DOCSLIB.ORG

PDF Download

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
PDF Download Commentary The Auk 120(2):550–561, 2003 ARE CURRENT CRITIQUES OF THE THEROPOD ORIGIN OF BIRDS SCIENCE? REBUTTAL TO FEDUCCIA (2002) RICHARD O. PRUM1 Department of Ecology and Evolutionary Biology, and Natural History Museum, University of Kansas, Lawrence, Kansas 66045, USA INMYPerspectives in Ornithology essay (Prum unknown early archosaurian ancestor and are 2002), I advocated that all ornithologists should unrelated to theropod dinosaurs. be excited about research on the theropod origin Rather than specifi cally counter the problems of birds. Although I did address some criticisms with his commentary, I think it would be most of the theropod hypothesis, I spent most of the productive to focus my response on the intel- essay outlining the data in support of the thero- lectual framework of Feduccia’s critique of the pod origin and, most exciting to me, describing theropod origin of birds. Specifi cally, I will ask the new directions in evolutionary ornithological the question, “Is this science?” Or is it merely research that have opened up as a consequence. a form of rhetoric designed support an a priori I concluded that one of the most important fron- belief about evolutionary process and history? tiers in ornithological research in this century will be the establishment of a thorough scientifi c THE INTELLECTUAL STRUCTURE OF understanding of the evolution of avian biology FEDUCCIA’S CRITIQUE in light of the theropod origin of birds. From nesting biology and physiology to behavior and A critical element of science is falsifi ability. locomotion, the rewards of studying ornithol- To be scientifi c, a hypothesis must be falsifi able ogy as extant dinosaur biology are only just and yield predictions that are objectively test- beginning to be reaped (Prum 2002). able. In a historical science like evolutionary In his critique of my essay, A. Feduccia (2002) biology, such tests cannot be conducted experi- reviewed much of his previous work but also mentally. However, we can analyze available sprang a new, surprise ending. In summary, evidence with objective repeatable methods. he hypothesized that birds evolved from an Another critical feature of science is the pro- unknown lineage of early basal archosaurs, and posal of alternative hypotheses or theories that that rampant convergent evolution renders the attempt to explain the scientifi c data at hand. many derived morphological characters shared Does Feduccia’s critique meet these minimal by birds and theropods unreliable. However, criteria of science? Feduccia can no longer deny the conclusive evi- Feduccia (2002) offers an alternative to the the- dence that basal dromaeosaurs had feathers (Xu ropod hypothesis of bird origins that is so vague et al. 1999, 2000, 2001, 2003; Czerkas et al. 2002; as to be literally untestable. When Heilmann Norell et al. 2002). In the end, he concedes that (1926) fi rst proposed the basal archosaur hypoth- dromaeosaurs had feathers. In a rhetorical tour esis of avian origins, he described it optimistical- de force that confl icts with decades of his own ly as “wholly without short comings.” Similarly, work and most of his commentary, Feduccia Feduccia (2002) describes his hypothesized early (2002) then hypothesizes that dromaeosaurs ancestral archosaurian lineage as having “less are birds, but that the birds, now including specialized anatomical baggage” than theropod the dromaeosaurs, still originated from some dinosaurs. This ancestral tabula rasa hypothesis has survived the intervening 75 years between them only because it is permanently immune 1 E-mail: [email protected] to falsifi cation. Any potential character confl icts 550 April 2003] Commentary 551 between birds and any known archosaurs can be to avoid dealing with the overwhelming volume rejected as irrelevant because the specifi c organ- of character evidence from all parts of the body isms can be claimend to not actually represent supporting the theropod origin. He frequently the yet unknown, hypothetical ancestor that argues both sides of the same issue wherever perfectly conforms to the theory. Feduccia’s ad- it is convenient. For example, when the fi rst vocacy of an unfalsifi able alternative hypothesis nonavian theropod furcula was described for violates a fundamental tenet of science, but it Velociraptor (Norell et al. 1998), Feduccia and also permits him to continue his permanent rhe- Martin (1998) claimed that the presence of a fur- torical battle against the theropod hypothesis of cula in the basal archosauromorph Longisquama avian origin. demonstrates that those structures have evolved In response to my request for an explicit al- multiple times in archosaurs and are “weak ternative hypothesis of avian origin, Feduccia evidence” of phylogenetic relationship. Now, (2002) concluded that “there are times when applying his “character by character” approach there is insuffi cient evidence to make the for- in this commentary, Feduccia mentions that the mulation of a hypothesis feasible.” Here, he is furcula of Longisquama in an effort to support the not actually engaged in the search for a scien- hypothesis that Longisquama is closely related to tifi c solution to the question of avian origins. birds, in direct contradiction to his earlier pub- Essentially, Feduccia concedes that he would lished conclusions. Simultaneously, he ignores rather not do science (i.e. formulate and test the discoveries since 1998 of furculae or paired alternative hypotheses with data) than to accept clavicles in six to nine major lineages of theropod the theropod origin of birds. Unfortunately, dinosaurs, including dromaeosaurs, ovirap- Feduccia’s rejection of the theropod hypothesis tors, tyrannosaurs, allosaurs, and coelophysids and advocacy of an untestable alternative does (Tykoski et al. 2002). Of course, the only scientifi c not constitute a scientifi c explanation of the ori- way to resolve alternative hypotheses of charac- gin of birds. ter evolution and character confl icts are by ap- Feduccia (2002) also claims that “phylogenet- plying a repeatable, explicit, analytical method ic systematics stands alone among the sciences” to reconstruct evolutionary history of characters in demanding that critics propose a testable and organisms. But Feduccia (2002) openly re- alternative hypothesis. But, as Thomas Kuhn jects available systematics methods as forcing (1970:77) wrote, “The decision to reject one “into algorithmic form what is arguably the most paradigm is always simultaneously the decision subjective and qualitative fi eld of biology.” to accept another, and the judgment leading to Feduccia’s (2002) dogmatic belief in ram- that decision involves the comparison of both pant evolutionary convergence in morphology paradigms with nature and with each other.” literally begs the question—that is, presumes What Feduccia rejects as the irrational demands exactly the facts that need to be demonstrated. of phylogenetic zealots are actually the baseline The only way to demonstrate convergence is to requirements of all sciences, from astrophysics show that the majority of character evidence to zoology. supports a hypothesis of phylogeny in which Because Feduccia’s scenario is untestably the convergent characters are shown to have vague, he is reduced exclusively to criticizing the evolved independently (Patterson 1982, Pinna theropod hypothesis. Feduccia (2002) portrayed 1991). Yet, Feduccia rejects both repeatable the theropod origin of birds as a vast cladisitic systematic methods and explicit, testable al- conspiracy to deceive the ornithological com- ternative hypotheses, making it impossible for munity. Like a conspiracy theorist, he unerringly him to demonstrate the convergence in which interprets evidence—even the new, ultimate he believes. Feduccia (1999a,b; 2002) repeatedly evidence of feathered theropods—as favoring cited his favorite examples of failed phyloge- his preconceived conclusions. Feduccia (2002) netic hypotheses as a justifi cation for rejecting argues that hypotheses of character homology repeatable scientifi c methods, but he failed to cannot be tested by congruence with other char- mention that it was subsequent phylogenetic acters, advocating a character by character ap- analyses that established the preferred hypoth- proach instead. This ad hoc method permits him eses. Actually, the repeatable scientifi c methods to interpret each separate character in whatever that Feduccia rejects are the solution, not the manner he prefers to support his argument, and problem. Feduccia (2002) further states that 552 Commentary [Auk, Vol. 120 the theropod hypothesis implies that drom- tion of the temporal paradox by two thirds (Xu aeosaurs are “avian ancestors,” and that bird et al. 1999, 2000, 2001, 2003; Czerkas et al. 2002; are “derived from dromaeosaurs,” when it is Norell et al. 2002), bird-like nesting behavior in well known that the hypothesis states that the theropods (reviewed in Prum 2002), and most birds and dromaeosaurs (probably including recently by four winged dromaeosaurs (Xu et al. troodontids) are sister groups. 2003). Given that the theropod origin of birds is Feduccia has long maintained that the 80 Ma entirely consistent with and supported by all of “temporal paradox”—the temporal gap in fos- the new evidence discovered in the last decade, sil record between the earliest bird fossils and and that many testable predictions generated the earliest fossils of the proposed avian sister by the hypothesis have been independently taxon (dromaeosaurs and troodontids)—was a supported, it is an overwhelmingly
Load more

Recommended publications
  • Onetouch 4.0 Scanned Documents
    / Chapter 2 THE FOSSIL RECORD OF BIRDS Storrs L. Olson Department of Vertebrate Zoology National Museum of Natural History Smithsonian Institution Washington, DC. I. Introduction 80 II. Archaeopteryx 85 III. Early Cretaceous Birds 87 IV. Hesperornithiformes 89 V. Ichthyornithiformes 91 VI. Other Mesozojc Birds 92 VII. Paleognathous Birds 96 A. The Problem of the Origins of Paleognathous Birds 96 B. The Fossil Record of Paleognathous Birds 104 VIII. The "Basal" Land Bird Assemblage 107 A. Opisthocomidae 109 B. Musophagidae 109 C. Cuculidae HO D. Falconidae HI E. Sagittariidae 112 F. Accipitridae 112 G. Pandionidae 114 H. Galliformes 114 1. Family Incertae Sedis Turnicidae 119 J. Columbiformes 119 K. Psittaciforines 120 L. Family Incertae Sedis Zygodactylidae 121 IX. The "Higher" Land Bird Assemblage 122 A. Coliiformes 124 B. Coraciiformes (Including Trogonidae and Galbulae) 124 C. Strigiformes 129 D. Caprimulgiformes 132 E. Apodiformes 134 F. Family Incertae Sedis Trochilidae 135 G. Order Incertae Sedis Bucerotiformes (Including Upupae) 136 H. Piciformes 138 I. Passeriformes 139 X. The Water Bird Assemblage 141 A. Gruiformes 142 B. Family Incertae Sedis Ardeidae 165 79 Avian Biology, Vol. Vlll ISBN 0-12-249408-3 80 STORES L. OLSON C. Family Incertae Sedis Podicipedidae 168 D. Charadriiformes 169 E. Anseriformes 186 F. Ciconiiformes 188 G. Pelecaniformes 192 H. Procellariiformes 208 I. Gaviiformes 212 J. Sphenisciformes 217 XI. Conclusion 217 References 218 I. Introduction Avian paleontology has long been a poor stepsister to its mammalian counterpart, a fact that may be attributed in some measure to an insufRcien- cy of qualified workers and to the absence in birds of heterodont teeth, on which the greater proportion of the fossil record of mammals is founded.
    [Show full text]
  • ORIGIN and EVOLUTION of BIRDS Dr. Ramesh Pathak B.Sc. (Hons.) –II
    ORIGIN AND EVOLUTION OF BIRDS Dr. Ramesh Pathak B.Sc. (hons.) –II Prof. Parker has shown a number of peculiarities between birds and repiles,so,he said “birds are transformed and glorified reptiles”. Huxley has established a very close relationship by saying birds are “feathered reptiles”. THEORIES OF ORIGIN OF BIRDS A. Cursorial theory : This theory was championed by Baron Nopsa who maintained that the birds evolved from cursorial bipedal dinosaurs. In attempt to move faster during running to pull themselves a bit faster they moved and beat their arms. In such condition, due to continuous use of arms as propellers brought constant increase in the length and breadth of scales present on them. As the scales lengthened ,the pressure against the air caused their edges frayed leading to scales changing into feathers. But this theory was rejected because scales and feathers are fundamentally different structures arising from different layers of skin. B.Tetrapteryx theory :It was proposed by Beebe and Gregorg. According to this theory the ancestors of birds were arboreal reptiles who used to jump from branch to branch and in doing so the scales were transformed into feathers by fraying of the edges. After developing feathers on all the four limbs (Tetrapteryx stage), they used only the anterior wings and the unused posterior wings were lost. This theory was also discarded because there is no evidence that birds had ever four wings. C. Gliding thery : It is based on the idea of Beebe and Georg.It was proposed by Heilmann but does not recognize the tetrapteryx stage.
    [Show full text]
  • Print BB May 2005
    Weather and bird migration Norman Elkins Richard Johnson ABSTRACT Bird migration in and through Britain and Ireland shows great variation, both seasonally and annually. Much depends on atmospheric conditions, which can equally hinder and assist migration, both on a broad scale (the distribution, extent, intensity and movement of pressure patterns), and at a local level (temporal and spatial changes in wind, visibility, cloud and precipitation).All the parameters of bird migration, including timing, routes, speed and duration of migration, are affected, and modified, by a number of meteorological factors, probably the most influential being wind speed and direction.This paper reviews the influence that weather has on bird migration in Britain and Ireland, and discusses examples of the major types of migration. A number of unusual or exceptional migration events are discussed and illustrated with appropriate weather charts. Introduction long-distance expeditions traversing half the Migration is one topic that never fails to appeal planet, such as those by Arctic Terns Sterna par- to the whole spectrum of those with an interest adisaea and Barn Swallows Hirundo rustica,to in birds, from the inveterate ‘twitcher’ to the local movements in response to the temporary general public. Bird migration, defined simply freezing of freshwater bodies. Differences in as regular movements from one area to another, migration strategy and behaviour result in generally occurs in response to the availability some species undertaking nocturnal migration, of food resources and encompasses an enor- while others move mainly during daylight mous variety of methods. These range from hours. These differences operate not only 238 © British Birds 98 • May 2005 • 238-256 126.
    [Show full text]
  • Paravian Phylogeny and the Dinosaur-Bird Transition: an Overview
    feart-06-00252 February 11, 2019 Time: 17:42 # 1 REVIEW published: 12 February 2019 doi: 10.3389/feart.2018.00252 Paravian Phylogeny and the Dinosaur-Bird Transition: An Overview Federico L. Agnolin1,2,3*, Matias J. Motta1,3, Federico Brissón Egli1,3, Gastón Lo Coco1,3 and Fernando E. Novas1,3 1 Laboratorio de Anatomía Comparada y Evolución de los Vertebrados, Museo Argentino de Ciencias Naturales Bernardino Rivadavia, Buenos Aires, Argentina, 2 Fundación de Historia Natural Félix de Azara, Universidad Maimónides, Buenos Aires, Argentina, 3 Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires, Argentina Recent years witnessed the discovery of a great diversity of early birds as well as closely related non-avian theropods, which modified previous conceptions about the origin of birds and their flight. We here present a review of the taxonomic composition and main anatomical characteristics of those theropod families closely related with early birds, with the aim of analyzing and discussing the main competing hypotheses pertaining to avian origins. We reject the postulated troodontid affinities of anchiornithines, and the Edited by: dromaeosaurid affinities of microraptorians and unenlagiids, and instead place these Corwin Sullivan, University of Alberta, Canada groups as successive sister taxa to Avialae. Aiming to evaluate previous phylogenetic Reviewed by: analyses, we recoded unenlagiids in the traditional TWiG data matrix, which resulted Thomas Alexander Dececchi, in a large polytomy at the base of Pennaraptora. This indicates that the TWiG University of Pittsburgh, United States phylogenetic scheme needs a deep revision. Regarding character evolution, we found Spencer G. Lucas, New Mexico Museum of Natural that: (1) the presence of an ossified sternum goes hand in hand with that of ossified History & Science, United States uncinate processes; (2) the presence of foldable forelimbs in basal archosaurs indicates *Correspondence: widespread distribution of this trait among reptiles, contradicting previous proposals Federico L.
    [Show full text]
  • The Origin of Birds
    The Origin of Birds Birds have many unusual synapomorphies among modern animals: [ Synapomorphies (shared derived characters), representing new specializations evolved in the most recent common ancestor of the ingroup] • Feathers • Warm-blooded (also in mammals) • Specialized lungs & air-sacs • Hollow bones • Toothless beaks • Large brain Technical name for birds is Aves, and “avian” means “of or concerning birds”. • Cervicals very different from dorsals, allowing neck to fold into “S”-shape • Backwards-pointing pubis • Synsacrum (sacrum fused to pelves; pelvic bones • Fibula reduced to proximal splint fused together) • Astragalus & calcaneum fused to tibia • Proximal caudals very mobile • Hinge-like ankle joint • Pygostyle (distal caudals all fused together) • Furcula - (the wishbone) • Tarsometatarsus (distal tarsals fused to • Forelimb very long, has become wing metatarsals; all metatarsals fused together) • Carpometacarpus (semilunate carpal block fused • Main pedal digits II-IV to metacarpals; all metacarpals fused together) • Pedal digit I reversed, placed at bottom of • Three fingers, but digits all reduced so no unguals tarsometatarsus 1 Compare modern birds to their closest relatives, crocodilians • Difficult to find relatives using only modern animals (turtles have modified necks and toothless beaks, but otherwise very • different; bats fly and are warm-blooded, but are clearly mammals; etc.) • With discovery of fossils, other potential relations: pterosaurs had big brains, “S”- shaped neck, hinge-like foot, but wings are VERY different. • In 1859, Darwin published the Origin; some used birds as a counter-example against evolution, as there were apparently known transitional forms between birds and other vertebrates. In 1860, a feather (identical to modern birds' feathers) was found in the Solnhofen Lithographic Limestone of Bavaria, Germany: a Late Jurassic formation.
    [Show full text]
  • On the Origin and Evolution of Nest Building by Passerine Birds’
    T H E C 0 N D 0 R r : : ,‘ “; i‘ . .. \ :i A JOURNAL OF AVIAN BIOLOGY ,I : Volume 99 Number 2 ’ I _ pg$$ij ,- The Condor 99~253-270 D The Cooper Ornithological Society 1997 ON THE ORIGIN AND EVOLUTION OF NEST BUILDING BY PASSERINE BIRDS’ NICHOLAS E. COLLIAS Departmentof Biology, Universityof California, Los Angeles, CA 90024-1606 Abstract. The object of this review is to relate nest-buildingbehavior to the origin and early evolution of passerinebirds (Order Passeriformes).I present evidence for the hypoth- esis that the combinationof small body size and the ability to place a constructednest where the bird chooses,helped make possiblea vast amountof adaptiveradiation. A great diversity of potential habitats especially accessibleto small birds was created in the late Tertiary by global climatic changes and by the continuing great evolutionary expansion of flowering plants and insects.Cavity or hole nests(in ground or tree), open-cupnests (outside of holes), and domed nests (with a constructedroof) were all present very early in evolution of the Passeriformes,as indicated by the presenceof all three of these basic nest types among the most primitive families of living passerinebirds. Secondary specializationsof these basic nest types are illustratedin the largest and most successfulfamilies of suboscinebirds. Nest site and nest form and structureoften help characterizethe genus, as is exemplified in the suboscinesby the ovenbirds(Furnariidae), a large family that builds among the most diverse nests of any family of birds. The domed nest is much more common among passerinesthan in non-passerines,and it is especially frequent among the very smallestpasserine birds the world over.
    [Show full text]
  • Testing the Neoflightless Hypothesis: Propatagium Reveals Flying Ancestry
    J Ornithol DOI 10.1007/s10336-015-1190-9 ORIGINAL ARTICLE Testing the neoflightless hypothesis: propatagium reveals flying ancestry of oviraptorosaurs 1 2 Alan Feduccia • Stephen A. Czerkas Received: 4 September 2014 / Revised: 31 December 2014 / Accepted: 23 February 2015 Ó Dt. Ornithologen-Gesellschaft e.V. 2015 Abstract Considerable debate surrounds the numerous Zusammenfassung avian-like traits in core maniraptorans (ovirap- torosaurs, troodontids, and dromaeosaurs), especially in the Die ,,Neoflightless‘‘-Hypothese im Test: Halsflughaut Chinese Early Cretaceous oviraptorosaur Caudipteryx, (Propatagium) offenbart flugfa¨hige Vorfahren der which preserves modern avian pennaceous primary remi- Oviraptorosauria ges attached to the manus, as is the case in modern birds. Was Caudipteryx derived from earth-bound theropod di- Es gibt eine ausgiebige Debatte u¨ber die zahlreichen vo- nosaurs, which is the predominant view among palaeon- gela¨hnlichen Eigenheiten der Maniraptora (Oviraptosaurus, tologists, or was it secondarily flightless, with volant avians Troodontidae, Dromaeosaurus), vor allem des (gefiederten) or theropods as ancestors (the neoflightless hypothesis), Oviraptorosauria Caudipteryx aus der fru¨hen chinesischen which is another popular, but minority view. The discovery Kreidezeit, der genau wie rezente Vo¨gel Handschwingen here of an aerodynamic propatagium in several specimens hatte, die an den Handknochen ansetzen. Stammt Cau- provides new evidence that Caudipteryx (and hence ovi- dipteryx von den nur am Erdboden lebenden Theropoda ab - raptorosaurs) represent secondarily derived flightless die unter den Pala¨ontologen vorherrschende Meinung -, oder ground dwellers, whether of theropod or avian affinity, and war er sekunda¨r flugunfa¨hig und stammte von flugfa¨higen that their presence and radiation during the Cretaceous may Theropoden ab - die ,,Neoflightless‘‘-Hypothese, eine alter- have been a factor in the apparent scarcity of many other native, wenn auch nur von Wenigen unterstu¨tzte These.
    [Show full text]
  • Interpreting Behavior from Early Cretaceous Bird Tracks and the Morphology of Bird Feet and Trackways
    INTERPRETING BEHAVIOR FROM EARLY CRETACEOUS BIRD TRACKS AND THE MORPHOLOGY OF BIRD FEET AND TRACKWAYS By ©2009 Amanda Renee Falk B.S., Lake Superior State University, 2007 Submitted to the Department of Geology and the Faculty of the Graduate School of the University of Kansas In partial fulfillment of the requirements for the degree of Master of Science Advisory Committee: ______________________________ Co-Chairman: Stephen T. Hasiotis ______________________________ Co-Chairman: Larry D. Martin ______________________________ J. F. Devlin Date Defended: September 15th, 2009 The thesis committee for Amanda R. Falk certifies that this is the approved version of the following thesis: INTERPRETING BEHAVIOR FROM EARLY CRETACEOUS BIRD TRACKS AND THE MORPHOLOGY OF BIRD FEET AND TRACKWAYS Advisory Committee: ____________________________ Stephen T. Hasiotis, Chairman ____________________________ Larry D. Martin, Co-Chairman ____________________________ J. F. Devlin Date approved: _ September 15th, 2009_ ii ABSTRACT Amanda R. Falk Department of Geology, September 2009 University of Kansas Bird tracks were studied from the Lower Cretaceous Lakota Formation in South Dakota, USA, and the Lower Cretaceous Haman Formation, South Korea. Behaviors documented from the Lakota Formation included: (1) a takeoff behavior represented by a trackway terminating in two subparallel tracks; (2) circular walking; and (3) the courtship display high stepping. Behaviors documented from the Haman Formation included: (1) a low-angle landing in which the hallux toe was dragged; (2) pecking and probing behaviors; and (3) flapping-assisted hopping during walking. The invertebrate trace fossil Cochlichnus was associated the avian tracks from the Lakota Formation. No traces of pecking or probing were associated with Cochlichnus. The invertebrate trace fossils Cochlichnus, Arenicholites, and Steinichnus were found associated the bird tracks from the Haman Formation.
    [Show full text]
  • The Origin and Diversification of Birds
    Current Biology Review The Origin and Diversification of Birds Stephen L. Brusatte1,*, Jingmai K. O’Connor2,*, and Erich D. Jarvis3,4,* 1School of GeoSciences, University of Edinburgh, Grant Institute, King’s Buildings, James Hutton Road, Edinburgh EH9 3FE, UK 2Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China 3Department of Neurobiology, Duke University Medical Center, Durham, NC 27710, USA 4Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA *Correspondence: [email protected] (S.L.B.), [email protected] (J.K.O.), [email protected] (E.D.J.) http://dx.doi.org/10.1016/j.cub.2015.08.003 Birds are one of the most recognizable and diverse groups of modern vertebrates. Over the past two de- cades, a wealth of new fossil discoveries and phylogenetic and macroevolutionary studies has transformed our understanding of how birds originated and became so successful. Birds evolved from theropod dino- saurs during the Jurassic (around 165–150 million years ago) and their classic small, lightweight, feathered, and winged body plan was pieced together gradually over tens of millions of years of evolution rather than in one burst of innovation. Early birds diversified throughout the Jurassic and Cretaceous, becoming capable fliers with supercharged growth rates, but were decimated at the end-Cretaceous extinction alongside their close dinosaurian relatives. After the mass extinction, modern birds (members of the avian crown group) explosively diversified, culminating in more than 10,000 species distributed worldwide today. Introduction dinosaurs Dromaeosaurus albertensis or Troodon formosus.This Birds are one of the most conspicuous groups of animals in the clade includes all living birds and extinct taxa, such as Archaeop- modern world.
    [Show full text]
  • Body and Limb Size Dissociation at the Origin of Birds: Uncoupling Allometric Constraints Across a Macroevolutionary Transition
    ORIGINAL ARTICLE doi:10.1111/evo.12150 BODY AND LIMB SIZE DISSOCIATION AT THE ORIGIN OF BIRDS: UNCOUPLING ALLOMETRIC CONSTRAINTS ACROSS A MACROEVOLUTIONARY TRANSITION T. Alexander Dececchi1,2 and Hans C. E. Larsson3 1Biology Department, University of South Dakota, 414 E Clark Street, Vermillion, South Dakota 57069 2E-mail: [email protected] 3Redpath Museum, McGill University, 859 Sherbrooke Street West, Montreal, Quebec H3A 2K6 089457 Received May 30, 2012 Accepted April 17, 2013 The origin of birds and powered flight is a classic major evolutionary transition. Research on their origin often focuses on the evolution of the wing with trends of forelimb elongation traced back through many nonavian maniraptoran dinosaurs. We present evidence that the relative forelimb elongation within avian antecedents is primarily due to allometry and is instead driven by a reduction in body size. Once body size is factored out, there is no trend of increasing forelimb length until the origin of birds. We report that early birds and nonavian theropods have significantly different scaling relationships within the forelimb and hindlimb skeleton. Ancestral forelimb and hindlimb allometric scaling to body size is rapidly decoupled at the origin of birds, when wings significantly elongate, by evolving a positive allometric relationship with body size from an ancestrally negative allometric pattern and legs significantly shorten by keeping a similar, near isometric relationship but with a reduced intercept. These results have implications for the evolution of powered flight and early diversification of birds. They suggest that their limb lengths first had to be dissociated from general body size scaling before expanding to the wide range of fore and hindlimb shapes and sizes present in today’s birds.
    [Show full text]
  • [Chime Plays] [Music Plays] [CLARKE (Narration):] the Animal Kingdom Is
    [chime plays] [music plays] [CLARKE (narration):] The animal kingdom is made up of major groups, recognized by key traits. Fish have fins. Some land animals have four legs, others six, and several different groups have wings. Biologists have long sought to discover how groups of animals, and their key features, evolved. And one of the greatest mysteries has been the origin of birds. Our world has more than 10,000 species of birds with feathered wings. Where did birds come from, and how did wings and feathers first arise? To find out, scientists have scoured the fossil record. … And they have uncovered surprising twists in the evolution of birds from their flightless ancestors. [CLARKE (to camera):] In the past 30 years we’ve found a treasure trove of new fossil discoveries. They’ve made the origin of birds one of the best-documented transitions in the history of life. [music plays] [birds call] [CLARKE (narration):] I am fascinated by birds. And as a paleontologist, I’ve spent my career chasing their evolutionary origins in the fossil record. [CLARKE (to camera):] Above all else, what makes birds unique are their wings. They’re made of feathers that are stiff yet flexible. And bird wings are even more remarkable than airplane wings, because they can flap, which allows them to maneuver rapidly and ultimately defy gravity. [CLARKE (narration):] The quest to understand the origin of birds and other animals began in earnest over 150 years ago. When Charles Darwin wrote “The Origin of Species,” he argued that every major group of animals evolved from a pre-existing one.
    [Show full text]
  • Origins of Avian Flight – a New Perspective
    Origins of avian flight – a new perspective Larry D. Martin Department of Ecology and Evolutionary Biology; Museum of Natural History and Biodiversity Research Center, University of Kansas, Lawrence, KS 66045, USA e-mail: [email protected] ABSTRACT - The discovery of a primitive bird-like dromaeosaur (Microraptor) with four functional wings vindicates Beebe’s suggestion that birds went through a tetrapteryx stage in the origin of flight. Flight originated from an arboreal glid- ing ancestor and Longisquama may be more central to understanding how this came about than previously supposed. Keywords: Dromaeosaur, Microraptor, Longisquama, birds, flight, Upper Triassic, Lower Cretaceous Les origines du vol avien – Perspectives nouvelles - La découverte d’un dromaeosaure semblable à un oiseau primitif (Microraptor) avec quatre ailes fonctionnelles justifie la suggestion de Beebe selon laquelle les oiseaux sont passés par un stade tetrapteryx dans l’origine du vol. Le vol est apparu chez un ancêtre arboricole planeur, et Longisquama est peut être plus important qu’on l’a supposé pour comprendre les modalités de cette transition. INTRODUCTION the stratigraphically older Deinonychus studied by Ostrom (1969). In this sense the fossil record did not provide an Much of the argument over flight origins revolves orderly progression from terrestrial “maniraptorians” to fly- around Archaeopteryx, the first bird to be recognized from ing birds. In fact, Archaeopteryx, a very typical bird in most the Mesozoic and still the oldest known bird. Archaeop- respects, is significantly older than any credible evidence for teryx displays a remarkable combination of avian and reptil- dromaeosaurs, the dinosaurs thought to be closest to birds. ian characters and has become the archetype of a “missing Functionally there are additional problems.
    [Show full text]