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首次调查了自贡恐龙化石及恐龙化石保护区内环境的放射性水平,结果发现,恐龙化石及其保护区内土壤、岩石的γ辐射剂量率,以及放射性核素^232Th、^40K的比活度,处于自贡市放射性本底值范围内,但恐龙化石中另两种放射性核素^238U、^226Ra的比活度,分别比同层岩石中的高26.6倍和29.2倍。 相似文献
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当前流行的陨星体撞击地球和大规模火山喷发两种假说,都不能从时间和空间上圆满地阐明,恐龙全球性地在白垩纪末期(距今6700万年前)同时灭绝的原因。在恐龙繁盛的侏罗纪(距今195~137百万年前)和自垩纪(距今137~67百万年前)早期的地层中,有许多恐龙骨骼化石保存,但未发现恐龙蛋化石,说明蛋已全部受精并孵出了恐龙。 相似文献
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1996年3月,中国科学院古脊椎动物与古人类研究所的专家们在河南省南阳市内乡县境内发掘出一具大型的较完整的恐龙骨骼化石,初步确定为原鸭嘴龙类,体长约4.5米,时代早于晚白垩纪。“内乡恐龙”骨骼化石和蛋化石的发现可追溯到三十年代。当地农民在耕作时发现骨化石和蛋化石并分别称之为“龙骨”和“石胆”。中药称其有“镇惊解挛,清热凉血”的功效。七十年代初,南阳地质调查四队在进行地质矿产普查中亦发掘了“石胆”、“龙骨”,经专家鉴定为恐龙骨骼和蛋化石。随后县文物工作者陆续在该县的赤眉镇,夏馆镇,马山口镇和七里坪乡4乡镇22个行政村均发现了恐龙骨骼及 相似文献
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现在,科技已能将灭绝的物种重新复活,那么,我们是否能像电影一样,让曾经的地球霸主——恐龙重现人世?复活灭绝动物,又将为生物链带来什么样的影响?1993年经典科幻电影《侏罗纪公园》描述这样一个故事:科学家们利用凝结在琥珀中的史前蚊子体内的恐龙血液提取出恐龙的遗传基因,加以修补和培育繁殖,将已经绝迹6500万年的史前庞然大物复活,使整个努布拉岛成为了恐龙的乐园。 相似文献
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长期以来,科学家普遍认为6500万年前的一颗小行星撞击地球造成了恐龙大灭绝,然而日前,美国俄勒冈州立大学古生物教授乔治·波尔纳却在新书《谁在咬恐龙?昆虫病菌和白垩纪之死》中提出了一个惊世骇俗的理论:虽然小行星撞地球给地球带来了巨大的生态灾难,然而,恐龙事实上却是被带有病菌的吸血昆虫给灭绝的,也就是说是昆虫引发的瘟疫造成了恐龙大灭绝。 相似文献
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位于我国西北部的陇中盆地古近纪—新近纪(第三纪)地层出露较好,并且产出大量哺乳动物化石和植物化石,这为西北地区地层对比和古气候研究提供了良好材料。近几十年,众多学者在陇中盆地的各次级盆地(如西宁盆地、兰州盆地、临夏盆地等)开展了大量古生物学、生物地层学、磁性地层学和古气候学研究,为探讨陇中盆地的构造演化过程和气候演变过程提供了重要参考。本文对陇中盆地第三纪地层年代学和古气候研究已取得的进展进行了初步总结归纳,并提出了需要进一步研究的问题。 相似文献
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The endemic South American mammals Meridiolestida, considered previously as dryolestoid cladotherians, are found to be non-cladotherian trechnotherians related to spalacotheriid symmetrodontans based on a parsimony analysis of 137 morphological characters among 44 taxa. Spalacotheriidae is the sister taxon to Meridiolestida, and the latter clade is derived from a primitive spalacolestine that migrated to South America from North America at the beginning of the Late Cretaceous. Meridiolestida survived until the early Paleocene (Peligrotherium) and early Miocene (Necrolestes) in South America, and their extinction is probably linked to the increasing competition with metatherian and eutherian tribosphenic mammals. The clade Meridiolestida plus Spalacotheriidae is the sister taxon to Cladotheria and forms a new clade Alethinotheria. Alethinotheria and its sister taxon Zhangheotheria, new clade (Zhangheotheriidae plus basal taxa), comprise Trechnotheria. Cladotheria is divided into Zatheria (plus stem taxa, including Amphitherium) and Dryolestida, including Dryolestidae and a paraphyletic array of basal dryolestidans (formerly classified as “Paurodontidae”). The South American Vincelestes and Groebertherium are basal dryolestidans. 相似文献
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The controversial family Adapisoriculidae, a group of shrew-sized Paleocene mammals, had proposed relationships with insectivores,
marsupials and more recently to plesiadapiforms. Adapisoriculid remains are numerous in the early Paleocene locality of Hainin,
Belgium, and allow us a test of these different phylogenetic hypotheses. Here, we identify the first tarsal bones of adapisoriculid
mammals. The highly specialised bones indicate an arboreal mode of life with euarchontan affinity. Moreover, the tarsal bones
are morphologically very close to those of the late Cretaceous Deccanolestes from the Deccan intertrappean beds of India, and also share several characters with the Paleocene plesiadapiforms and the
extant cynocephalid dermopterans. The adapisoriculid affinities of Deccanolestes are also confirmed by tooth morphology, indicating that Deccanolestes is a primitive member of this family. These phylogenetic affinities suggest a paleobiogeographic scenario for the family
with dispersal either via East Africa or across the Tethys area. 相似文献
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D. Angst C. Lécuyer R. Amiot E. Buffetaut F. Fourel F. Martineau S. Legendre A. Abourachid A. Herrel 《Die Naturwissenschaften》2014,101(4):313-322
The mode of life of the early Tertiary giant bird Gastornis has long been a matter of controversy. Although it has often been reconstructed as an apex predator feeding on small mammals, according to other interpretations, it was in fact a large herbivore. To determine the diet of this bird, we analyze here the carbon isotope composition of the bone apatite from Gastornis and contemporaneous herbivorous mammals. Based on 13C-enrichment measured between carbonate and diet of carnivorous and herbivorous modern birds, the carbonate δ13C values of Gastornis bone remains, recovered from four Paleocene and Eocene French localities, indicate that this bird fed on plants. This is confirmed by a morphofunctional study showing that the reconstructed jaw musculature of Gastornis was similar to that of living herbivorous birds and unlike that of carnivorous forms. The herbivorous Gastornis was the largest terrestrial tetrapod in the Paleocene biota of Europe, unlike the situation in North America and Asia, where Gastornis is first recorded in the early Eocene, and the largest Paleocene animals were herbivorous mammals. The structure of the Paleocene terrestrial ecosystems of Europe may have been similar to that of some large islands, notably Madagascar, prior to the arrival of humans. 相似文献
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Cerda IA Paulina Carabajal A Salgado L Coria RA Reguero MA Tambussi CP Moly JJ 《Die Naturwissenschaften》2012,99(1):83-87
Sauropoda is one of the most diverse and geographically widespread clades of herbivorous dinosaurs, and until now, their remains
have now been recovered from all continental landmasses except Antarctica. We report the first record of a sauropod dinosaur
from Antarctica, represented by an incomplete caudal vertebra from the Late Cretaceous of James Ross Island. The size and
morphology of the specimen allows its identification as a lithostrotian titanosaur. Our finding indicates that advanced titanosaurs
achieved a global distribution at least by the Late Cretaceous. 相似文献
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A new mammal, Mondegodon eutrigonus gen. et sp. nov., is described from the earliest Eocene locality of Silveirinha, Portugal. This species shows dental adaptations indicative of a carnivorous diet. M. eutrigonus is referred to the order Acreodi and considered, along with the early Paleocene North American species Oxyclaenus cuspidatus, as a morphological intermediate between two groups of ungulate-like mammals, namely, the triisodontids and mesonychians. Considering that triisodontids are early to early-late Paleocene North American taxa, Mondegodon probably belongs to a group that migrated from North America towards Europe during the first part of the Paleocene. Mondegodon could represent thus a relict genus, belonging to the ante-Eocene European mammalian fauna. The occurrence of such a taxon in Southern Europe may reflect a period of isolation of this continental area during the Paleocene/Eocene transition. In this context, the non-occurrence of closely allied forms of Mondegodon in the Eocene North European mammalian faunas is significant. This strengthens the hypothesis that the mammalian fauna from Southern Europe is characterized by a certain degree of endemism during the earliest Eocene. Mondegodon also presents some striking similarities with an unnamed genus from the early Eocene of India which could represent the first Asian known transitional form between the triisodontids and mesonychians. 相似文献
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Pascal Godefroit Lina Golovneva Sergei Shchepetov Géraldine Garcia Pavel Alekseev 《Die Naturwissenschaften》2009,96(4):495-501
A latest Cretaceous (68 to 65 million years ago) vertebrate microfossil assemblage discovered at Kakanaut in northeastern
Russia reveals that dinosaurs were still highly diversified in Arctic regions just before the Cretaceous–Tertiary mass extinction
event. Dinosaur eggshell fragments, belonging to hadrosaurids and non-avian theropods, indicate that at least several latest
Cretaceous dinosaur taxa could reproduce in polar region and were probably year-round residents of high latitudes. Palaeobotanical
data suggest that these polar dinosaurs lived in a temperate climate (mean annual temperature about 10°C), but the climate
was apparently too cold for amphibians and ectothermic reptiles. The high diversity of Late Maastrichtian dinosaurs in high
latitudes, where ectotherms are absent, strongly questions hypotheses according to which dinosaur extinction was a result
of temperature decline, caused or not by the Chicxulub impact. 相似文献
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Cabreira SF Schultz CL Bittencourt JS Soares MB Fortier DC Silva LR Langer MC 《Die Naturwissenschaften》2011,98(12):1035-1040
Post-Triassic theropod, sauropodomorph, and ornithischian dinosaurs are readily recognized based on the set of traits that
typically characterize each of these groups. On the contrary, most of the early members of those lineages lack such specializations,
but share a range of generalized traits also seen in more basal dinosauromorphs. Here, we report on a new Late Triassic dinosaur
from the Santa Maria Formation of Rio Grande do Sul, southern Brazil. The specimen comprises the disarticulated partial skeleton
of a single individual, including most of the skull bones. Based on four phylogenetic analyses, the new dinosaur fits consistently
on the sauropodomorph stem, but lacks several typical features of sauropodomorphs, showing dinosaur plesiomorphies together
with some neotheropod traits. This is not an exception among basal dinosaurs, the early radiation of which is characterized
by a mosaic pattern of character acquisition, resulting in the uncertain phylogenetic placement of various early members of
the group. 相似文献
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We describe the first known embryo of a neoceratopsian dinosaur, perhaps the most ubiquitous Laurasian group of Cretaceous dinosaurs, which is preserved completely enclosed within an egg. This specimen was collected from Late Cretaceous beds of southern Mongolia, which commonly preserve fossils of the neoceratopsian, Yamaceratops dorngobiensis. The small egg was scanned using high-resolution X-ray computed tomography and digitally prepared from the matrix. The preserved and imaged elements support a diagnosis of the embryo to Neoceratopsia and allow preliminary observations of ontogenetic transformations within this group. The addition of an embryo also adds another important data point to the already impressive postnatal ontogenetic series that are available for this clade. 相似文献
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The Paleocene–Eocene transition is of crucial interest for interpreting the Cenozoic evolutionary radiation of vertebrates. A substantial increase of the number of vertebrate families occurred between the Late Paleocene and Early Eocene, with the appearance of most of the representatives of extant lineages. Basal Eocene marine fish diversity is currently poorly known, exclusively restricted to two assemblages from Denmark and Turkmenistan, respectively. Exceptionally well-preserved articulated skeletal remains of fishes have recently been discovered from a basal Eocene sapropelitic layer exposed along the Kheu River in the Republic of Kabardino-Balkaria, northern Caucasus, Russia. Here, we report on Gerpegezhus paviai gen. et sp. nov., a new peculiar syngnathoid fish from this new Ciscaucasian locality. The morphological structure of the single available specimen suggests that it is the first long-bodied member of the superfamily Centriscoidea, representing the sole member of the new family Gerpegezhidae, which forms a sister pair with the extant family Centriscidae. 相似文献
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Epidemiologic study of tumors in dinosaurs 总被引:1,自引:0,他引:1
Occasional reports in isolated fragments of dinosaur bones have suggested that tumors might represent a population phenomenon. Previous study of humans has demonstrated that vertebral radiology is a powerful diagnostic tool for population screening. The epidemiology of tumors in dinosaurs was here investigated by fluoroscopically screening dinosaur vertebrae for evidence of tumors. Computerized tomography (CT) and cross-sections were obtained where appropriate. Among more than 10,000 specimens x-rayed, tumors were only found in Cretaceous hadrosaurs (duck-billed dinosaurs). These included hemangiomas and metastatic cancer (previously identified in dinosaurs), desmoplastic fibroma, and osteoblastoma. The epidemiology of tumors in dinosaurs seems to reflect a familial pattern. A genetic propensity or environmental mutagens are suspected. 相似文献