鸟类飞行起源问题新思路

目前学术界对于有关鸟类起源与鸟类飞行起源等问题仍存在激烈争论。在关于鸟类飞行起源问题上一直存在两种对立假说：一种是地栖起源说,认为鸟类的飞翔是由鸟类祖先在地面奔跑和跳跃的过程中逐步升腾起飞成功的。此假说通常与鸟类小型兽脚类恐龙起源假说相关联。另一种是树栖起源说,认为鸟类最初的飞行是通过借助树木的高度,先进行滑翔,然后逐步发展,从而产生鸟类特有的振翅飞翔的本领。     

鸟是如何飞上天的

鸟是如何飞上天的周忠和很久以来,人们对于鸟类飞行起源的问题,或者通俗一点讲就是鸟类如何飞上天的问题,存在两种不同的意见。一种观点认为,原始的鸟类通过攀援树木,在下滑翔并逐渐学会了拍翅飞行的本领;另一种观点则认为,鸟类最初的飞行与树无关,原始的鸟类通过...     

飞蜥滑翔的适应性特征及滑翔起源的研究进展

本文综述了飞蜥对滑翔的适应性特征及其滑翔能力起源的研究进展.主要包括翼膜的内部解剖结构、表面覆盖物的特征、飞蜥对翼膜的控制机制、古类蜥蜴滑翔爬行动物的种类及起源等方面,以期借此为今后在该领域的研究提供一定的参考.     

解惑

听说还有会飞的恐龙,那它得长多大的翅膀啊?恐龙大多是不会飞的,不过现在也有证据表明有一些恐龙会滑翔,比如顾氏小盗龙,它的四肢上长有一些羽毛,我们通常俗称为“四翅恐龙”。有化石证据表明这种体型比较小的恐龙会爬树,并能利用树枝间的落差滑翔。这也涉及了鸟类的飞行起源问题,即鸟类是从快速奔跑中开始学会飞行的,还是首先爬树,利用树间高差滑翔开始飞行的。四翅恐龙的翅膀并不大,化石证据表明它们的翼展大约有1米左右。     

早期鸟类的飞行能力与羽毛的起源

关于鸟类飞行的起源问题,与鸟类的起源问题同样重要。这一问题在学术界主要有两种假说：一种是由美国学S．W．Willistong在1879年提出的地栖起源说（疾走起源说）,另一种是美国学O．C．Marsh在1880年提出的树栖起源说。前通常与鸟类兽脚类起源说相联系,而后往往被认为同鸟类槽齿类起源说有关。     

评《鸟类的起源与演化》

(TheOriginandEvolutionofBirds,byAlanFeduccia,1996.YaleUniversityPress.NewHavenandLondon.432pp.534illus.55.)一部新书问世,读者的反应可能褒贬不一,而当书中又恰好涉及众多争论不休的问题时,情况便注定如此。最近,耶鲁人学出版的《鸟类的起源’－。演化》一书,涉及到或许是目前古脊椎动物学中最具争议的一个问题,即鸟类究竟是直接起源于地面奔跑的恐龙还是来自与恐龙共同的祖先——小型的槽齿类爬行动物？就飞行起源而论,是由地面升腾向［还是由树上滑翔而下？一方面,本书刚一问世便已赢得一片赞誉,有位鸟类学家竞声称…     

科学家发现鸟类起源于恐龙的最新证据

鸟类的起源一直是国际古生物学界的热点问题之一,自上个世纪60年代末至70年代初,美国耶鲁大学教授约翰·奥斯罗姆复兴了赫胥黎提出的鸟类兽脚类恐龙起源假说后,鸟类起源的研究取得了巨大的进展,来自世界各地不同地史时期的恐龙和早期鸟类的大量化石证据持续不断地出现,有力地支持着这一假说。1986年美国耶鲁大学教授嘉克斯·高斯特首次用分支系统学的方法系统地分析了鸟类与其他初龙类（一个包括恐龙、翼龙、鳄型动物以及一些绝灭支系的爬行动物类群）的关系,     

被视为恐龙的鸟

尽管于 2 0世纪 2 0年代在亚洲地表层首次发现长有羽毛的恐龙和著名的“龙骨突位点” ,关于鸟类起源的争论仍没有休止。来自化石的证据表明 ,鸟类在进化分支上应归于兽脚类的特殊分支。本文主要阐明完好无损的化石揭示的鸟和非鸟类恐龙的亲密关系和鸟类羽毛及鸟类出现以前的羽毛的起源证据 ,分析体型缩小对飞行进化的重要意义及从新的角度论述鸟类如何飞上了天     

“羽毛”早期演化研究的新进展

自二十世纪60年代末至70年代初,美国耶鲁大学教授约翰·奥斯罗姆复兴了赫胥黎提出的鸟类兽脚类恐龙起源假说后,鸟类起源的研究取得了巨大的进展,这一假说已普遍为人们所接受。1975年,美国古生物学家罗伯特·巴克甚至大胆地宣布：     

鸟类起源与演化百问百答（上）

一、起源篇１ 鸟类起源于恐龙吗 ?目前国际上多数学者已同意鸟类确实起源于一类小型的兽脚类恐龙 ,但仍有一些学者持不同看法。２ “鸟就是恐龙 ,恐龙就是鸟”这句话对吗 ?如果承认鸟类起源于恐龙 ,那么说鸟就是恐龙就相当于说人是哺乳动物 ,从系统关系和分类的角度来讲 ,这句话基本算对 ,但严格来说 ,也不对 ,因为鸟类和恐龙毕竟存在差别正如人和哺乳动物存在很大不同的道理一样 ;但是说恐龙就是鸟则相当于说哺乳动物就是人 ,显然是不对的。３ 鸟类的起源有几大假说 ?历史上关于鸟类的起源 ,主要存在过三种主要的假说 :一是鸟类的恐龙起源…     

Anatomy and histochemistry of spread-wing posture in birds. 3. Immunohistochemistry of flight muscles and the "shoulder lock" in albatrosses

As a postural behavior, gliding and soaring flight in birds requires less energy than flapping flight. Slow tonic and slow twitch muscle fibers are specialized for sustained contraction with high fatigue resistance and are typically found in muscles associated with posture. Albatrosses are the elite of avian gliders; as such, we wanted to learn how their musculoskeletal system enables them to maintain spread-wing posture for prolonged gliding bouts. We used dissection and immunohistochemistry to evaluate muscle function for gliding flight in Laysan and Black-footed albatrosses. Albatrosses possess a locking mechanism at the shoulder composed of a tendinous sheet that extends from origin to insertion throughout the length of the deep layer of the pectoralis muscle. This fascial "strut" passively maintains horizontal wing orientation during gliding and soaring flight. A number of muscles, which likely facilitate gliding posture, are composed exclusively of slow fibers. These include Mm. coracobrachialis cranialis, extensor metacarpi radialis dorsalis, and deep pectoralis. In addition, a number of other muscles, including triceps scapularis, triceps humeralis, supracoracoideus, and extensor metacarpi radialis ventralis, were found to have populations of slow fibers. We believe that this extensive suite of uniformly slow muscles is associated with sustained gliding and is unique to birds that glide and soar for extended periods. These findings suggest that albatrosses utilize a combination of slow muscle fibers and a rigid limiting tendon for maintaining a prolonged, gliding posture.     

Optimal flight behavior of soaring migrants: a case study of migrating steppe buzzards, Buteo buteo vulpinus

This article presents tests of the theoretical predictions onoptimal soaring and gliding flight of large, diurnal migrantsusing Pennycuick's program 2 for "bird flight performance."Predictions were compared with 141 observed flight paths ofmigrating steppe buzzards, Buteo buteo vulpinus. Calculationsof cross-country speed relative to the air included bird's airspeedsand sinking rates in interthermal gliding and climbing ratesin thermal circling. Steppe buzzards adjusted interthermal glidingairspeed . according to their actual climbing rate in thermalcircling. By optimizing their gliding airspeed, the birds maximizedtheir crosscountry performance relative to the air. Despitethis general agreement with the model, there was much scatterin the data, for the model neglects horizontal winds and updraftsduring the gliding phase. Lower sinking rates due to updraftsduring the gliding phases allowed many birds to achieve highercross-country speeds than predicted. In addition, birds reactedto different wind directions and speeds: in side and opposingwinds, the steppe buzzards compensated for wind displacementduring soaring and increased their gliding airspeed with decreasingtailwind component Nevenheless, cross-country speed relativeto the ground, which is the important measure for a migratorybird, was still higher under following winds. This study showsthat Pennycuick's program 2 provides reliable predictions onoptimal soaring and gliding behavior using realistic assumptionsand constants in the model, but a great deal of variation aroundthe mean is generated by factors not included in the model     

A new stem-neopterygian fish from the Middle Triassic of China shows the earliest over-water gliding strategy of the vertebrates

Flying fishes are extraordinary aquatic vertebrates capable of gliding great distances over water by exploiting their enlarged pectoral fins and asymmetrical caudal fin. Some 50 species of extant flying fishes are classified in the Exocoetidae (Neopterygii: Teleostei), which have a fossil record no older than the Eocene. The Thoracopteridae is the only pre-Cenozoic group of non-teleosts that shows an array of features associated with the capability of over-water gliding. Until recently, however, the fossil record of the Thoracopteridae has been limited to the Upper Triassic of Austria and Italy. Here, we report the discovery of exceptionally well-preserved fossils of a new thoracopterid flying fish from the Middle Triassic of China, which represents the earliest evidence of an over-water gliding strategy in vertebrates. The results of a phylogenetic analysis resolve the Thoracopteridae as a stem-group of the Neopterygii that is more crown-ward than the Peltopleuriformes, yet more basal than the Luganoiiformes. As the first record of the Thoracopteride in Asia, this new discovery extends the geographical distribution of this group from the western to eastern rim of the Palaeotethys Ocean, providing new evidence to support the Triassic biological exchanges between Europe and southern China. Additionally, the Middle Triassic date of the new thoracopterid supports the hypothesis that the re-establishment of marine ecosystems after end-Permian mass extinction is more rapid than previously thought.     

Gliding flight in the American Kestrel (Falco sparverius): An electromyographic study

Electromyographic (EMG) activity was studied in American Kestrels (Falco sparverius) gliding in a windtunnel tilted to 8 degrees below the horizontal. Muscle activity was observed in Mm. biceps brachii, triceps humeralis, supracoracoideus, and pectoralis, and was absent in M. deltoideus major and M. thoracobrachialis (region of M. pectoralis). These active muscles are believed to function in holding the wing protracted and extended during gliding flight. Quantification of the EMG signals showed a lower level of activity during gliding than during flapping flight, supporting the idea that gliding is a metabolically less expensive form of locomotion than flapping flight. Comparison with the pectoralis musculature of specialized gliding and soaring birds suggests that the deep layer of the pectoralis is indeed used during gliding flight and that the slow tonic fibers found in soaring birds such as vultures represents a specialization for endurant gliding. It is hypothesized that these slow fibers should be present in the wing muscles that these birds use for wing protraction and extension, in addition to the deep layer of the pectoralis. © 1993 Wiley-Liss, Inc.     

The gliding speed of migrating birds: slow and safe or fast and risky?

Aerodynamic theory postulates that gliding airspeed, a major flight performance component for soaring avian migrants, scales with bird size and wing morphology. We tested this prediction, and the role of gliding altitude and soaring conditions, using atmospheric simulations and radar tracks of 1346 birds from 12 species. Gliding airspeed did not scale with bird size and wing morphology, and unexpectedly converged to a narrow range. To explain this discrepancy, we propose that soaring‐gliding birds adjust their gliding airspeed according to the risk of grounding or switching to costly flapping flight. Introducing the Risk Aversion Flight Index (RAFI, the ratio of actual to theoretical risk‐averse gliding airspeed), we found that inter‐ and intraspecific variation in RAFI positively correlated with wing loading, and negatively correlated with convective thermal conditions and gliding altitude, respectively. We propose that risk‐sensitive behaviour modulates the evolution (morphology) and ecology (response to environmental conditions) of bird soaring flight.     

Mechanics of gliding in birds with special reference to the influence of the ground effect

A model of the mechanics of gliding without loss of altitude (horizontal gliding) is developed. The model can be employed to assess the influence of the principal drag components (induced, profile and parasite drag), choice of initial and final glide velocities and height above the ground on glide distance. For birds gliding near to the ground the ground effect acts to decrease the induced drag and increase the lift to drag ratio of the wings. Minimum drag speed is reduced for birds gliding near to the ground. The model is applied to the gliding flight of the black skimmer (Rhyncops nigra). Glide distances for given initial and final velocities are significantly increased in the influence of the ground effect over out of ground effect values.     

Gravity-defying Behaviors: Identifying Models for Protoaves

Most current phylogenetic hypotheses based upon cladistic methodologyassert that birds are the direct descendants of derived maniraptorantheropod dinosaurs, and that the origin of avian flight necessarilydeveloped within a terrestrial context (i.e., from the "groundup"). Most theoretical aerodynamic and energetic models or chronologicallyappropriate fossil data do not support these hypotheses forthe evolution of powered flight. The more traditional modelfor the origin of flight derives birds from among small arborealearly Mesozoic archosaurs ("thecodonts"). According to thismodel, protoavian ancestors developed flight in the trees viaa series of intermediate stages, such as leaping, parachuting,gliding, and flapping. This model benefits from the assemblageof living and extinct arboreal vertebrates that engage in analogousnon-powered aerial activities using elevation as a source ofgravitational energy. Recent reports of "feathered theropods"notwithstanding, the evolution of birds from any known groupof maniraptoran theropods remains equivocal.     

Phylogeny of families in the Pectinoidea (Mollusca: Bivalvia): importance of the fossil record

The Triassic fossil record points to the monophyly of the Pectinoidea (scallops), all members of which have a triangular resilium with a nonmineralized medial core that functions below the hinge line. The elastic properties of this resilium in extant taxa predict that the initial adaptation of the Pectinoidea was to swimming. This is indeed corroborated by the shell form of Pernopecten , the earliest known pectinoidean genus, which ranged from late Devonian to earliest Triassic. The new family Entolioididae, a largely Triassic group, provides the missing link between the Pernopectinidae and the families Propeamussiidae, Entoliidae, and Pectinidae, all of which originated by the Middle Triassic and survive to the present day. A new Triassic genus Filamussium shows that the Propeamussiidae originated from the Entolioididae, not directly from the Pernopectinidae as previously supposed. Evidence from morphology, the fossil record, and molecular genetics indicates that the family Spondylidae originated in the Middle Jurassic from an ancestor within the Pectinidae, possibly the genus Spondylopecten , which was already present in the Late Triassic. Journal compilation © 2006 The Linnean Society of London, Zoological Journal of the Linnean Society , 2006, 148 , 313–342. No claim to original US government works     

Soaring across continents: decision‐making of a soaring migrant under changing atmospheric conditions along an entire flyway

Thermal soaring birds reduce flight‐energy costs by alternatingly gaining altitude in thermals and gliding across the earth's surface. To find out how soaring migrants adjust their flight behaviour to dynamic atmospheric conditions across entire migration routes, we combined optimal soaring migration theory with high‐resolution GPS tracking data of migrating honey buzzards Pernis apivorus and wind data from a global numerical atmospheric model. We compared measurements of gliding air speeds to predictions based on two distinct behavioural benchmarks for thermal soaring flight. The first being a time‐optimal strategy whereby birds alter their gliding air speeds as a function of climb rates to maximize cross‐country air speed over a full climb– glide cycle (V_opt). The second a risk‐averse energy‐efficient strategy at which birds alter their gliding air speed in response to tailwinds/headwinds to maximize the distance travelled in the intended direction during each glide phase (V_bgw). Honey buzzards were gliding on average 2.05 ms^{– 1} slower than V_opt and 3.42 ms^{– 1} faster than V_bgw while they increased air speeds with climb rates and reduced air speeds in tailwinds. They adopted flexible flight strategies gliding mostly near V_bgw under poor soaring conditions and closer to V_opt in good soaring conditions. Honey buzzards most adopted a time‐optimal strategy when crossing the Sahara, and at the onset of spring migration, where and when they met with the best soaring conditions. The buzzards nevertheless glided slower than V_opt during most of their journeys, probably taking time to navigate, orientate and locate suitable thermals, especially in areas with poor thermal convection. Linking novel tracking techniques with optimal migration models clarifies the way birds balance different tradeoffs during migration.     

Marked colour divergence in the gliding membranes of a tropical lizard mirrors population differences in the colour of falling leaves

Populations of the Bornean gliding lizard, Draco cornutus, differ markedly in the colour of their gliding membranes. They also differ in local vegetation type (mangrove forest versus lowland rainforest) and consequently, the colour of falling leaves (red and brown/black in mangrove versus green, brown and black in rainforest). We show that the gliding membranes of these lizards closely match the colours of freshly fallen leaves in the local habitat as they appear to the visual system of birds (their probable predators). Furthermore, gliding membranes more closely resembled colours of local fallen leaves than standing foliage or fallen leaves in the other population''s habitat. This suggests that the two populations have diverged in gliding membrane coloration to match the colours of their local falling leaves, and that mimicking falling leaves is an adaptation that functions to reduce predation by birds.