩心CT扫描后的重构灰度图,开发了一套应用于石油工程领域砂岩三维数字岩心图像的处理方法。首先,对图像处理过程中所应用的滤波和蒙版处理方法进行了简单的介绍;其次,详细介绍各图像滤波和蒙版处理方法的原理与其在三维数字岩心图像上的应用;最后在处理优化的图像之上,运用区域限定和活动收敛轮廓的方法,从而获得适用于油藏工程数值模拟分析的分相图像,将原始的数字岩心灰度图像划分成为了含孔隙、颗粒骨架和泥质三相的相划分图像。     

基于数字图像处理技术的沥青混合料级配检测方法

沥青混合料中级配对路用性能有着很大的影响,应用数字图像处理技术,对沥青混合料级配检测方法进行了改进研究。运用CT扫描技术扫描沥青混合料马歇尔试件的内部结构,获取数字图像,对获取的图像进行去噪、增强和分割等处理,在此基础上对图像进行伪三维级配识别。识别结果表明,对于直径大于2.36 mm以上的集料,通过误差修正可以使检测出的级配曲线和设计级配曲线更加接近,有效提高其识别精度。应用CT技术获取沥青混合料图像的方法,可以对其内部细观结构进行观测,并且避免了对试件造成破坏,从而可以对其宏观性能进行研究。     

埃德蒙顿龙的百年“寻亲”路

正埃德蒙顿龙的研究始于1917年,堪称最重要的鸭嘴龙科恐龙。目前这个属的化石记录仅限于北美洲坎潘阶与马斯特里赫特阶地层中。那么,为什么它们只存在于北美洲大陆?它们是如何演化的?它们的祖先是谁?与它同宗的"兄弟姐妹"又有哪些?平头鸭嘴龙类中的大块头儿鸭嘴龙类是一类演化非常成功的植食性恐龙,广泛存在于北美洲和亚洲的陆地生态系统,在欧洲及南美洲也有少量化石发现。根据头骨的形态特征,人们将鸭嘴龙类分为两大类:头顶平     

中国鳍龙类(爬行纲:双孔亚纲)研究进展

鳍龙类是中生代海洋中的顶级捕食者类群之一。中国关于鳍龙类的研究始于20世纪50年代末,先后在2个阶段内取得重要研究进展。近年来,中国华南地区三叠纪地层中发现了大量鳍龙类的新材料,对以往学界关于鳍龙类的起源、分布以及谱系演化研究构成了一定的挑战,并提出了很多新的科学问题。文章基于对中国的鳍龙类化石和地层信息的概览并与世界其他地方对比,认为鳍龙类可能起源于东特提斯区,且肿肋龙的单系性及其谱系发育位置有待进一步研究。此外,定量古生物学、CT和骨组织学等新方法、新技术的运用也将对中国鳍龙类的研究起到重要的推动作用。     

基于CT扫描的煤岩裂隙特征分析

本文通过实验研究,对煤样进行CT扫描,研究了煤岩裂隙的发育情况。同时应用Matlab对实验得到的CT图像进行处理,其中包括Canny算子边缘检测、图像二值化处理,使图像特征更加明显。利用盒维数法,定量化的描述煤岩裂隙的发育情况。通过对煤裂隙系统的分形特征在二维空间进行精确描述,得出1号煤样与2号煤样不同断面分形维数特征,找出了煤样图片数据中裂隙发育最为复杂的断面。     

基于数字图像处理技术的沥青混合料级配检测方法研究

沥青混合料中级配对其路用性能有着很大的影响,本文基于数字图像处理技术,对沥青混合料级配检测方法进行了改进研究。运用CT扫描技术扫描沥青混合料马歇尔试件的内部结构,获取数字图像,对获取的图像进行去噪、增强和分割等处理,在此基础上对图像进行伪三维级配识别。识别结果表明,对于直径大于2.36mm以上的集料,通过进行误差修正可以使检测出的级配曲线和设计级配曲线更加接近,有效提高其识别精度。应用CT技术获取沥青混合料图像的方法,可以对其内部细观结构进行观测,并且避免了对试件造成破坏,从而可以对其宏观性能进行研究。     

Discovery of a pterodactylid pterosaur from the Yixian Formation of western Liaoning, China

A well-preserved pterosaur with nearly complete skull is described from the Lower Cretaceous Yixian Formation at Sihetun in western Liaoning. It is characterized by a low and long crestless skull, slender and pointed teeth, long metacarpal, nearly equal length of metatarsals I–III and short pedal digit V. It is referred to a new genus and species of the family Pterodactylidae:Haopterus gracilis gen. et sp. nov. This is the first pterosaur with a nearly complete skull from the Jehol Biota; it also represents the first non-controversial fossil record of Pterodactylidae in Asia.Haopterus is more derived thanPterodactylus from the Late Jurassic Solnhofen in Germany. This discovery extends the distribution of the family Pterodactylidae from Europe and Africa to Asia and its latest occurrence from the Late Jurassic to the Early Cretaceous. The discovery ofHaopterus gracilis provides further evidence for the study of the origin and radiation of the Jehol Biota; it also sheds new light on the evolution and distribution of pterosaurs in the late Mesozoic.     

A pug-nosed crocodyliform from the Late Cretaceous of Madagascar

Although the image of crocodyliforms as 'unchanged living fossils' is naive, several morphological features of the group are thought to have varied only within narrow limits during the course of evolution. These include an elongate snout with an array of conical teeth, a dorsoventrally flattened skull and a posteriorly positioned jaw articulation, which provides a powerful bite force. Here we report an exquisitely preserved specimen of a new taxon from the Late Cretaceous of Madagascar that deviates profoundly from this Bauplan, possessing an extremely blunt snout, a tall, rounded skull, an anteriorly shifted jaw joint and clove-shaped, multicusped teeth reminiscent of those of some ornithischian dinosaurs. This last feature implies that the diet of the new taxon may have been predominantly if not exclusively herbivorous. A close relationship with notosuchid crocodyliforms, particularly Uruguaysuchus (Late Cretaceous, Uruguay) is suggested by several shared derived features; this supports a biogeographical hypothesis that Madagascar and South America were linked during the Late Cretaceous.     

Liaoxiornis delicatus gen. et sp. nov., the smallest Mesozoic bird

Recently, a very small and complete bird specimen was collected from theConfuciusornis-bearing Yixian. Formation. This finding represents a new kind of Mesozoic bird, namedLiaoxiornis delicatus. It is characterized by a short skull with teeth, a long neck and a very small sternum with only posterior process; the humeral head is not internally curved, and the hindlimbs are longer than the forelimbs.Liaoxiornis delicatus is not only much smaller thanConfuciusomis, but also smaller thanCathayomis and other early Cretaceous birds. It is the smallest bird known from Mesozoic deposit.Liaoxiornis provides new evidence indicating that the early adaptive radiation of birds is complicated.     

Sinobaatar gen. nov.: First multituberculate from the Jehol Biota of Liaoning, Northeast China

A multituberculate skeleton from the Lower Cretaceous Yixian Formation at Dawangzhangzi, Lingyuan City, Liaoning Province, Northeast China, provides new morphological information for early multituberculates. The specimen is the holotype of Sinobaatar lingyuanensis gen. et sp. nov. It has a narrow skull that lacks the superorbital crest or postorbital process. The dental formula is 3·?·5·2/1·0·3·2. The dental morphology, especially that of cheek teeth, of S. lingyuanensis is similar to that of Eobaatar, which places it in the family Eobaataridae. The postcranial skeleton of Sinobaataris similar to that of other multituberculates. As in Holotheria, Metatarsal V of Sinobaatar articulates only with the cuboid and has no contact with the calcaneus, which probably represents the primitive condition of multituberculates. Nine carpals of Sinobaatar resemble those of Zhangheotherium, except the centrale being larger than the trapezoid. The dental features of Sinobaatar show again that eobaatarids are obviously intermediate between Late Jurassic multituberculates and the later forms. Because eobaatarids are only known from the Early Cretaceous, the finding of Sinobaatar, therefore, supports that the age of the Jehol Biota is most likely Early Cretaceous.     

A transitional snake from the Late Cretaceous period of North America

Snakes are the most diverse group of lizards, but their origins and early evolution remain poorly understood owing to a lack of transitional forms. Several major issues remain outstanding, such as whether snakes originated in a marine or terrestrial environment and how their unique feeding mechanism evolved. The Cretaceous Coniophis precedens was among the first Mesozoic snakes discovered, but until now only an isolated vertebra has been described and it has therefore been overlooked in discussions of snake evolution. Here we report on previously undescribed material from this ancient snake, including the maxilla, dentary and additional vertebrae. Coniophis is not an anilioid as previously thought a revised phylogenetic analysis of Ophidia shows that it instead represents the most primitive known snake. Accordingly, its morphology and ecology are critical to understanding snake evolution. Coniophis occurs in a continental floodplain environment, consistent with a terrestrial rather than a marine origin; furthermore, its small size and reduced neural spines indicate fossorial habits, suggesting that snakes evolved from burrowing lizards. The skull is intermediate between that of lizards and snakes. Hooked teeth and an intramandibular joint indicate that Coniophis fed on relatively large, soft-bodied prey. However, the maxilla is firmly united with the skull, indicating an akinetic rostrum. Coniophis therefore represents a transitional snake, combining a snake-like body and a lizard-like head. Subsequent to the evolution of a serpentine body and carnivory, snakes evolved a highly specialized, kinetic skull, which was followed by a major adaptive radiation in the Early Cretaceous period. This pattern suggests that the kinetic skull was a key innovation that permitted the diversification of snakes.     

Baryonyx, a remarkable new theropod dinosaur

An extremely large claw bone, some 30 cm long, was found in Wealden (Lower Cretaceous) deposits in a Surrey claypit in January 1983. This led to the discovery the following month of the well-preserved skeleton of a new large theropod dinosaur. Only one other theropod specimen comprising more than a few bones had ever been found in Britain, and that discovery was more than a century ago. Indeed, no large theropod, reasonably complete, had previously been discovered in Lower Cretaceous rocks anywhere in the world. Our study so far suggests that the Surrey dinosaur was a typical large theropod in certain respects, resembling, for example Allosaurus. In several other respects, however, it differs sufficiently from all known dinosaurs to merit designation as the representative of a new species, genus and family.     

New fossil elaterid (Coleoptera: Polyphaga: Elateridae) from Yixian Formation of western Liaoning, China

A new species of the elaterid genus Cryptocoelus Dolin and Nel, 2002 from the Late Jurassic to Early Cretaceous Yixian Formation in the western Liaoning, China is described. Diagnosis of the genus is revised, and the systematic position of the genus is briefly discussed. Because the elaterids originated in the Early to Mid-Jurassic, this new material from the Late Jurassic-Early Cretaceous will enhance our understanding of the transition between ancient elaterids and extant ones, bridge the gap of cryptic relationships between the Mesozoic cupedids and elaterids, and expand our knowledge of their evolutionary history.     

贵州省盘县中三叠世羊圈幻龙新材料的研究

详细描述产自贵州省盘县新民乡羊圈村中三叠统关岭组上段的一件近于完整的羊圈幻龙新标本,并补充完善该种头后骨骼学信息。厘定后的羊圈幻龙的鉴定特征为:4个前颌骨獠齿后面跟着一个小的前颌骨齿;5~6个小的上颌骨齿后面跟着一对上颌骨獠齿;腕骨4块;间锁骨没有后突;荐椎4块;存在多指(趾)式。新标本的头后骨骼首次呈现一些原认为仅出现在幻龙属姊妹群——鸥龙属的一些特征,如间锁骨没有后突,腕骨4块,荐椎4块及存在多指(趾)式。这些特征的发现为深入认识和区分幻龙属和鸥龙属之间性状的异同提供了重要的信息。另外,新标本与羊圈幻龙模式标本,以及相同地点、相同地层层位产出的小吻幻龙模式标本IVPP V 14294在体型、齿式和头骨骨骼模式等高度一致,且与幻龙属其他种明显不同,因此认为它们系同物异名。鉴于N.rostellatus后出,应予弃用。     

New fossil elaterid (Coleoptera: Polyphaga: Elateridae) from Yixian Formation of western Liaoning, China

A new species of the elaterid genus Cryptocoelus Dolin and Nel, 2002 from the Late Jurassic to Early Cretaceous Yixian Formation in the western Liaoning, China is described. Diagnosis of the genus is revised, and the systematic position of the genus is briefly discussed. Because the elaterids originated in the Early to Mid-Jurassic, this new material from the Late Jurassic-Early Cretaceous will enhance our understanding of the transition between ancient elaterids and extant ones, bridge the gap of cryptic relationships between the Mesozoic cupedids and elaterids, and expand our knowledge of their evolutionary history.