首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 46 毫秒
1.
Some of the best records of continental vertebrates from the Cretaceous of Europe come from Romania, particularly two well-known occurrences of dwarfed and morphologically aberrant dinosaurs and other taxa that lived on islands (the Cornet and Haţeg Island faunas). Substantially less is known about those vertebrates living in the more stable, cratonic regions of Romania (and Eastern Europe as a whole), particularly during the earliest Cretaceous. We describe one of the few early Early Cretaceous fossils that have ever been found from these regions, the tooth of a large theropod dinosaur from Southern Dobrogea, which was discovered over a century ago but whose age and identification have been controversial. We identify the specimen as coming from the Valanginian stage of the Early Cretaceous, an incredibly poorly sampled interval in global dinosaur evolution, and as belonging to Carcharodontosauridae, a clade of derived, large-bodied apex predators whose earliest Cretaceous history is poorly known. Quantitative analyses demonstrate that the Romanian tooth shows affinities with a derived carcharodontosaurid subgroup, the Carcharodontosaurinae, which until now has been known solely from Gondwana. Our results suggest that this subgroup of colossal predators did not evolve vicariantly as Laurasia split from Gondwana, but originated earlier, perhaps in Europe. The carcharodontosaurine diversification may have been tied to a north-to-south trans-Tethyan dispersal that took place sometime between the Valanginian and the Aptian, illustrating the importance of palaeogeographic ties between these two realms during the largely mysterious early–mid Early Cretaceous.  相似文献   

2.
Here we describe an isolated tooth of a metriorhynchid crocodylomorph from the Hybla Formation (Aptian, Lower Cretaceous) of Rocca Chi Parra quarry (Montagna Grande, Calatafimi, Trapani Province), Sicily, Italy. The specimen shares with the Upper Jurassic taxon Plesiosuchus manselii a mediolaterally compressed conical tooth crown, noticeable lingual curvature, mesial and distal carinae with microscopic, rectangular contiguous denticles, strong distal curvature of the mesial margin, and the presence of weak 'carinal flanges' on the labial and lingual surfaces (which are preeminent at the mid-crown). This suite of morphologies is also present in an unnamed Valanginian (Lower Cretaceous) plesiosuchinan from France. However, the Sicilian tooth differs from these taxa in having more pronounced carinae, and faint apicobasally aligned enamel ridges. It also differs from P. manselii in having more extensive 'carinal flanges' on the labial surface. The specimen extends the known geological range of Metriorhynchidae and Thalattosuchia by approximately 7–8 million years. This overturns previous hypotheses of Metriorhynchidae becoming extinct early in the Early Cretaceous.  相似文献   

3.
Dinosaur skin impressions are rare in the Upper Jurassic Morrison Formation, but different sites on the Howe Ranch in Wyoming (USA), comprising specimens from diplodocid, camarasaurid, allosaurid and stegosaurian dinosaurs, have proven to be a treasure-trove for these soft-tissue remains. Here we describe stegosaurian skin impressions from North America for the first time, as well as the first case of preservation of an impression of the integument that covered the dorsal plates of stegosaurian dinosaurs in life. Both have been found closely associated with bones of a specimen of the stegosaurian Hesperosaurus mjosi Carpenter, Miles and Cloward 2001. The scales of the skin impression of H. mjosi are very similar in shape and arrangement to those of Gigantspinosaurus sichuanensis Ouyang 1992, the only other stegosaurian dinosaur from which skin impressions have been described. Both taxa show a ground pattern of small polygonal scales, which in some places is interrupted by larger oval tubercles surrounded by the small scales, resulting in rosette-like structures. The respective phylogenetic positions of G. sichuanensis as a basal stegosaurian and H. mjosi as a derived form suggest that most stegosaurians had very similar skin structures, which also match the most common textures known in dinosaurs. The integumentary impression from the dorsal plate brings new data to the long-lasting debate concerning the function of dorsal plates in stegosaurian dinosaurs. Unlike usual dinosaur skin impressions, the integument covering the dorsal plates does not show any scale-like texture. It is smooth with long and parallel, shallow grooves, a structure that is interpreted as representing a keratinous covering of the plates. The presence of such a keratinous covering has affects on all the existing theories concerning the function of stegosaurian plates, including defense, thermoregulation, and display, but does not permit to rule out any of them.  相似文献   

4.
The spotty nature of the terrestrial fossil record for the Mesozoic hinders a more complete understanding of dinosaur diversity. For stegosaurs (Ornithischia), the plated dinosaurs, only a few and fragmentary remains are reported from the Early Cretaceous of Europe. A recent revision concluded that only a partial vertebra of the nomen dubium Craterosaurus (?Aptian, England) could be considered as stegosaurian. Here we report on a stegosaur tooth from the Early Cretaceous (Berriasian) Purbeckian deposits of Cherves-de-Cognac (Charente), southwestern France. This tiny tooth was examined in detail using microtomography. Comparisons being limited by the rarity of stegosaur tooth rows material (e.g., from the skull of the holotype of Stegosaurus stenops) and dental material, notably from Europe, we observed new material of cf. Stegosaurus armatus and Hesperosaurus mjosi from the Upper Jurassic Morrison Formation of Wyoming (USA). The tooth shows the most similarities to the Late Jurassic genera Stegosaurus and Hesperosaurus, but differs in having a distinctive downwardly arched (V-shaped) cingulum on the ?lingual face (maxillary tooth hypothesis). It is referred to as Stegosauria indeterminate, a medium-sized quadrupedal herbivore that inhabited an emerged land between the Armorican Massif and the Massif Central. This finding is the first evidence of a stegosaur from the Early Cretaceous of France and a welcome addition to the meagre European record of that time. In addition, it is the second stegosaurian tooth crown reported from Europe. The assemblage of ornithischians of Cherves-de-Cognac shares some similarities with that of the Early Cretaceous (Berriasian) of the Purbeck Limestone Group, southern England. The relative rarity of ornithischian osteological remains in both Purbeckian environments suggests that most of these dinosaurs were mainly inhabitants of inland terrestrial palaeoenvironments.  相似文献   

5.
The stratigraphic division and sequence of the Upper Cretaceous sediments in eastern Heilongjiang Province,China,have been ambiguous and controversial,mainly due to a lack of biostratigraphically useful fossils and related radiometric dating.A new species of angiospermous fossil plant.Platanus heilongjiangensis sp.nov.,from Qitaihe in eastern Heilongjiang has been found in sediments conformably above which zircons from a rhyolitic tuff has been dated by U-Pb radiometric methods as 96.2± 1.7 Ma.indicating that the Upper Houshigou Formation is of Cenomanian age.This discovery not only provides new data to improve our stratigraphic understanding of the Houshigou Formation,but also shows that Platanus flourished in the early Late Cretaceous floras of the region.This new study also indicates active volcanism taking place in the eastern Heilongjiang region during the Cenomanian of the Late Cretaceous.  相似文献   

6.
Pedogenic carbonates were collected from Early Cretaceous strata in Sichuan and Liaoning, China. These paleosol carbonates and calcareous paleosols were evaluated in order to reconstruct atmospheric CO2 concentrations during the Early Cretaceous using a paleosol barometer. Using the isotopic ratios of pedogenic carbonates from Early Cretaceous (early-middle Berriasian, early Valanginian) strata in Sichuan Basin, averaged atmospheric pCO2 is estimated to have been 360 ppmv in the early-middle Berriasian and a mean value of 241 ppmv in the early Valanginian. In the late Barremian in western Liaoning, however the average was 530 ppmv, with a range of 365 ppmv and 644 ppmv, lower than previous estimates of pCO2 for these time periods, consistent with the suggestion of overall climate cooling and paleotemperature fluctuation during the Early Cretaceous. This indicates that not all of the Cretaceous was a high or continuous CO2 greenhouse, especially during Early Cretaceous.  相似文献   

7.
The Yixian Formation (Lower Cretaceous) of China is famous for its fossils of early angiosperms, and these fossils have shed otherwise unavailable light on the evolution of angiosperms. The seeds in Archaefructus and Nothodichocarpum are inserted along the dorsal of the fruits while those in Sinocarpus are along the ventral of the fruits, suggesting different Bau‐plans and pathways deriving the carpels in these plants of the Early Cretaceous. Adding further fossil evidence, here we report a novel fossil angiosperm, Neofructus lingyuanensis gen. et sp. nov, with its seeds inserted on both ventral and dorsal sides of the fruits documented through light microscopic and SEM observations, suggesting a novel way forming gynoecium in the Yixian Formation. These fossil angiosperms indicate that angiosperm gynoecia in the Yixian Formation (the Barremian to Aptian) are derived in obviously different ways, implying an evolutionary scenario for angiosperms quite different from formerly assumed.  相似文献   

8.
黑龙江省东部中侏罗世至早白垩世沟鞭藻组合序列   总被引：5，自引：0，他引：5  
祝幼华  何承全 《地层学杂志》2003,27(4):282-288,T001
对近二十年来黑龙江省东部海相侏罗纪—白垩纪沟鞭藻地层资料进行了综合研究 ,首次为该地区建立起侏罗纪—白垩纪沟鞭藻地层序列 ,主要包含 7个组合带 (含 3个高峰带 ) ,其中绥滨地区 Callovian— Valanginian期有 4个带 ;鸡西盆地早白垩世也有 4个带 (其中包括与绥滨地区早白垩世早期同时异相的一个 )。它们自下而上为 :1)绥滨组的 Pareodinia ceratophora- N annoceratopsispellucida组合带 ;　 2 )东荣组下部的 Gonyaulacysta jurassica组合带 (高峰带 ) ;　 3)东荣组上部的 Amphorula delicata组合带 ;　 4 )东荣组最上部的海相 Oligosphaeridium pul-cherrimum组合带 (高峰带 )或鸡西盆地滴道组的微咸水—半咸水的 Vesperopsis didaoensis- L agenorhytis granoru-gosa组合带 ,两者为同时异相关系 ;　 5 )城子河组下部海相层的 Odontochitina operculata- Muderongia tetracantha组合带 (该带可进一步划分出 2个亚组合带 ) ;　 6 )城子河组上部海相层的 Canningia reticulata组合带 ;　 7)穆棱组下段的 Cribroperidinium ?parorthoceras组合带 (高峰带 )。  相似文献   

9.
Dinosaur eggs or fragments are abundant and extensively distributed in China. They can be very informative in biostratigraphic division and correlation of continental strata where other fossils are relatively lacking. Despite remarkable discoveries of vertebrate fossils, particularly dinosaur eggs and skeletons from the middle and Late Cretaceous of both northern and southern China, there is hardly any direct evidence for the ages of the vertebrate-bearing terrestrial deposits. To constrain their depositional ages, here we have obtained SIMS U–Pb zircon ages from the tuffs interbedded with dinosaur egg-bearing sediments from the Laijia and Chichengshan formations of the terrestrial red deposits of the Late Cretaceous in the Tiantai Basin, Zhejiang Province, southeastern China. The SIMS zircon U–Pb ages from the Laijia and Chichengshan formations are about 96–99 Ma (Cenomanian) and 91–94 Ma (Turonian), respectively, providing direct time constraints on the vertebrate and dinosaur egg evolution in the Late Cretaceous as well as a basis for correlation with terrestrial Cretaceous deposits in other regions of southern and northern China.  相似文献   

10.
The studies of past climatic changes form the basis for predicting our future anthropogenic world and are among the most prominent topics in current Earth sciences. Although the Cretaceous is generally considered as a greenhouse period in Earth's history, a number of significant cooling events based on an array of climatic proxies have been identified. Here we present the first data on Berriasian (Ryazanian) glendonite findings from the paleontologically well dated Lower Cretaceous succession of northeastern Siberia. Based on well calibrated Buchia and ammonite biostratigraphy, the stratigraphic interval across which the glendonites occur is restricted to the late Berriasian. Stable carbon isotope (δ13C) values of the studied glendonites clearly suggest the precipitation of ikaite from marine water without any significant contamination from biogenic methane. Our results, when integrated with other available paleoclimatic proxies from elsewhere in the high latitudes, suggest a revision of the initiation of Early Cretaceous cooling in the high latitudes from the Valanginian to the late Berriasian. All known occurrences of Lower Cretaceous glendonites in both the northern and southern hemispheres are reviewed.  相似文献   

11.
The Sinuiju Formation in Paekto-dong, Sinuiju City in the Democratic People's Republic of Korea has yielded Mesozoic nonmarine bivalve fossils, which is the first occurrence of such in the DPRK. Based on these fossil specimens, a new Cretaceous bivalve assemblage, the Arguniella yanshanensis-Sphaerium anderssoni Assemblage is erected. This assemblage includes Arguniella yanshanensis, A. lingyuanensis and Sphaerium anderssoni and can be compared with the Jehol Biota. The age of the Sinuiju Formation is also clarified and on the basis of the bivalves and the presence of a Eosestheria–Ephemeropsis–Lycoptera(E–E–L) assemblage, the formation is not Upper Jurassic, but Lower Cretaceous in age.  相似文献   

12.
Our understanding of latest Cretaceous and earliest Paleogene mammalian evolution is based almost entirely on the dental fossil record. Mammalian postcranial fossils are rare and mostly found as isolated elements in latest Cretaceous and earliest Paleogene vertebrate microfossil assemblages of North America. Although placing these fossils in a tooth-based taxonomic framework is difficult, they can provide insight into locomotor diversity and habitat preference to complement diet reconstructions and diversity estimates from dental fossils. Here, we describe 64 femora of mammals recovered from latest Cretaceous (Lancian) and earliest Paleogene (Puercan) localities in eastern Montana. We sorted these based on morphology and size (morphotypes). In some cases, morphotypes were tentatively assigned to dentally based taxa that are known from these strata.Although our resulting femoral dataset is small relative to the study area's dental dataset, we show several key findings. First, there is a greater morphological diversity of multituberculate femora than previously recognized, especially in the latest Cretaceous sample. In contrast, metatherians, which have a high relative abundance in Lancian Hell Creek Formation dental assemblages, are absent from our postcranial samples; eutherian femora are only present in the Puercan assemblages. Second, we record a minor decrease in morphotype richness across the K–Pg boundary that is associated with an increase in mean specimen size, due to the appearance of a few significantly larger-bodied, immigrant taxa. Among the eutherians, there are two specimens of larger-bodied early Puercan archaic ungulates, a very large specimen of a middle/late Puercan taeniodont, pantodont, or triisodontid, as well as a specimen possibly attributed to a “plesiadapiform” archaic primate. Third, preliminary functional morphologic analyses of the more complete specimens suggest that locomotor diversity increased from mainly arboreal or terrestrial/saltatorial multituberculates in the latest Cretaceous to include a fossorial multituberculate and potentially an arboreal eutherian in the early Paleocene. These patterns parallel those previously reported from a dental dataset and indicate that postcranial data are valuable as an independent means to test hypotheses of taxonomic and ecomorphological diversity across the K–Pg boundary.  相似文献   

13.
U–Pb geochronological studies of igneous rocks of the Crimean Mountains were carried out for the first time. The ages of magma crystallization determined for gabbro–dolerites of the Dzhidair and Pervomaiskii intrusions point to the injection of these rocks during the Middle Jurassic Aalenian–Bajocian stage of magmatism. The Berriasian–Valanginian and Aptian age of sill-like bodies within the mass of volcanogenic–sedimentary rocks presumes the necessity to reconsider the common notion of an exclusively Albian magmatic event during the Cretaceous. High-precision U–Pb dating of magma intrusions allowed us to verify the age of Middle Jurassic magmatism and to distinguish the new Early Cretaceous Berriasian–Valanginian magmatism stage of basic composition.  相似文献   

14.
Lepisosteid fishes are well known from the Upper Cretaceous of Europe, but only by fragmentary remains from some Cenomanian and Campanian–Maastrichtian deposits. Here we report various cranial and postcranial remains of gars, discovered in the Upper Cretaceous (Santonian) Csehbánya Formation of Iharkút (Bakony Mountains, Hungary). These remains represent one of the most diverse assemblages of lepisosteid fish material from Upper Cretaceous continental deposits of Europe. Based on tooth morphology, scale-microstructure and the features of the supracleithrum we refer these remains to the genus Atractosteus. Besides some uncertain remains from the Cenomanian of France and Spain, the Santonian aged fossils from Iharkút represent the oldest undisputable occurrence of the family Lepisosteidae in the European continental Cretaceous. Using tooth crown morphology, the surface microstructure of the ganoid scales and the anatomy of the supracleithrum a review of the Late Cretaceous lepisosteid record suggests the occurrence of both Atractosteus and Lepisosteus in the European archipelago.  相似文献   

15.
Species concept in North American stegosaurs   总被引：1，自引：0，他引：1  
The plated thyreophoran or stegosaurian dinosaur Stegosaurus armatus was named in 1877 by Marsh for fragmentary remains from the Morrison Formation (Upper Jurassic) of Colorado, USA. Subsequent discoveries from the same formation in Wyoming and Colorado (USA) have been assigned to separate stegosaurian genera and species, but most of these are no longer considered valid. More recently, a partial stegosaurian skeleton from Wyoming was named Hesperosaurus mjosi. However, the validity of this genus has been questioned recently, raising the question: how much osteological difference among stegosaur taxa is needed to separate genera from species? The question is examined vis-à-vis species and genus recognition in other dinosaurs, including iguanodonts, lambeosaurine iguanodontids, chasmosaurine ceratopsians, tyrannosaurid theropods, and diplodocid sauropods. The basis for taxonomic distinction is largely philosophical: if the species are morphologically distinct enough, they should be treated as separate genera. Based on these criteria, Hesperosaurus mjosi is a distinct taxon.  相似文献   

16.
Basal iguanodontians (“iguanodontids”) were a successful group of ornithopod dinosaurs that attained a near global distribution by the late Early Cretaceous. Despite their body fossils being known in abundance from the uppermost Jurassic and Lower Cretaceous of the western United States, their remains have never been found in western Canada. With its extensive, terrestrial sedimentary record for the whole of the Early Cretaceous, the expectation is that these dinosaurs would have been present in western Canada. This paper reports the finding of a fossil footprint from the Gladstone Formation in southwestern Alberta that is interpreted to have been made by an iguanodontid. This identification is based on the late Barremian age of the hosting rock, gross footprint details that match the skeletal foot structure of Iguanodon bernissartensis, and similarities to Early Cretaceous dinosaur footprints found elsewhere in the world that are attributed to iguanodontids. This finding fills a noticeable gap in the iguanodontian fossil record, and is consistent with the clade's attainment of global distribution during the Early Cretaceous.  相似文献   

17.
We present a new species of Steinmanella Crickmay from the Valanginian of the Neuquén Basin, west-central Argentina, and at the same time update a Valanginian–earliest Barremian bivalve zonation which is integrated into the local, Chilean and European standard ammonoid zonations. Steinmanella caicayensis sp. nov. presents a moderately inflated shell, a subtriangular outline, well-developed carinae and a straight to moderately convex anterior margin. Steinmanella is very abundant in the Tithonian–Barremian interval in the basin and thus provides an ideal opportunity to perform detailed taxonomic and stratigraphic studies; a former zonation based on these trigonioids is here revised and expanded with a thorough revision of Valanginian occurrences based on new material. Two new zones are proposed, namely the S. quintucoensis and S. caicayensis zones, encompassing Valanginian times. The proposed bivalve zonation encompassing the Valanginian–earliest Barremian time interval can be useful in correlating with other southwestern Gondwanan regions, such as Perú, Chile, South Africa, Tanzania, and India, where Steinmanella has been recorded.  相似文献   

18.
The first partial skeleton of a stegosaurian dinosaur was discovered in a brick pit in Swindon, UK in 1874. Since then, numerous stegosaurian remains have been discovered from Europe, North America, Africa and Asia, and continue to be discovered regularly. Stegosaurs are known from the Middle Jurassic to the Early Cretaceous; no definitive evidence of the clade is known from younger deposits. New discoveries are improving our understanding of stegosaur biology and showing that stegosaurs were more morphologically diverse than was previously realized. A new phylogeny, which includes all valid stegosaurian taxa, largely agrees with previous studies and shows the European Dacentrurinae was sister taxon to Stegosaurus. Poor resolution at the base of Stegosauria is probably due to the fragmentary nature of many of the Chinese taxa.  相似文献   

19.
The 5th meeting of the IUGS Lower Cretaceous Ammonite Working Group (the Kilian Group) held in Ankara, Turkey, 31st August 2013, discussed the Mediterranean ammonite zonation, and its calibration with different ammonite zonal schemes of the Boreal, Austral and Central Atlantic realms. Concerning the standard zonation, that corresponds to the zonal scheme of the West Mediterranean province, some changes have been made on two stages. For the Valanginian, the Busnardoites campylotoxus Zone was abandoned; the upper part of the lower Valanginian is now characterised by the Neocomites neocomiensiformis and Karakaschiceras inostranzewi zones. For the upper Barremian, the former Imerites giraudi Zone is here subdivided into two zones, a lower I. giraudi Zone and an upper Martellites sarasini Zone. The I. giraudi Zone is now subdivided into the I. giraudi and Heteroceras emerici subzones, previously considered as horizons. The current M. sarasini and Pseudocrioceras waagenoides subzones correspond to the lower and upper parts of the M. sarasini Zone, respectively. The Anglesites puzosianum Horizon is kept. The Berriasian, Hauterivian, Aptian and Albian zonal schemes have been discussed but no change was made. The upper Hauterivian zonal scheme of the Georgian (Caucasus) region (East Mediterranean province) has been compared with the standard zonation. Discussions and some attempts at correlations are presented here between the standard zonation and the zonal schemes of different palaeobiogeographical provinces: the North-West European area for the Valanginian and Hauterivian, the Argentinean region for the Berriasian, Valanginian and Hauterivian, and the Mexican area for the Valanginian–Hauterivian and Aptian–lower Albian. The report concludes with some proposals for future work.  相似文献   

20.
Plesiosaur fossils from the uppermost Tithonian (Upper Jurassic) to lower Valanginian (Lower Cretaceous) Purbeck Limestone Group of Dorset, England are important because they constitute a rare record from around the Jurassic-Cretaceous boundary. Where diagnostic, the remains are referred to indeterminate plesiosauroids (Cryptocleidoidea) and represent relatively small animals including a previously undescribed juvenile individual. This observation accords with the lagoonal-lacustrine (with periodic marine influx) depositional setting of the Purbeck Limestone Group strata, a palaeoenvironment that is often associated with juvenile plesiosaur occurrences.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号