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151.
黔东早—中寒武世凯里组疑源类组合及其界线意义   总被引:13,自引:0,他引:13  
通过对台江八郎和丹寨两条剖面凯里组中疑源类化石的分析,研究,台江剖面产疑源类化石有17属35各(12未定种),其中以Leiosphaeridia,Synsphareidium,Cymatiosphaera,Pterospermella最为丰富,可划分为3个组合,即Cymatiosphaera cf.cristata-Fimbriaglomerella memebrancea组合,Cristallinium-Micrhystridium-Pterospermella组合和Dictyotidium-Granomarginata组合,丹寨平寨剖面凯里组所产疑源类化石有:13属21种(5未定种),同样划分为3个组合,即Leiosphaeridia-Tasmanites组合,Retisphaeridium-Micrhystridium tentatium组合和Baltisphaeridium-Bubomorpha hunjiangensis组合,本文对两条剖面中的凝源类化石的组成,相对含量做了详细的统计,发现在八郎剖面9-2层和平寨剖面3层疑源类的丰度,分异度开始发生明显的变化,表现由早寒武世向中寒武世疑源类组合面貌的转变,这一疑源类转变层位正好是与三叶虫划分的中,下寒武统界线的层位位置相一致,这充分表明疑源类化石可作为划分中,下寒武统的极有价值的微体生物化石证据。  相似文献   
152.
记广西田东却林缅甸先炭兽的新材料   总被引:2,自引:0,他引:2  
李茜  陈耿娇 《古脊椎动物学报》2001,39(4):291-296,T001
记述了产自广西田东县却林那读组中一残破的缅甸先炭兽 (Anthracokeryxbirmanicus)头骨。通过对化石的描述 ,对该种特征进行了补充和分析 ,并认为其终生生长的上犬齿可能是用来作为争夺领域和配偶的武器。终生生长的上犬齿的发现 ,证明炭兽类具有性双形。将那读动物群和缅甸邦唐动物群进行对比 ,认为那读组的时代很可能有一部分属于中始新世  相似文献   
153.
The fossil record of metriorhynchids and plesiosaurians from the Rosso Ammonitico Veronese Formation (RAVFm, Middle–Upper Jurassic, Italy) is represented by elements collected between the eighteenth and twentieth centuries. All the metriorhynchid material is referred to the genus Neptunidraco. The first RAVFm plesiosaurian material was collected in the nineteenth century and referred to Plesiosaurus: elements are here described and interpreted as a chimerical association of crocodylomorph and plesiosaurian bones, providing the first co-occurrence of these clades in the RAVFm. The second plesiosaurian is the associated skeleton that we refer to Anguanax zignoi gen. et sp. nov. Bayesian phylogenetic analysis confirms the basal geosaurine affinities of Neptunidraco resulted by parsimony analysis. Using both methods, Anguanax was recovered as a basal pliosaurid, sister group of the clade including Marmornectes and Thalassophonea. Bayesian inference methods indicate that both Italian lineages diverged from other known lineages between 176 and 171 Mya, also showing divergence rates significantly higher than any other representative of their respective clades. We suggest a phase of rapid evolutionary adaptation to deeper marine environments in the ancestors of the Rosso Ammonitico Veronese reptiles as a response to the latest Liassic regressive regime in Northern Tethys.  相似文献   
154.
 Fossil vegetative and reproductive structures from deposits of the Raritan Formation in New Jersey (Turonian, Upper Cretaceous, ∼90 MYBP) include ferns, gymnosperms, and angiosperms. Gymnosperms collected from this formation have been known since the beginning of the 20th century. Fossil leaves, wood and seed cones have been are identified as belonging to the Cupressaceae, Pinaceae, and Taxodiaceae. In the present contribution, we describe a series of fossil dwarf shoots, leaves and a pollen cone belonging to the family Pinaceae. Fossils are charcoalified with preserved three-dimensional structure and excellent cellular detail. The dwarf shoots are assigned to a new species Prepinus crossmanensis sp. nov. and to the previously described Pinus quinquefolia Jeffrey. The new species Prepinus crossmanensis differs in size, shape, presence of hypodermis, sclerenchyma and stomata in the cataphylls, and number and shape of needle leaves from previously known species. Also, isolated leaves were found that were assigned to the new species, Prepinus raritanensis sp. nov. The new species is differentiated by the size and shape of stomata, the presence of number of layers of the hypodermis; and the cell-shape and number of layers of the mesophyll and transfusion tissue. A previously undescribed male cone, Amboystrobus cretacicum gen. and sp. nov., has an axis with spirally attached microsporophylls, each bearing two abaxial ovoid microsporangia. The pollen grains are monosulcate and bisaccate (eusaccate), with an elliptical corpus, granulate exine sculpture, and honeycomb-like wall structure. Received March 21, 2000 Accepted November 13, 2000  相似文献   
155.
Didactyl tracks of theropod affinity are reported in this study based on a small sample of footprints in sandstones within the Middle Jurassic (Aalenian-Bajocian) Dansirit Formation in the Baladeh area, Alborz Mountains, Iran. These tracks superficially resemble footprints attributed to small deinonychosaurian dinosaurs known mainly from the Cretaceous of Asia. The relative length of the traces of digits III and IV is atypical for deinonychosaurids, especially dromaeosaurids, but could potentially be attributed to a troodontid-like trackmaker. The possibility of small Middle Jurassic deinonychosaurian trackmakers cannot be ruled out on the basis of the age of these traces. However, reports of pre-Cretaceous tracks of deinonychosaurian or deinoychosaur-like affinity remain rare and problematic. To date previous reports of pre-Cretaceous didactyl tracks pertain to a variable range of footprint morphologies, some of which predate known deinonychosaurian body fossil occurrences.  相似文献   
156.
157.
A new species, Buxus pliosinica H.S. Huang, T. Su et Z.K. Zhou n. sp. (Buxaceae) is designated based on leaf architecture and cuticular features of five compressed fossil leaves from the Upper Pliocene Sanying Formation of Yunnan, SW China. Leaves of B. pliosinica are elliptic and small, with entire margin, retuse tip, intramarginal vein, and exmedially ramified tertiary veins. The leaves are hypostomatic with anomocytic stomatal apparatuses and giant stomata. Based on comparisons of leaf morphological and cuticular features, B. sempervirens Linnaeus is considered as the nearest living relative of B. pliosinica. Morphologically, these species share similar elliptic shape and size, cuneate base, retuse tip, similar ranges of petiole length, angles of 2° vein to midvein, and distance from the intramarginal vein to the margin. In terms of cuticular features, they are similar in type of stomatal apparatus, maximum length of giant stomata and range of stomatal length, but differ in the presence of indumentum. This discovery represents the first fossil record of Buxus from the SE margin of the Tibetan Plateau, and confirms the existence of Buxus in this region by the late Pliocene. Meanwhile, the newly described fossil species contributes to our understanding of the evolution of extant Buxus.  相似文献   
158.
Two new dinosaur tracksites are reported from the Lower Cretaceous Jiaguan Formation in the Sichuan Basin, Qijiang District of Chongqing. These are the Gaoqing-Yongsheng and the Huibu tracksites, which represent the 13th and 14th reports from this formation. The Gaoqing-Yongsheng tracksite reveals the trackway of a large biped (ornithopod) in association with isolated sauropod tracks and large indeterminate undertracks with radial cracks. These features are preserved as natural casts with pebble infillings in a coarse, cross bedded and very thick bedded sandstone sequence. The Huibu tracksite reveals isolated theropod tracks and ornithopod tracks, the latter having a quadripartite, Caririchnium-like morphology, preserved in a thin bedded sandstone sequence with intercalated mudstone.  相似文献   
159.
贵州凤冈早志留世孢子组合的发现及其古植物学意义   总被引:3,自引:2,他引:1  
王怿  欧阳舒 《古生物学报》1997,36(2):217-237
系统描述贵州凤冈早志留世的孢子5属12种,其中包括1新种。根据其组合特征,确认其时代为Llandoverian晚期,通过对三缝孢的性状分析,认为在早志留世Llandoverian晚期已确有维管植物的存在。  相似文献   
160.
河南内乡晚奥陶世石燕河组牙形石及其地质意义   总被引:3,自引:0,他引:3  
梅仕龙 《古生物学报》1995,34(6):674-687
将河南内乡晚奥陶世石燕河组牙形石自下而上建立了Oulodusuirichi-Aphelognathusshoshonensis带,Onodusrobustus带,Aphelognathusgrandis带,Aphelognathusdivergens带和Aphelognathuszuoquensis带。这个序列与北美中大陆的很相似,两者可详细对比。充分证实了北美中大陆型牙形石动物群以及中国合此类型牙形石的最高奥陶纪地层在华北地台以南的武当地块北缘的存在,并指明了其古生物地理分区和构造意义。  相似文献   
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