共查询到20条相似文献，搜索用时 15 毫秒
1.
Gabunia L Vekua A Lordkipanidze D Swisher CC Ferring R Justus A Nioradze M Tvalchrelidze M Antón SC Bosinski G Jöris O Lumley MA Majsuradze G Mouskhelishvili A 《Science (New York, N.Y.)》2000,288(5468):1019-1025
Archaeological excavations at the site of Dmanisi in the Republic of Georgia have uncovered two partial early Pleistocene hominid crania. The new fossils consist of a relatively complete cranium and a second relatively complete calvaria from the same site and stratigraphic unit that yielded a hominid mandible in 1991. In contrast with the uncertain taxonomic affinity of the mandible, the new fossils are comparable in size and morphology with Homo ergaster from Koobi Fora, Kenya. Paleontological, archaeological, geochronological, and paleomagnetic data from Dmanisi all indicate an earliest Pleistocene age of about 1.7 million years ago, supporting correlation of the new specimens with the Koobi Fora fossils. The Dmanisi fossils, in contrast with Pleistocene hominids from Western Europe and Eastern Asia, show clear African affinity and may represent the species that first migrated out of Africa. 相似文献
2.
Hand of Paranthropus robustus from Member 1, Swartkrans: fossil evidence for tool behavior 总被引：1，自引：0，他引：1
R L Susman 《Science (New York, N.Y.)》1988,240(4853):781-784
New hand fossils from Swartkrans (dated at about 1.8 million years ago) indicate that the hand of Paranthropus robustus was adapted for precision grasping. Functional morphology suggests that Paranthropus could have used tools, possibly for plant procurement and processing. The new fossils further suggest that absence of tool behavior was not responsible for the demise of the "robust" lineage. Conversely, these new fossils indicate that the acquisition of tool behavior does not account for the emergence and success of early Homo. 相似文献
3.
Recent collections from plant-bearing deposits of Cenomanian age in central Kansas have yielded angiosperm axes with helically arranged, seed-bearing, conduplicate carpels. Large leaves associated with these fruits are thought to represent parts of the same kind of plant because the leaves and fruits are the only plant fossils at this locality to have distinctive, morphologically identical, yellow bodies within their carbonaceous remains. These fossils provide a rare opportunity to study the morphology of an ancient angiosperm and illustrate the antiquity of certain features considered primitive by comparative angiosperm morphologists. 相似文献
4.
Fossilized nuclei and germination structures identify Ediacaran "animal embryos" as encysting protists 总被引：1，自引：0，他引：1
Huldtgren T Cunningham JA Yin C Stampanoni M Marone F Donoghue PC Bengtson S 《Science (New York, N.Y.)》2011,334(6063):1696-1699
Globular fossils showing palintomic cell cleavage in the Ediacaran Doushantuo Formation, China, are widely regarded as embryos of early metazoans, although metazoan synapomorphies, tissue differentiation, and associated juveniles or adults are lacking. We demonstrate using synchrotron-based x-ray tomographic microscopy that the fossils have features incompatible with multicellular metazoan embryos. The developmental pattern is comparable with nonmetazoan holozoans, including germination stages that preclude postcleavage embryology characteristic of metazoans. We conclude that these fossils are neither animals nor embryos. They belong outside crown-group Metazoa, within total-group Holozoa (the sister clade to Fungi that includes Metazoa, Choanoflagellata, and Mesomycetozoea) or perhaps on even more distant branches in the eukaryote tree. They represent an evolutionary grade in which palintomic cleavage served the function of producing propagules for dispersion. 相似文献
5.
Thiede J 《Science (New York, N.Y.)》1981,211(4489):1422-1424
Upper Mesozoic and Cenozoic pelagic sediments in the central Pacific Ocean contain occasional horizons with reworked and displaced fossils produced by organisms that once lived in neritic shallow-water environments. The flux of neritic fossils was restricted to eight intervals of low eustatic sea level during Late Mesozoic and Cenozoic times. They were eroded from shoals along the flanks of volcanic highs which often supported tropical islands and which since then have subsided. 相似文献
6.
Cycads: fossil evidence of late paleozoic origin 总被引：1，自引：0，他引：1
Mamay SH 《Science (New York, N.Y.)》1969,164(3877):295-296
Plant fossils from Lower Permian strata of the southwestern United States have been interpreted as cycadalean megasporophylls. They are evidently descended from spermopterid elements of the Pennsylvanian Taeniopteris complex; thus the known fossil history of the cycads is extended from the Late Triassic into the late Paleozoic. Possible implications of the Permian fossils toward evolution of the angiosperm carpel are considered. 相似文献
7.
The Stirling Range Formation of southwestern Australia contains discoidal impressions and trace-like fossils in tidal sandstones. The various disks have previously been linked to the Ediacaran biota, younger than 600 million years old. From this unit, we report U-Th-Pb geochronology of detrital zircon and monazite, as well as low-grade metamorphic monazite, constraining the depositional age to between 2016 +/- 6 and 1215 +/- 20 million years old. Although nonbiological origins for the discoidal impressions cannot be completely discounted, the structures resembling trace fossils clearly have a biological origin and suggest the presence of vermiform, mucus-producing, motile organisms. 相似文献
8.
Beauchamp B Harrison JC Nassichuk WW Krouse HR Eliuk LS 《Science (New York, N.Y.)》1989,244(4900):53-56
Lower Cretaceous cold-seep fossil assemblages have been found in the Canadian Arctic Archipelago. Serpulid worm tubes and bivalves are most abundant in these communities; in contrast, fossils are scarce in the surrounding strata. The fossils are contained in an isotopically light (delta(13)C = -25 to -50 per mil) carbonate rock groundmass that is interpreted to have formed from bacterial oxidation of methane. The rocks were deposited at intermediate depth (相似文献
9.
Wogelius RA Manning PL Barden HE Edwards NP Webb SM Sellers WI Taylor KG Larson PL Dodson P You H Da-qing L Bergmann U 《Science (New York, N.Y.)》2011,333(6049):1622-1626
Well-preserved fossils of pivotal early bird and nonavian theropod species have provided unequivocal evidence for feathers and/or downlike integuments. Recent studies have reconstructed color on the basis of melanosome structure; however, the chemistry of these proposed melanosomes has remained unknown. We applied synchrotron x-ray techniques to several fossil and extant organisms, including Confuciusornis sanctus, in order to map and characterize possible chemical residues of melanin pigments. Results show that trace metals, such as copper, are present in fossils as organometallic compounds most likely derived from original eumelanin. The distribution of these compounds provides a long-lived biomarker of melanin presence and density within a range of fossilized organisms. Metal zoning patterns may be preserved long after melanosome structures have been destroyed. 相似文献
10.
Glomalean fungi from the Ordovician 总被引：3，自引：0，他引：3
Fossilized fungal hyphae and spores from the Ordovician of Wisconsin (with an age of about 460 million years) strongly resemble modern arbuscular mycorrhizal fungi (Glomales, Zygomycetes). These fossils indicate that Glomales-like fungi were present at a time when the land flora most likely only consisted of plants on the bryophytic level. Thus, these fungi may have played a crucial role in facilitating the colonization of land by plants, and the fossils support molecular estimates of fungal phylogeny that place the origin of the major groups of terrestrial fungi (Ascomycota, Basidiomycota, and Glomales) around 600 million years ago. 相似文献
11.
Living organisms are known to create structures in ancient rocks that are indigenous but not primary and that have been mistaken for fossils. Examination of burrows recently reported as fossils from 10(9)-year-old sedimentary rocks indicates that they are not the same age as the rocks but were probably made by termites working down after water. The burrows are partially filled with material from a modern lateritic surface from which they descend into steeply dipping, decomposed silt-stones of the Zambian Copperbelt. In fact, no authentic record of Metazoa that are demonstrably coeval with rocks older than 680 million years is known. 相似文献
12.
13.
The fossil record offers the only direct evidence of extinct life and thus has figured prominently in considerations of evolutionary patterns. But the incomplete nature of the fossil record has also been emphasized in arguments that fossils play only a secondary role in the recovery of phylogenetic histories based on extant taxa. Although these criticisms recently have been countered, there is no general understanding of the correspondence between the fossil record and phylogeny. An empirical survey of recently published studies suggests no basis for assuming that the stratigraphic occurrence of fossils always provides a precise reflection of phylogeny. Nevertheless, our survey of a sample of taxa shows a tendency for positive correlation between age and clade rank and, hence, a degree of correspondence between phylogenetic pattern and the paleontologic record. 相似文献
14.
Pecoits E Konhauser KO Aubet NR Heaman LM Veroslavsky G Stern RA Gingras MK 《Science (New York, N.Y.)》2012,336(6089):1693-1696
Based on molecular clocks and biomarker studies, it is possible that bilaterian life emerged early in the Ediacaran, but at present, no fossils or trace fossils from this time have been reported. Here we report the discovery of the oldest bilaterian burrows in shallow-water glaciomarine sediments from the Tacuarí Formation, Uruguay. Uranium-lead dating of zircons in cross-cutting granite dykes constrains the age of these burrows to be at least 585 million years old. Their features indicate infaunal grazing activity by early eumetazoans. Active backfill within the burrow, an ability to wander upward and downward to exploit shallowly situated sedimentary laminae, and sinuous meandering suggest advanced behavioral adaptations. These findings unite the paleontological and molecular data pertaining to the evolution of bilaterians, and link bilaterian origins to the environmental changes that took place during the Neoproterozoic glaciations. 相似文献
15.
McKenzie KG 《Science (New York, N.Y.)》1967,155(3765):1005
New ostracod "living fossils" have been discovered in samples of Recent marine sediment collected from several Pacific islands. The finds include a male anatomy having several primitive features which, in conjunction with primitive features in the shell, necessitate reconsideration of current opinions on the phylogeny of freshwater ostracods. 相似文献
16.
Silurian outcrops, not previously recorded from central Texas, have been identified from the Llano uplift, where they occur in collapse structures within the Lower Ordovician Honeycut Formation of the Ellenburger Group. The formation is a pinkish-gray granular limestone, contains fossils of probable Wenlock age, and is named the Starcke Limestone. 相似文献
17.
Soft-bodied and lightly sclerotized Burgess shale fossils have been found at more than a dozen new localities in an area extending for 20 kilometers along the front of the Cathedral Escarpment in the Middle Cambrian Stephen Formation of the Canadian Rockies. Five different fossil assemblages from four stratigraphic levels have been recognized. These assemblages represent distinct penecontemporaneous marine communities that together make up a normal fore-reef faunal complex. 相似文献
18.
Magnetostratigraphic correlation of the Eureka Sound Formation in the Canadian high Arctic reveals profound difference between the time of appearance of fossil land plants and vertebrates in the Arctic and in mid-northern latitudes. Latest Cretaceous plant fossils in the Arctic predate mid-latitude occurrences by as much as 18 million years, while typical Eocene vertebrate fossils appear some 2 to 4 million years early. 相似文献
19.
Jackson TA 《Science (New York, N.Y.)》1967,155(3765):1003-1005
Fossil actinomycetes and other bacteria have been found in sulfide minerals from "varved" argillites in the middle Precambrian Cobalt Series of Canada. The fossils consist of branched and unbranched nonseptate hyphae and chains of rod-shaped cells. The presence of actinomycetes is consistent with the theory that the argillites are lacustrine desposits. 相似文献
20.
Vekua A Lordkipanidze D Rightmire GP Agusti J Ferring R Maisuradze G Mouskhelishvili A Nioradze M De Leon MP Tappen M Tvalchrelidze M Zollikofer C 《Science (New York, N.Y.)》2002,297(5578):85-89
Another hominid skull has been recovered at Dmanisi (Republic of Georgia) from the same strata in which hominid remains have been reported previously. The Dmanisi site dated to approximately 1.75 million years ago has now produced craniofacial portions of several hominid individuals, along with many well-preserved animal fossils and quantities of stone artifacts. Although there are certain anatomical differences among the Dmanisi specimens, the hominids do not clearly represent more than one taxon. We assign the new skull provisionally to Homo erectus (=ergaster). The Dmanisi specimens are the most primitive and small-brained fossils to be grouped with this species or any taxon linked unequivocally with genus Homo and also the ones most similar to the presumed habilis-like stem. We suggest that the ancestors of the Dmanisi population dispersed from Africa before the emergence of humans identified broadly with the H. erectus grade. 相似文献