共查询到20条相似文献，搜索用时 15 毫秒
1.
Clarke JA Ksepka DT Salas-Gismondi R Altamirano AJ Shawkey MD D'Alba L Vinther J DeVries TJ Baby P 《Science (New York, N.Y.)》2010,330(6006):954-957
Penguin feathers are highly modified in form and function, but there have been no fossils to inform their evolution. A giant penguin with feathers was recovered from the late Eocene (~36 million years ago) of Peru. The fossil reveals that key feathering features, including undifferentiated primary wing feathers and broad body contour feather shafts, evolved early in the penguin lineage. Analyses of fossilized color-imparting melanosomes reveal that their dimensions were similar to those of non-penguin avian taxa and that the feathering may have been predominantly gray and reddish-brown. In contrast, the dark black-brown color of extant penguin feathers is generated by large, ellipsoidal melanosomes previously unknown for birds. The nanostructure of penguin feathers was thus modified after earlier macrostructural modifications of feather shape linked to aquatic flight. 相似文献
2.
Normile D 《Science (New York, N.Y.)》2000,288(5472):1721
Last week, Chinese scientists presented evidence from a new specimen dug up in Liaoning Province that they say strengthens the case for the bird-dinosaur link. The finding, one of several fossils displayed at a meeting here, is the third known specimen of a strange creature known as Caudipteryx which, unlike any other known dinosaur fossil, shows the unmistakable imprints of feathers. The researcher who described the new specimen at the meeting has identified 16 characteristics of the new fossil that are more similar to dinosaurs than to early birds, reinforcing the views of most Western scientists. 相似文献
3.
Jones TD Ruben JA Martin LD Kurochkin EN Feduccia A Maderson PF Hillenius WJ Geist NR Alifanov V 《Science (New York, N.Y.)》2000,288(5474):2202-2205
Longisquama insignis was an unusual archosaur from the Late Triassic of central Asia. Along its dorsal axis Longisquama bore a series of paired integumentary appendages that resembled avian feathers in many details, especially in the anatomy of the basal region. The latter is sufficiently similar to the calamus of modern feathers that each probably represents the culmination of virtually identical morphogenetic processes. The exact relationship of Longisquama to birds is uncertain. Nevertheless, we interpret Longisquama's elongate integumentary appendages as nonavian feathers and suggest that they are probably homologous with avian feathers. If so, they antedate the feathers of Archaeopteryx, the first known bird from the Late Jurassic. 相似文献
4.
Stokstad E 《Science (New York, N.Y.)》2000,288(5474):2124-2125
On page 2202, researchers describe the 220-million-year-old Longisquama insignis, a squat, mouse-sized reptile with at least six vanelike appendages up to 12 centimeters long sprouting from its spine. The authors argue that the appendages are feathers much like those of modern birds; outside the paper, they have touted the fossil as "an ideal bird ancestor." That conclusion has infuriated paleontologists--not just because it challenges the prevalent theory that birds evolved from theropod dinosaurs, but because they say it does so in an unscientific way. 相似文献
5.
The fossil record of early feathers has relied on carbonized compressions that lack fine structural detail. Specimens in amber are preserved in greater detail, but they are rare. Late Cretaceous coal-rich strata from western Canada provide the richest and most diverse Mesozoic feather assemblage yet reported from amber. The fossils include primitive structures closely matching the protofeathers of nonavian dinosaurs, offering new insights into their structure and function. Additional derived morphologies confirm that plumage specialized for flight and underwater diving had evolved in Late Cretaceous birds. Because amber preserves feather structure and pigmentation in unmatched detail, these fossils provide novel insights regarding feather evolution. 相似文献
6.
Charig AJ Greenaway F Milner AC Walker CA Whybrow PJ 《Science (New York, N.Y.)》1986,232(4750):622-626
Archaeopteryx lithographica might be regarded as the most important zoological species known, fossil or recent. Its importance lies not in that its transitional nature is unique-there are many such transitional forms at all taxonomic levels-but in the fact that it is an obvious and comprehensible example of organic evolution. There have been recent allegations that the feather impressions on Archaeopteryx are a forgery. In this report, proof of authenticity is provided by exactly matching hairline cracks and dendrites on the feathered areas of the opposing slabs, which show the absence of the artificial cement layer into which modern feathers could have been pressed by a forger. 相似文献
7.
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
8.
朱鹮羽毛的扫描电镜观察 总被引：5，自引：0，他引：5
用扫描电子显微镜对朱鹮(Nipponia nippon)不同部位羽毛进行了超微结构观察。结果表明:起飞翔作用的飞羽和尾羽主要由有钩羽小枝和无钩羽小枝构成;有钩羽小枝和无钩羽小枝相互啮合形成坚实的羽面来减少飞行阻力。组成羽冠的颈羽有着特殊的特点,先端羽小枝两侧全部为无钩羽小枝,而后沿着羽轴向根部逐渐变化,出现有钩羽小枝。尾羽的有钩羽小枝中的小钩数绝大多数为4个,纤毛为6对;飞羽的有钩羽小枝中的小钩数绝大多数为5个,少部分为6个,纤毛为6对;颈羽的有钩羽小枝小钩数绝大多数为4个,纤毛为5对。朱鹮的各羽小枝的腹齿数变化较大。羽轴及羽枝轴无明显特征,髓质层由多孔的髓腔构成。 相似文献
9.
本文研究５种禽类羽毛氨基酸组分和含量分析的差异．新浦东鸡的副羽含量最高达９０．１％；居古拉火鸡最低在７１％。１４种羽毛的氨基酸平均含量为８０％。从氨基酸组分看，丝氨酸，谷氨酸和亮氨酸较高。而赖氨酸，组氨酸和甲硫氨酸均较低，这与已发表的文献一致［３］。 相似文献
10.
猛禽非损伤性取样的性别分子鉴定方法 总被引：1，自引：0，他引：1
利用性染色体上CHD基因的P2/P8和2550F/2718R两对引物及微卫星位点(NVHfp102),对多种猛禽通过非损伤性取样进行性别分子鉴定研究。结果显示:2550F/2718R引物适用于隼形目脱落的有羽根羽毛和无羽根的不完整羽毛,拔取标本的羽毛可以进行鉴定尝试,适用于鸮形目脱落的有羽根羽毛,脱落的无羽根不完整羽毛和拔取标本的羽毛不必进行鉴定尝试;利用P2/P8引物进行非变性聚丙烯酰胺凝胶电泳性别鉴定适用于猛禽脱落的无羽根不完整羽毛和拔取的标本羽毛;微卫星位点(NVHfp102)适用于隼科鸟类各种样本。 相似文献
11.
Watson GE 《Science (New York, N.Y.)》1963,139(3549):50-51
During natural molt in many birds, feathers of the old generation are passively pushed out of the follicles attached to the tips of the sheaths of incoming feathers. 相似文献
12.
Devonian brachiopods, identifiable at the generic level, have been recovered from calc-silicate rocks more intensely metamorphosed and metasomatized than any other known fossil occurrence. The fossils are a key stratigraphic link between granulite facies rocks of central New Hampshire and fossiliferous rocks of western New Hampshire and Maine. 相似文献
13.
Paul GS 《Science (New York, N.Y.)》2010,330(6002):320; author reply 320
Nudds and Dyke (Reports, 14 May 2010, p. 887) compared the rachis diameters of the primary feathers of Archaeopteryx and Confuciusornis to those of modern birds and found that the primary feathers of these two basal birds were too weak to support sustained flight. Our measurements of Confuciusornis specimens suggest that their conclusions need to be further evaluated. 相似文献
14.
te Welscher P Zuniga A Kuijper S Drenth T Goedemans HJ Meijlink F Zeller R 《Science (New York, N.Y.)》2002,298(5594):827-830
Distal limb development and specification of digit identities in tetrapods are under the control of a mesenchymal organizer called the polarizing region. Sonic Hedgehog (SHH) is the morphogenetic signal produced by the polarizing region in the posterior limb bud. Ectopic anterior SHH signaling induces digit duplications and has been suspected as a major cause underlying congenital malformations that result in digit polydactyly. Here, we report that the polydactyly of Gli3-deficient mice arises independently of SHH signaling. Disruption of one or both Gli3 alleles in mouse embryos lacking Shh progressively restores limb distal development and digit formation. Our genetic analysis indicates that SHH signaling counteracts GLI3-mediated repression of key regulator genes, cell survival, and distal progression of limb bud development. 相似文献
15.
The identities of the digits of the avian forelimb are disputed. Whereas paleontological findings support the position that the digits correspond to digits one, two, and three, embryological evidence points to digit two, three, and four identities. By using transplantation and cell-labeling experiments, we found that the posteriormost digit in the wing does not correspond to digit four in the hindlimb; its progenitor segregates early from the zone of polarizing activity, placing it in the domain of digit three specification. We suggest that an avian-specific shift uncouples the digit anlagen from the molecular mechanisms that pattern them, resulting in the imposition of digit one, two, and three identities on the second, third, and fourth anlagens. 相似文献
16.
During courtship flights, males of some hummingbird species produce diverse sounds with tail feathers of varying shapes. We show that these sounds are produced by air flowing past a feather, causing it to aeroelastically flutter and generate flutter-induced sound. Scanning laser doppler vibrometery and high-speed video of individual feathers of different sizes and shapes in a wind tunnel revealed multiple vibratory modes that produce a range of acoustic frequencies and harmonic structures. Neighboring feathers can be aerodynamically coupled and flutter either at the same frequency, resulting in sympathetic vibrations that increase loudness, or at different frequencies, resulting in audible interaction frequencies. Aeroelastic flutter is intrinsic to stiff airfoils such as feathers and thus explains tonal sounds that are common in bird flight. 相似文献
17.
Fossil burrows within newly recognized buried soils in the Late Ordovician Juniata Formation, near Potters Mills in central Pennsylvania, represent the oldest reported nonmarine trace fossils. They are thought to have been an original part of the soil because their greater density toward the top of the paleosols corresponds with mineralogical, microstructural, and chemical changes attributed to ancient weathering and because about half the burrows are encrusted with nodular carbonate, interpreted as caliche. Associated fossil caliche, the size distribution of the burrows, and their W-shaped backfills are evidence that the burrows may have been excavated by bilaterally symmetrical organisms that grew in well-defined growth increments and were able to withstand desiccation. Among well-known soil organisms, millipedes are burrowing animals that satisfy these requirements, but have a fossil record not quite this old. This trace fossil evidence for animals on land, together with recent palynological evidence for land plants of a bryophytic grade of evolution during Late Ordovician time, are indications of terrestrial ecosystems of slightly greater antiquity and complexity than hitherto suspected. 相似文献
18.
Some nonavian theropod dinosaurs were at least partially covered in feathers or filamentous protofeathers. However, a complete understanding of feather distribution among theropod dinosaurs is limited because feathers are typically preserved only in lagerst?tten like that of Solnhofen, Germany or Liaoning, China. Such deposits possess clear taphonomic biases toward small-bodied animals, limiting our knowledge regarding feather presence in larger members of feathered clades. We present direct evidence of feathers in Velociraptor mongoliensis based on the presence of quill knobs on the posterior forearm. This report of secondaries in a larger-bodied, derived, and clearly flightless member of a nonavian theropod clade represented by feathered relatives is a substantial contribution to our knowledge of the evolution of feathers. 相似文献
19.
Numerous saturated and aromatic hydrocarbons, but not polar compounds, originating from plants and microorganisms (biomarkers) have been reported in sediments, coals, and petroleum. Here we describe natural product terpenoids found in two fossil conifers, Taxodium balticum (Eocene) and Glyptostrobus oregonensis (Miocene). A similar terpenoid pattern is also observed in extant Taxodium distichum. The preservation of characteristic terpenoids (unaltered natural products) in the fossil conifers supports their systematic assignment to the Cypress family (Cupressaceae sensu lato). The results also show that fossil conifers can contain polar terpenoids, which are valuable markers for (paleo)chemosystematics and phylogeny. 相似文献
20.
为了确定饲喂鹅绒助长剂的鹅适宜首次拔毛时间和上下次拔毛时间间隔,利用对照组与试验组鹅各10只,分别从70日龄和第1次拔毛后的第36 d 开始,直至80日龄和首次拔毛后的第40 d,每隔1 d 观测各鹅颈下1/3、胸腹部和背部的血管毛根数和羽根血肉附着情况.结果表明,观测至80日龄和首次拔毛后第40 d 时,所测处,试验组无可见血管毛和血肉附着的羽根,而对照组却两者均存在.因此,饲喂鹅绒助长剂,进行养鹅拔毛时,适宜的首次拔毛时间是第80日龄,上下次拔毛的时间间隔为40 d. 相似文献