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![Reconstruction of Scansoriopteryx (=Epidendrosaurus), upper left, as a trunk-climbing glider; subsequent study of the specimen using Keyence microscopy showed hind-limb wings, providing new evidence for tetrapteryx gliding (see inset sketch by S. A. Czerkas). Lower, reconstructions of currently known scansoriopterids as terrestrial cursors, a reconstruction that is highly improbable and dictated by attempts to " accommodate the cladograms " indicating direct " dinosaur' descendancy. Their pelves are not adapted for cursorial habits and in Scansoriopteryx the acetabulum is nearly closed, with no supra-acetabular crest. The femur, too, is not that of a bipedal cursor [see 18]. The other genera are quite similar in pelvic anatomy. Upper right, Digital Keyence image of the skull of Scansoriopteryx, similar to oviraptorosaurids, which is not that of a dinosaur, and the teeth are, like those of Epidexipteryx and Yi, simple peg-like teeth constricted at the base, similar to those of oviraptorosaurs and Mesozoic birds. Scansoriopteryx, upper left, reconstruction . . . By Matt Martyniuk, 2011 [CC: (http://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons. Digital Keyence microscopy [see 18] image of skull, counterslab, courtesy Stephen A. and Sylvia J. Czerkas; copyright Stephen A. Czerkas; Institute of Geology, Chinese Academy of Sciences, CAGS02-IG-gausa-1/DM 607. Lower, left to right, reconstructions of Epidendrosaurus (=Scansoriopteryx), Epidexipteryx, and Yi, by Lida Xing, in: Padian, K. [26]; Reprinted by permission from Macmillan Publishers Ltd: Nature. Padian K. Dinosaur up in the air. Nature (News and Views) 2015; doi:10.1038/nature14392 (copyright 2015). Scale bars: skull, 1 cm; lower images, 5 cm.](profile/Alan-Feduccia/publication/301913740/figure/fig1/AS:362578439098368@1463456844793/Fig-1-Reconstruction-of-Scansoriopteryx-Epidendrosaurus-upper-left-as-a.png)
Reconstruction of Scansoriopteryx (=Epidendrosaurus), upper left, as a trunk-climbing glider; subsequent study of the specimen using Keyence microscopy showed hind-limb wings, providing new evidence for tetrapteryx gliding (see inset sketch by S. A. Czerkas). Lower, reconstructions of currently known scansoriopterids as terrestrial cursors, a reconstruction that is highly improbable and dictated by attempts to " accommodate the cladograms " indicating direct " dinosaur' descendancy. Their pelves are not adapted for cursorial habits and in Scansoriopteryx the acetabulum is nearly closed, with no supra-acetabular crest. The femur, too, is not that of a bipedal cursor [see 18]. The other genera are quite similar in pelvic anatomy. Upper right, Digital Keyence image of the skull of Scansoriopteryx, similar to oviraptorosaurids, which is not that of a dinosaur, and the teeth are, like those of Epidexipteryx and Yi, simple peg-like teeth constricted at the base, similar to those of oviraptorosaurs and Mesozoic birds. Scansoriopteryx, upper left, reconstruction . . . By Matt Martyniuk, 2011 [CC: (http://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons. Digital Keyence microscopy [see 18] image of skull, counterslab, courtesy Stephen A. and Sylvia J. Czerkas; copyright Stephen A. Czerkas; Institute of Geology, Chinese Academy of Sciences, CAGS02-IG-gausa-1/DM 607. Lower, left to right, reconstructions of Epidendrosaurus (=Scansoriopteryx), Epidexipteryx, and Yi, by Lida Xing, in: Padian, K. [26]; Reprinted by permission from Macmillan Publishers Ltd: Nature. Padian K. Dinosaur up in the air. Nature (News and Views) 2015; doi:10.1038/nature14392 (copyright 2015). Scale bars: skull, 1 cm; lower images, 5 cm.
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Adherents of the current orthodoxy of a derivation of birds from theropod dinosaurs, criticize the commentary by Feduccia (2013, Auk, 130) [1 - 12] entitled "Bird Origins Anew" as well as numerous papers by Lingham-Soliar on theropod dermal fibers, using numerous mischaracterizations and misstatements of content, and illustrate their own misconcept...
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... This was summarized by Feduccia (2012, p. 23) as "an earlier origin of birds from a common basal archosaur or dinosauromorph stem-ancestor of theropods and birds" (cf. Czerkas et al. 2002;Martin 2004Martin , 2008Feduccia et al. 2005;Feduccia 2012Feduccia , 2013Feduccia , 2016Feduccia , 2020Czerkas and Feduccia 2014;Feduccia and Czerkas 2015). It has been modified to incorporate the auxiliary hypothesis that at least the pennaraptoran maniraptorans (Oviraptorosauria, Troodontidae, and Dromaeosauridae, i.e., those maniraptorans with unambiguously pennaceous feathers) are birds at all stages of flight and flight loss rather than theropod dinosaurs (thus differing fundamentally from the otherwise similar hypothesis of Paul 2002); similarities with theropods are explained as homoplasy channeled by shared stem ancestry and, in the case of flight loss, by neotenic retention of plesiomorphic archosaurian character states and character reversal associated with 3 It also implies that critics of BADM deny that birds and dinosaurs are closely related, but this is false. ...
... Protagonists on all sides of the debate concur that birds are nested within Archosauria, closely allied with dinosaurs." reacquisition of a terrestrial mode of life (e.g., as in "ratites") (for reviews see James and Pourtless 2009;Feduccia 2012Feduccia , 2013Feduccia , 2016Feduccia , 2020. Perhaps because of the simplifying tendency mentioned, Havstad and Smith do not appreciate the significance of this auxiliary hypothesis: it is dismissed (pp. ...
... It will be objected that the non-rational factors enumerated above are only partially explanatory of the success of BADM: the empirical record anchors the characterization of BADM as a "progressive research program." With two exceptions-digital homology (for reviews see: James and Pourtless 2009;Xu et al. 2009;Larsson et al. 2010;Makovicky and Zanno 2011;Young et al. 2011;Feduccia 2012Feduccia , 2016Feduccia , 2020Xu and Mackem 2013;Salinas-Saavedra et al. 2014;Guinard 2016) and the mode in which avian flight originated-Havstad and Smith simply assume that all the purported "corroborations" of BADM are empirically sound (p. 843ff and their Fig. 2). ...
Havstad and Smith (2019) argue that Lakatos’ “methodology of scientific research programs” (MSRP) is a promising philosophical framework for explaining the perceived empirical success of the hypothesis that birds are maniraptoran theropod dinosaurs, and the perceived empirical failures or stagnation of alternatives to that hypothesis. These conclusions are rejected: Havstad and Smith’s account of the alternative “research programs” inadequately characterizes criticism of the hypothesis that birds are maniraptoran theropods and they neither offer sufficient modifications to MSRP to correct its known difficulties in deriving logically or empirically satisfactory criteria for the assessment and preferential selection of “research programs” from historiographical data, nor proposals to mitigate its tendency to promote confirmation bias and dogmatism. Independent flight loss, an important problem in systematic ornithology with implications for the origin of birds, provides a supplementary demonstration of how the application of MSRP in the present context would tend systematically to mislead investigations of the evolutionary history of birds by promoting an uncritical perspective. Given these difficulties, MSRP is an unacceptable philosophical framework for evaluating alternative hypotheses for the origin of birds.
... As formas basais, como Epidendrosaurus, apresentariam indícios de rêmiges em seus membros posteriores, e uma pélvis não apta para o hábito cursorial bípede. É possível que utilizasse ambos os membros anteriores e posteriores durante a escalada (Feduccia, 2016). ...
Muitas adaptações são necessárias para que um animal cursorial terrestre desenvolva capacidade voadora plena. A capacidade de planar, mesmo sendo energeticamente mais simples, ainda exige uma série de adaptações morfológicas no sentido de desenvolver estruturas geradoras de sustentação e modificações no plano corporal do animal. O presente trabalho explora as características aerodinâmicas e biomecânicas de quatro morfótipos maniraptoriformes com prováveis capacidades planadoras: Microraptor, Yi, Ambopteryx e Archaeopteryx. O objetivo é levantar novos parâmetros para o entendimento da origem do voo em avianos. Para isto utilizam-se de modelos virtuais, criados a partir dos respectivos fósseis, e reconstruções propostas pela literatura, além de novas interpretações aqui discutidas. Desta forma se propõe o contexto evolutivo provável em que surgem os aerofólios membranosos em Scansoriopterygidae.
... That same year, the fervor surrounding Ostrom's theropod hypothesis led one commentator to dub it the Birds-Are-Dinosaurs-Movement, or BADM (Olson 2002). Since then, discussion between BADM and its opposition-the notion that Birds-Are-Not-Dinosaurs, or BAND-has turned downright acrimonious (Feduccia 2002(Feduccia , 2013(Feduccia , 2016Prum 2003;Smith et al. 2015). All this despite the fact that, in the time between Ostrom's 1969 discovery of D. antirrhopus and now, many purportedly key pieces of evidence have been discovered (Barsbold 1983;Qiang et al. 1998;Xu et al. 2003;Lipkin et al. 2007;Nesbitt et al. 2009;Xu et al. 2009;Xing et al. 2016;Smithwick et al. 2017;McNamara et al. 2018), several supposedly comprehensive analyses have been conducted (Chiappe 1995;Turner et al. 2012;Clarke 2013;Brusatte et al. 2014), and various pleading appeals to scientific virtue have been made (Feduccia 2002(Feduccia , 2013(Feduccia , 2016Prum 2003;Smith et al. 2015). ...
... Since then, discussion between BADM and its opposition-the notion that Birds-Are-Not-Dinosaurs, or BAND-has turned downright acrimonious (Feduccia 2002(Feduccia , 2013(Feduccia , 2016Prum 2003;Smith et al. 2015). All this despite the fact that, in the time between Ostrom's 1969 discovery of D. antirrhopus and now, many purportedly key pieces of evidence have been discovered (Barsbold 1983;Qiang et al. 1998;Xu et al. 2003;Lipkin et al. 2007;Nesbitt et al. 2009;Xu et al. 2009;Xing et al. 2016;Smithwick et al. 2017;McNamara et al. 2018), several supposedly comprehensive analyses have been conducted (Chiappe 1995;Turner et al. 2012;Clarke 2013;Brusatte et al. 2014), and various pleading appeals to scientific virtue have been made (Feduccia 2002(Feduccia , 2013(Feduccia , 2016Prum 2003;Smith et al. 2015). The dispute has lingered, while the discussion has soured. ...
... Given the preexisting need for a new and more exacting framework, and while recalling the remarkably antagonistic character of the recent debate between BADM and BAND, neither is it hard to understand how plausible objections to contentious scientific practice might have been mistakenly expressed as accusations of nonscientific practice (Prum 2003); nor is it hard to imagine why such accusations might have unproductively escalated rather than advanced the debate (Feduccia 2013(Feduccia , 2016Smith et al. 2015). No well-trained scientist engaged in good-faith scientific research at a recognizably scientific institution wants to be accused of doing nonscientific work by other scientists merely because they are engaged in a longrunning scientific disagreement (Ostrom 1969;Gauthier 1986;Smith et al. 2015;Feduccia 2016). ...
The last half century of paleornithological research has transformed the way that biologists perceive the evolutionary history of birds. This transformation has been driven, since 1969, by a series of exciting fossil discoveries combined with intense scientific debate over how best to interpret these discoveries. Ideally, as evidence accrues and results accumulate, interpretive scientific agreement forms. But this has not entirely happened in the debate over avian origins: the accumulation of scientific evidence and analyses has had some effect, but not a conclusive one, in terms of resolving the question of avian origins. Although the majority of biologists have come to accept that birds are dinosaurs, there is lingering and, in some quarters, strident opposition to this view. In order to both understand the ongoing disagreement about avian origins and generate a prediction about the future of the debate, here we use a revised model of scientific practice to assess the current and historical state of play surrounding the topic of bird evolutionary origins. Many scientists are familiar with the metascientific scholars Sir Karl Popper and Thomas Kuhn, and these are the primary figures that have been appealed to so far, in prior attempts to assess the dispute. But we demonstrate that a variation of Imre Lakatos’s model of progressive versus degenerative research programmes provides a novel and productive assessment of the debate. We establish that a refurbished Lakatosian account both explains the intractability of the dispute and predicts a likely outcome for the debate about avian origins. In short, here, we offer a metascientific tool for rationally assessing competing theories—one that allows researchers involved in seemingly intractable scientific disputes to advance their debates.
... Atualmente a origem das aves deixou de ser um mistério, sendo consolidado com base nos diversos dados que a ciência obteve em relação a este grupo ter sido originado a partir de dinossauros terópodes (Chiappe, & Witmer, 2002;Figueiredo & Cardoso, 2010;Favretto, 2010). Apesar dessa definição, alguns pesquisadores ainda discordam da origem terópoda das aves, focando mais em aspectos anatômicos e da origem das penas (Feduccia, 2016). No entanto, menos conhecida do que esta controvérsia, está a proposta por Ellenberger (1977) (Ellenberger, 1977), cuja hipótese associa a origem das aves ao prolacertideo Cosesaurus. ...
Apesar de hoje já consolidada a origem das aves a partir de Theropoda, durante os anos de 2007 a 2010, o pesquisador Maurice Pomarède tentou refutar a origem das aves a partir de dinossauros terópodes, principalmente por meio do fóssil de Cosesaurus aviceps (Prolacerta). Também tentou identificar diversos pontos para tentar refutar essa origem aviana, com afirmações de que o peso seria inimigo do voo, que o voo não poderia ter se originado do solo e que escamas de dinossauros não poderiam originar penas. No presente trabalho todos estes argumentos são analisados de forma a demonstrar como a origem Theropoda das aves está atualmente consolidada em bases parcimoniosas.
... For most paleontologists the accepted view is that there was a homeotic shift that occurred somewhere "between Allosaurus and birds" (whatever that means?) resulting in avian manual condensations II-III-IV transforming into digits I-II-III. What could have possibly caused this mysterious and unique transition [16]? ...
... One can now ask if the newly designated Pennaraptora (oviraptorosaurids, troodontids and dromaeosaurids), along with birds, represents a clade distinctive from true theropods, with manual digits II-III-IV [15,16]? If so, the current phylogeny advocated by Chiappe and Meng is topsy-turvy. ...
Birds of Stone contains a portfolio of outstanding photographs of the spectacularly preserved Jehol bird fossils, from the Chinese Lower Cretaceous, and other pertinent vertebrate fossils of varying ages, along with comments on each fossil. The book nicely illustrates a range of species of the radiation of enantiornithines (opposite birds), the dominant Mesozoic landbirds, as well as the ornithuromorphs, the Mesozoic antecedents of the modern neornithine birds. Although the first section of the book is fairly straight forward, the second section, on bird origins and their early evolution is one-sided, presenting only the popular paleontological view and omits discussion of controversial subjects. Examples are the highly speculative presence of dinosaur protofeathers and improbable scenarios of flight origins. There are no citations of the numerous credible opposing views in the literature.
The natural history of birds is summarized. Account of what contemporary birds are, when and how they came to be what they are, and why and how they evolved exceptional physiognomies are given. The evolution of birds from reptilian stock, their domestication that resulted in some of the species becoming leading food animals and the sociocultural impacts of birds on organizations of many human societies are outlined. The evolution of the lung-air sac system of birds, which among the air-breathing vertebrates is the most structurally complex and efficient gas exchanger, is described. Unique properties, capacities, and activities such as long distant migration, flight under the extremely hypoxic conditions of high altitude, anthropogenic impacts of climate change (global warming) on the ecology and biology of birds, sound production (vocalization), birds as bioindicator animals of environmental health, and the cognitive prowess of birds in exploits such as dropping hard food objects on firm surfaces to break them and that way access otherwise unobtainable food and caching of food in various ways and places and shrewdly accessing it for use during adverse conditions are presented. The biology of birds can only be well understood by considering them from various perspectives that include the habitats they occupy and the lifestyles that they lead.
The term "homology" is persistently polysemous, defying the expectation that extensive scientific research should yield semantic stability. A common response has been to seek a unification of various prominent definitions. This paper proposes an alternative strategy, based on the insight that scientific concepts function as tools for research: When analyzing various conceptualizations of homology, we should preserve those distinguishing features that support particular research goals. We illustrate the fruitfulness of our strategy by application to two cases. First, we revisit Lankester's celebrated evolutionary reappraisal of homology and argue that his analysis has been distorted by assimilation to modern agendas. His "homogeny" does not mean the same thing as modern evolutionary "homology," and his "homoplasy" is no mere antonym. Instead, Lankester uses both new terms to pose a question that remains strikingly relevant-how do mechanistic and historical causes of morphological resemblance interact? Second, we examine the puzzle of avian digit homology, which exemplifies disciplinary differences in homology conceptualization and assessment. Recent progress has been fueled by the development of new tools within the relevant disciplines (paleontology and developmental biology) and especially by increasing interdisciplinary cooperation. Conceptual unification has played very little role in this work, which instead seeks concrete evolutionary scenarios that integrate all the available evidence. Together these cases indicate the complex relationship between concepts and other tools in homology research.
Feathers have long been regarded as the innovation that drove the success of birds. However, feathers have been reported from close dinosaurian relatives of birds, and now from ornithischian dinosaurs and pterosaurs, the cousins of dinosaurs. Incomplete preservation makes these reports controversial. If true, these findings shift the origin of feathers back 80 million years before the origin of birds. Gene regulatory networks show the deep homology of scales, feathers, and hairs. Hair and feathers likely evolved in the Early Triassic ancestors of mammals and birds, at a time when synapsids and archosaurs show independent evidence of higher metabolic rates (erect gait and endothermy), as part of a major resetting of terrestrial ecosystems following the devastating end-Permian mass extinction.
Since the 1990s, the avian fossil record has been greatly advanced with the oldest record found from the Upper Jurassic and a pan-global distribution discovered in the Cretaceous. Birds possess highly modified skeletal characteristics such as the pygostyle, keeled sternum, forelimbs developed as wings, and toothless jaws, all of which are considered to have evolved in relation to flight. Recent discoveries have also revealed that Mesozoic birds had made various ecological developments including sexual dimorphism and differential growth rates. Although the reasons for the limited diversification of flightless birds in the Mesozoic and for the survival of the Neornithes through the K-Pg mass extinction event are still not well understood, they may be attributed to environmental and physiological limitations. In this paper, I suggest that the development of flight capability, endothermy, and efficient digestive systems may have been involved in the diversification and wide geographical distribution of birds. Although physiological characteristics are rarely preserved in the fossil record, new fossil discoveries and advancements in research on soft tissue reconstruction might reveal more details of the ecology of extinct birds in the near future.
