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Abstract

Birds evolved from and are phylogenetically recognized as members of the theropod dinosaurs; their first known member is the Late Jurassic Archaeopteryx, now represented by seven skeletons and a feather, and their closest known non-avian relatives are the dromaeosaurid theropods such as Deinonychus. Bird flight is widely thought to have evolved from the trees down, but Archaeopteryx and its outgroups show no obvious arboreal or tree-climbing characters, and its wing planform and wing loading do not resemble those of gliders. The ancestors of birds were bipedal, terrestrial, agile, cursorial and carnivorous or omnivorous. Apart from a perching foot and some skeletal fusions, a great many characters that are usually considered ‘avian’ (e.g. the furcula, the elongated forearm, the laterally flexing wrist and apparently feathers) evolved in non-avian theropods for reasons unrelated to birds or to flight. Soon after Archaeopteryx, avian features such as the pygostyle, fusion of the carpometacarpus, and elongated curved pedal claws with a reversed, fully descended and opposable hallux, indicate improved flying ability and arboreal habits. In the further evolution of birds, characters related to the flight apparatus phylogenetically preceded those related to the rest of the skeleton and skull. Mesozoic birds are more diverse and numerous than thought previously and the most diverse known group of Cretaceous birds, the Enantiornithes, was not even recognized until 1981. The vast majority of Mesozoic bird groups have no Tertiary records: Enantiornithes, Hesperornithiformes, Ichthyornithiformes and several other lineages disappeared by the end of the Cretaceous. By that time, a few Linnean ‘Orders’ of extant birds had appeared, but none of these taxa belongs to extant ‘families’, and it is not until the Paleocene or (in most cases) the Eocene that the majority of extant bird ‘Orders’ are known in the fossil record. There is no evidence for a major or mass extinction of birds at the end of the Cretaceous, nor for a sudden ‘bottleneck’ in diversity that fostered the early Tertiary origination of living bird ‘Orders’.

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... OVER THE LAST 25 years, few topics in systematics and paleontology have been as divisively debated as the origin of birds (Padian and Chiappe 1998;Feduccia 1999a, b;Dalton 2000). For most of the middle of the twentieth century, G. Heilmann's (1926) monumental analysis of the topic reigned unchallenged. ...
... Many dromaeosaurs, ornithomimid, ovi-raptoran, and other theropod fossils included in the hypothesis are best known from the Late Cretaceous, or about 80 Ma, but many are known from much earlier. The notion of a temporal paradox is based on several fundamental misconceptions about paleontology and evolutionary biology (Padian and Chiappe 1998), and by misrepresentation of the evidence (Padian and Chiappe 1998, Brochu andNorell 2000). ...
... Lastly, critics imply that such temporal disjunctions are rare or unexpected. But, as Padian and Chiappe (1998) point out, the fossil record of monotremes goes back less than 20 Ma, whereas the fossil record of therian mammals goes back 100 Ma. Yet, no one could credibly argue that this 80 my temporal disjunction could affect our confidence that monotremes are the sister group to all other extant mammals. ...
... The origin of the peculiar biology of birds has been investigated at several levels and from different functional and phylogenetic perspectives [1][2][3][4][5][6][7][8][9][10] . The evolution of the active flight of birds has been subjected to hierarchically nested analyses, which have reconstructed the sequence of adaptive regimes that shaped the avian bauplan [1][2][3]8,9 , have focused on the origin of locomotor modularity 4 , and have discussed the emergence of the anatomical novelties involved in powered flight [5][6][7]10 . ...
... The origin of the peculiar biology of birds has been investigated at several levels and from different functional and phylogenetic perspectives [1][2][3][4][5][6][7][8][9][10] . The evolution of the active flight of birds has been subjected to hierarchically nested analyses, which have reconstructed the sequence of adaptive regimes that shaped the avian bauplan [1][2][3]8,9 , have focused on the origin of locomotor modularity 4 , and have discussed the emergence of the anatomical novelties involved in powered flight [5][6][7]10 . In birds, the furcula (or wishbone) is a peculiar unpaired dermal element of the pectoral apparatus that articulates to each of the scapulocoracoids, working as a strut between the shoulders 11 . ...
Article
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The furcula is a distinctive element of the pectoral skeleton in birds, which strengthens the shoulder region to withstand the rigor of flight. Although its origin among theropod dinosaurs is now well-supported, the homology of the furcula relative to the elements of the tetrapod pectoral girdle (i.e., interclavicle vs clavicles) remains controversial. Here, we report the identification of the furcula in the birdlike theropod Halszkaraptor escuilliei . The bone is unique among furculae in non-avian dinosaurs in bearing a visceral articular facet in the hypocleideal end firmly joined to and overlapped by the sternal plates, a topographical pattern that supports the primary homology of the furcula with the interclavicle. The transformation of the interclavicle into the furcula in early theropods is correlated to the loss of the clavicles, and reinforced the interconnection between the contralateral scapulocoracoids, while relaxing the bridge between the scapulocoracoids with the sternum. The function of the forelimbs in theropod ancestors shifted from being a component of the locomotory quadrupedal module to an independent module specialized to grasping. The later evolution of novel locomotory modules among maniraptoran theropods, involving the forelimbs, drove the re-acquisition of a tighter connection between the scapulocoracoids and the interclavicle with the sternal complex.
... Modern birds comprise one of the most diverse clades of vertebrates alive today, yet members of this crown group, the Neornithes, are poorly represented in the fossil record before the Tertiary (Fountaine et al., 2005;Brocklehurst et al., 2012;Field et al., 2020). Instead, a wealth of pre-Tertiary fossils reveals the existence of numerous Mesozoic lineages outside of the crown clade Neornithes (Brusatte et al., 2015;Mayr 2016;Wang and Zhou 2017;Chiappe 2018;Chiappe and Bell 2020). These stem lineages represent an enormous diversity of forms, from the longlegged, cursorial Hollanda (Bell et al., 2010) to the long-winged, soaring Sapeornis , and from the small, flighted enantiornithines (O' Connor and Chiappe 2011;Liu et al., 2017) to the large, flightless hesperornithiforms (Bell and Chiappe 2016). ...
... These stem lineages represent an enormous diversity of forms, from the longlegged, cursorial Hollanda (Bell et al., 2010) to the long-winged, soaring Sapeornis , and from the small, flighted enantiornithines (O' Connor and Chiappe 2011;Liu et al., 2017) to the large, flightless hesperornithiforms (Bell and Chiappe 2016). This diversity in form has hinted at the possibility that collectively these stems birds could have approached the spectacular ecological diversity we see today in modern birds (Chiappe 2018). ...
Article
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Birds are one of the most diverse clades of extant terrestrial vertebrates, a diversity that first arose during the Mesozoic as a multitude of lineages of pre-neornithine (stem) birds appeared but did not survive into the Cenozoic Era. Modern birds (Neornithes) inhabit an extensive array of ecologically distinct habitats and have specific and varied foraging strategies. Likewise, the morphological disparity among Mesozoic lineages appears to underscore a significant degree of ecological diversity, yet attempts to determine lineage-specific ecologies have mainly been limited to superficial narratives. In recent years, numerous studies have used various morphometric proxies to interpret the paleoecology of Mesozoic bird lineages, but largely without evaluating the interplay between ecological and phylogenetic signals. Moreover, most studies of this sort transform the original data into logarithms to control dimensionality, underestimating the biases induced upon such transformations. The goal of this study is to quantitatively address the ecomorphology of crown-group Neornithes using a dense sample of raw forelimb and hindlimb measurements, and to examine if such results can be used to infer the ecologies of Mesozoic bird lineages. To that end, scaling of limb measurements and ecological data from modern birds was assessed statistically using phylogenetic comparative methods, followed by the inclusion of fossil taxa. A strong relationship was recovered between humerus and hindlimb allometric scaling and phylogeny. Our results indicate that while some ecological classes of modern birds can be discriminated from each other, phylogenetic signature can overwhelm ecological signal in morphometric data, potentially limiting the inferences that can be made from ecomorphological studies. Furthermore, we found differential scaling of leg bones among Early Cretaceous enantiornithines and ornithuromorphs, a result hinting that habitat partitioning among different lineages could be a pervasive phenomenon in avian evolution.
... Morphological studies on the skeleton and the plumage have forged a solid link between non-avialan coelurosaurians and birds building a well-accepted framework to understand the dinosaur-bird transition. [2][3][4] Recent works started to look beneath the surface and into the ultrastructure and chemistry in fossil feathers and bones and bring our understanding of this major transition to another new level. 1,[5][6][7][8][9][10][11][12] Chemistry of exquisitely preserved fossil animals including several iconic flying/gliding capable theropods www.at-spectrosc.com/as/article/pdf/202101001 ...
... At. Spectrosc. 2021, 42(1), [1][2][3][4][5][6][7][8][9][10][11] have been investigated to reveal information of their paleobiology and the fossilization process. 1,6,9,10,[12][13][14] Various chemical imaging techniques, e.g., Fourier-transform infrared (FTIR) spectroscopy, Raman spectroscopy, X-ray spectroscopy, and secondary-ion mass spectroscopy (SIMS), have been employed to track the molecular, elemental and isotopic information. ...
... 10 These objections should be understood in the context of critical discussion about the problems of character analysis and matrix construction with which morphological phylogenetics continues to be plagued (e.g., Poe and Wiens 2000;Wiens 2001;Rieppel andKearney 2002, 2007;Jenner 2003Jenner , 2004Nelson 2004;Wägele 2004;Mishler 2005;Kearney and Rieppel 2006;Wheeler 2007;Sereno 2007Sereno , 2009Williams and Ebach 2008;Assis 2009;Gill 2010, 2011;Brazeau 2011;Gill and Mooi 2011;Simões et al. 2016;Borkent 2018;Yu et al. 2021). Moreover, the "test of congruence" (Patterson 1982;de Pinna 1991), to which proponents of BADM routinely appeal when rejecting criticisms of the character data claimed to support it (e.g., see Padian and Chiappe 1998;Makovicky and Dyke 2001;Padian 2001;Prum 2003;Makovicky and Zanno 2011;Smith et al. 2015), is not a hypothetico-deductive or statistical test and constitutes at most a necessary but not sufficient criterion for the inference of homology (e.g., see Bryant 1989;Rieppel 1996;Haszprunar 1998;Wägele 2004;Vogt 2008;Fitzhugh 2012Fitzhugh , 2016aAssis 2015). It is unclear how Lakatosian criteria, designed to adjudicate between "research programs" based on their ability to generate "novel" predictions and "corroborations" (or lack) thereof, could satisfactorily address these essentially destructive, skeptical objections. ...
Article
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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.
... Nudds & Dyke, 2010;Voeten et al., 2018); however, feathers likely evolved for some purpose other than flight (Feo, Field & Prum, 2015;Lloyd et al., 2016) and were coopted to serve as integuments for powered flight later in the evolutionary history of birds (Persons & Currie, 2019). Despite the evolution of feathers pre-dating that of flight, birds subsequently evolved numerous physiological adaptations for flight, and all crown birds descended from an Feather function and the evolution of birds ancestor that was highly adapted for flight (Padian & Chiappe, 1998). ...
Article
Full-text available
The ability of feathers to perform many functions either simultaneously or at different times throughout the year or life of a bird is integral to the evolutionary history of birds. Many studies focus on single functions of feathers, but any given feather performs many functions over its lifetime. These functions necessarily interact with each other throughout the evolution and development of birds, so our knowledge of avian evolution is incomplete without understanding the multifunctionality of feathers, and how different functions may act synergistically or antagonistically during natural selection. Here, we review how feather functions interact with avian evolution, with a focus on recent technological and discovery‐based advances. By synthesising research into feather functions over hierarchical scales (pattern, arrangement, macrostructure, microstructure, nanostructure, molecules), we aim to provide a broad context for how the adaptability and multifunctionality of feathers have allowed birds to diversify into an astounding array of environments and life‐history strategies. We suggest that future research into avian evolution involving feather function should consider multiple aspects of a feather, including multiple functions, seasonal wear and renewal, and ecological or mechanical interactions. With this more holistic view, processes such as the evolution of avian coloration and flight can be understood in a broader and more nuanced context.
... 이러한 다양화는 1 억 3천 7십만 년에서 1억 2천만 년 전의 중국 북동부 제홀 생물군 화석 기록에서 확인할 수가 있다 Zhou, 2014 5천만 년 이상 진행된 진화의 결과이다 (Turner et al., 2007;Benson et al., 2014). 두 다리(이족) 보행자세, 경첩같은 발 목, 속이 빈 뼈, 새의 긴 S자형 목은 초기 공룡 조상에게 물 려 받았으며, 새의 furcula와 세 손가락형의 손(앞발)은 원시 수각류에서 처음 나타났고, 팔뚝을 몸에 대고 접는 능력은 조류와 밀접하게 관련된 파라비안(paravians)에서 나타났다 (Padian and Chiappe, 1998;Brusatte et al., 2010;Nesbitt, 2011;Xu et al., 2014). 길쭉한 앞발은 새의 날개로, 뒷다리 는 움직이는 활동의 대부분이 골반 관절보다 무릎관절에서 발생하는 기이한 구부린 뒷다리 자세로 진화한다 (Middleton and Gatesy, 2000;Allen et al., 2013). ...
... Actualmente se conoce que la reducción de la extremidad anterior se encuentra en tiranosáuridos (Osborn, 1906(Osborn, , 1916Bakker, 1986;Middleton y Gatesy, 2000;Carpenter, 2002;Brochu, 2003 ceratosaurios (Lavocat, 1955;Middleton y Gatesy, 2000;Coria et al., 2002;Tykoski y Rowe, 2004;Burch, 2017), carcharodontosáuridos (Holtz et al., 2004) y alvarezsaurios (Perle et al., 1993Novas, , 1997Middleton y Gatesy, 2000;Xu et al., 2013). El alargamiento de la extremidad anterior se da principalmente en el clado Paraves, cuyas extremidades anteriores son más largas que los miembros posteriores, y cuyas manos se hallan modificadas para el "vuelo por carrera" (Padian y Chiappe, 1998;Middleton y Gatesy, 2000). Esta amplia diversidad en el miembro anterior probablemente se utilizó durante el vuelo, la captura de presas o manipulación de alimentos, cópula, equilibrio, excavación, entre otras (Carpenter 1990;Carpenter y Smith, 1995;Middleton y Gatesy, 2000;Carpenter y Smith, 2001;Carpenter, 2002). ...
Thesis
This Doctoral Thesis presents an exhaustive review of the Patagonian alvarezsaurids (Dinosauria, Theropoda). It includes a detailed osteological description of specimens of Patagonykus puertai (Holotype, MCF-PVPH-37), cf. Patagonykus puertai (MCF-PVPH-38), Patagonykinae indet. (MCF-PVPH-102), Alvarezsaurus calvoi (Holotype, MUCPv-54), Achillesaurus manazzonei (Holotype, MACN-PV-RN 1116), Bonapartenykus ultimus (Holotype, MPCA 1290), and cf. Bonapartenykus ultimus (MPCN-PV 738). A phylogenetic analysis and a discussion about the taxonomic validity of the recognized species and the taxonomic assignment of the materials MCF-PVPH-38, MCF-PVPH-102 and MPCN-PV 738 are presented. Different evolutionary and paleobiological studies were carried out in order to elucidate functional and behavioral aspects. Alvarezsaurus calvoi (MUCPv-54), Achillesaurus manazzonei (MACN-PV-RN 1116), Patagonykus puertai (MCF-PVPH-37) and Bonapartenykus ultimus (MPCA 1290) are valid species due to the presence of many autapomorphies. In this sense, the hypothesis proposed by P. Makovicky and collaborators that Achillesaurus manazzonei is a junior synonym of Alvarezsaurus calvoi is rejected. Likewise, certain morphological evidence allows hypothesizing that Alvarezsaurus calvoi represents a growth stage earlier than skeletal maturity. Specimen MCF-PVPH-38 is referable as cf. Patagonykus puertai, while MCF-PVPH-102 is considered an indeterminate Patagonykinae. In turn, MPCN-PV 738 is assigned as cf. Bonapartenykus ultimus based on the little overlapping material with the Bonapartenykus ultimus holotype. The results obtained from the mineralogical characterization through the X-ray diffraction method of specimens MPCN-PV 738 and the holotype of Bonapartenykus ultimus (MPCA 1290), allow to suggest that both specimens come from the same geographical area and stratigraphic level. The phylogenetic analysis, which is based upon the matrix of Gianechini and collaborators of 2018 with the inclusion of proper characters, and the database of Xu and collaborators of 2018, recovered the South American members of Alvarezsauria, such as Alnashetri cerropoliciensis (Candeleros Formation; Cenomanian), Patagonykus puertai (Portezuelo Formation, Turonian-Coniacian), Alvarezsaurus calvoi and Achillesaurus manazzonei (Bajo de La Carpa Formation, Coniacian-Santonian), and Bonapartenykus ultimus (Allen Formation, Campanian-Maastrichtian), nesting within the family Alvarezsauridae. In this sense, the forms that come from the Bajo de La Carpa Formation (Coniacian-Santonian) are recovered at the base of the Alvarezsauridae clade, while Alnashetri cerropoliciensis nests as a non-Patagonykinae alvarezsaurid. Regarding the type specimens of Patagonykus puertai and Bonapartenykus ultimus, they are recovered as members of the Patagonykinae subclade, a group that is recovered as a sister taxon of Parvicursorinae, both nested within the Alvarezsauridae. In addition, the topology obtained allows discerning the pattern, rhythm and time of evolution of the highly strange and derived alvarezsaurian skeleton, concluding in a gradual evolution. The Bremer and Bootstrap supports of the nodes (Haplocheirus + Aorun), [Bannykus + (Tugulusaurus + Xiyunykus)], and Patagonykinae, show indices that represent very robust values for these nodes. Likewise, these values suggest that two endemic clades originated early in Asia, while one endemic clade is observed in Patagonia, i.e., Patagonykinae. The analysis of the directional trends of the Alvarezsauria clade, tested by means of a own database on body masses based on the Christiansen and Fariña method, subsequently calibrated with the group's phylogeny using the R software, shows two independent miniaturization events in the alvarezsaurid evolution, namely the former originating from the base of the Alvarezsauridae (sustained by Alvarezsaurus), and the latter within the Parvicursorinae. Analysis of the Alvarezsauria dentition reveals possible dental synapomorphies for the Alvarezsauria clade that should be tested in an integrative phylogenetic analysis. The general characterization of the forelimb and a partial reconstruction of the myology of alvarezsaurs demonstrate different configurations for Patagonykinae and Parvicursorinae. The multivariate analyzes carried out from the databases of Elissamburu and Vizcaíno, plus that of Cau and collaborators, show that the Patagonykinae would have had ranges of movements greater than those observed in Parvicursorinae, although the latter would have had a greater capacity to carry out more strenuous jobs. The morphometric analysis of the hindlimb and the use of the Snively and collaborators equations, show that the configuration of this element in Alvarezsauria is indicative of a highly cursorial lifestyle, as well as possible particular strategies for more efficient locomotion. The topology obtained in the phylogenetic analysis that was carried out in this Doctoral Thesis, allowed clarifying the ontogenetic changes observed in the ontogenetic series of the manual ungueal element II-2 within the clade Alvarezsauridae. In addition, the multivariate analysis carried out from the manual phalanx II-2 allows us to infer that alvarezsaurs could have performed functions such as hook-and-pull and piercing, where the arm would function as a single unit. The anatomy and myology of the alvarezsaurian tail show that the caudal vertebrae of alvarezsaurians exhibit a combination of derived osteological features that suggests functions unique among theropods, such as considerable dorsal and lateral movements, as well as exceptional abilities to support distal loading of their long tail without compromising stability and/or mobility.
... Skeletal remains of extinct organisms allow us to trace evolutionary changes in morphology across vast timescales and provide direct insight into major phenotypic transitions throughout the evolutionary history of vertebrates (Gauthier et al., 1988;Ahlberg and Milner, 1994;Padian and Chiappe, 1998;Thewissen et al., 2001;Daeschler et al., 2006;Shubin et al., 2006;Xu et al., 2010;Hsiang et al., 2015). Unfortunately, the fossil record is incomplete and often fragmentary (e.g., Fountaine et al., 2005;Alroy, 2010;Brocklehurst et al., 2012). ...
Article
Full-text available
Taphonomic and diagenetic processes inevitably distort the original skeletal morphology of fossil vertebrate remains. Key aspects of palaeobiological datasets may be directly impacted by such morphological deformation, such as taxonomic diagnoses and phylogenetic hypotheses, interpretations of the shape and orientation of anatomical structures, and assessments of interspecific and intraspecific variation. In order to overcome these ubiquitous challenges we present a novel reconstruction workflow combining retopology and retrodeformation, allowing the original morphology of both symmetrically and asymmetrically damaged areas of fossils to be reconstructed. As case studies, we present idealised three-dimensional reconstructions of the sternum of the crownward stem-bird Ichthyornis dispar, and cervical vertebrae of the diplodocid sauropod Galeamopus pabsti. Multiple Ichthyornis sterna were combined into a single, idealised composite representation through superimposition and alignment of retopologised models, and this composite was subsequently retrodeformed. The Galeamopus vertebrae were individually retrodeformed and symmetrised. Our workflow enabled us to quantify deformation of individual specimens with respect to our reconstructions, and to characterise global and local taphonomic deformation. Our workflow can be integrated with geometric morphometric approaches to enable quantitative morphological comparisons among multiple specimens, as well as quantitative interpolation of "mediotypes" of serially homologous elements such as missing vertebrae, haemal arches, or ribs.
... Birds are among the most easily defined and readily recognized categories of animals, due to the presence of the feather, which is unique to them. In addition to feathers, the development of forelimbs as wings, mostly in flight; feathered tail that serves for balancing, steering and lifting; toothless horny beak and skeleton exhibiting unique adaptations, mainly for flight and bipedal locomotion are characteristics of birds (Wallace et al. 1975;Padian et al. 1998). ...
Article
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Ecological investigation of Bird species diversity of the avifauna recorded during a survey of the Gudekote sloth bear Sanctuary, Bellary District, North Karnataka. The survey was carried out between March 2015 and April 2016. Transect count and point count methods were used to investigate the abundance of birds. Observation was conducted by periodically walking along the study area early in the morning and late in the afternoon. Different diversity indices and statistical methods were used to analyze data collected during the field survey. A total of 132 bird species and 50 families were recorded. Terrestrial habitat contributed much in terms of species composition (87%) than aquatic habitat (13%). Shannon's diversity index indicate that terrestrial habitat had higher species diversity (H' = 3.9996) than aquatic habitat (H' = 3.0717). The overall bird diversity in both terrestrial and aquatic was (H'=4.2669). Appropriate management of bird attractant sites is very important to discourage birds from the Gudekote sloth bear Sanctuary. A complete checklist of species recorded from the area is also given along with respective relative abundance levels recorded during the survey.
... These structures could play a role in the reinforcement of the beak as an adaptation to high stresses, especially as the beak in Psittacinae is extended. Association of tooth loss with replacement by a sharp beak (Chiappe, 2007) in theropod dinosaurs could suggest a possible phenomenon of covering of first-generation teeth by the developing ramphotheca as observed in parrots. ...
Article
Parrot embryos carry peculiar appendages at their developing beak that have been described as pseudoteeth. To better characterise the pattern of development responsible for the emergence of these dental appendages, we examined parrot embryos combining conventional histology and microtomography approaches. Using immunohistochemistry, we observed the epithelial and mesenchymal expression of several proteins involved in tooth development in mammals. Parrot pseudoteeth arose by epithelial and mesenchymal evagination, and their early development was similar to the ontogeny of scales and feathers. There was no enamel tissue, and the evaginations were surrounded by the rhamphotheca. In adults, the rhamphotheca covers entirely the appendages, now represented by bone evaginations, which were more numerous in the lower than in the upper beak, being similar to the osseous teeth of the fossil Pelagornithidae. These embryonic pseudoteeth resembled reptile's first-generation teeth and dental appendages of chicken talpid²mutants. Proteins involved in mammalian odontogenesis, such as SHH, BMP4, PITX2, and PAX9, were found to be generally expressed in beak epithelium and mesenchyme during parrot pseudoteeth development, with clusters of high-level expression in the pseudoteeth rudiments. This suggests that a similar, highly conserved gene expression programme gives rise to the appearance of odontode derivatives in numerous species, despite their divergent developmental paths. These results provide new insights into the development and evolution of odontode-derived structures in vertebrates. This article is protected by copyright. All rights reserved.
... Therefore, results of the present study suggest that WHO TEFs for both mammals and birds likely produce order of magnitude estimates of TEQs for reptiles, but WHO TEFs for birds are more comparable and therefore are recommended in the present study to be used in ecological risk assessments of reptiles. This comparability of relative potencies between reptiles and birds might be expected because modern cladistics consider birds to have descended from early reptiles (Mindell et al., 1999;Padian & Chiappe, 1998). However, growing evidence supports the potential for great differences in relative potencies among even closely related species (Cohen-Barnhouse et al., 2011b;Eisner et al., 2016). ...
Article
Reptiles represent the least-studied group of vertebrates with regards to ecotoxicology and no empirical toxicity data existed for dioxin-like chemicals (DLCs). This lack of toxicity data represents a significant uncertainty in ecological risk assessments of this taxon. Therefore, the present study assessed early-life sensitivity to select DLCs and developed relative potencies in the common snapping turtle (Chelydra serpentina) as a model reptile. Specifically, survival to hatch and incidence of pathologies were assessed in common snapping turtle exposed in ovo to serial concentrations of the prototypical reference congener 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), and three other DLCs of environmental relevance, namely, 2,3,4,7,8-pentachlorodibenzofuran (PeCDF), 2,3,7,8-tetrachlorodibenzofuran (TCDF), and 3,3',4,4',5-pentachlorobiphenyl (PCB 126). In ovo exposure to TCDD, PeCDF, TCDF, and PCB 126 caused a dose-dependent increase in early-life mortality, with median lethal doses (LD50s) of 14.9, 11.8, 29.6, and 185.9 pg/g-egg, respectively. Except for abnormal vasculature development, few pathologies were observed. Based on the measured LD50, common snapping turtle is more sensitive to TCDD in ovo than other species of oviparous vertebrates investigated to date. The potencies of PeCDF, TCDF, and PCB 126 relative to TCDD were 1.3, 0.5, and 0.08, respectively. These relative potencies are within an order of magnitude of World Health Organization (WHO) TCDD-equivalency factors (TEFs) for both mammals and birds supporting these TEFs as relevant for assessing ecological risk to reptiles. The great sensitivity to toxicities of the common snapping turtle, and potentially other species of reptiles, suggests a clear need for further investigation into the ecotoxicology of this taxon. Environ Toxicol Chem 2022;41:175-183. © 2021 SETAC.
... In this context, birds belong to Paraves (Sereno, 1997), a clade with mid to small-sized maniraptorans including the dromaeosaurids, troodontids, and emblematic fossils such as Archaeopteryx. A subsequent radiation along the Mesozoic involved the pygostylian avialans (Padian & Chiappe, 1998; Fig. 1), a clade encompassing the enantiornithine and ornithuromorphan birds (O'Connor et al., 2011). Some of the latter diverged into the crown group birds (i.e. ...
Article
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The dinosaurian origin of birds is one of the best documented events that palaeontology has contributed to the understanding of deep time evolution. This transition has been studied on multiple fossils using numerous multidisciplinary resources, including systematics, taxonomic, anatomical, morphological, biomechanical and molecular approaches. However, whereas deep time origins and phylogenetic relationships are robust, important nuances of this transition’s dynamics remain controversial. In particular, the fossil record of several maniraptoran groups clearly shows that aerial locomotion was developed before an ‘avialization’ (i.e., before the first divergence towards avialans), thus earlier than presumed. Although aspects as important as miniaturization and the acquisition of several anatomical and morphological modifications are key factors determining such evolutionary transition, understanding this macroevolutionary trend also involves to seize the evolution of developmental systems, which requires assessing the morphological expression of integration and modularity of the locomotor apparatus throughout time. This is so because, as it happened in other flying vertebrate taxa such as pterosaurs and bats, the transformation of the maniraptoran forelimbs into flying locomotor modules must not only have involved a gradual anatomical transformation, but also a complete developmental re-patterning of the integration scheme between them and the hindlimbs. Here, we review the most relevant aspects of limb morphological transformation during the so-called ‘dinosaur-bird’ transition to stress the importance of assessing the role of modularity and morphological integration in such macroevolutionary transition, which ultimately involves the origins of flight in dinosaurs.
... Segundo Adrian Desmond (2008, p. 431) A ideia de que aves são uma linhagem dentro de dinossauros é um conceito amplamente difundido na literatura atual (e.g. SERENO, 2004;CHIAPPE, 2007). Contudo, essa percepção é fruto da tese idealizada em sua maioria por Thomas Huxley, na qual apontou a existência de uma relação de parentesco entre esses dois grupos. ...
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Este trabalho consiste em uma tradução do artigo “On the Animals which are most nearly intermediate between Birds and the Reptiles”, de autoria de Thomas Huxley (1825-1895), publicado no Annals and Magazine of Natural History, em fevereiro de 1868. Nesse artigo, Thomas Henry Huxley (1825-1895) lidou com a hipótese da existência de uma relação de parentesco entre répteis e aves após ter observado diversas similaridades entre dois fósseis pertencentes a esses grupos: Compsognathus e Archeopteryx. Apesar das inúmeras evidências apontadas por Huxley, e outros pesquisadores, a hipótese de que aves descendiam de dinossauros perdeu força na década de 1920. Só seria retomada na década de 1970, e desde então é consenso na comunidade científica.
... The results are consistently interpreted as further confirmation of Ostrom's hypothesis, that birds evolved from small theropod dinosaurs. The laterally flexing wrist and modern-type feathers evolved in theropods for reasons unrelated to birds or flight (Padian andChiappe 1998, Clarke 2013). ...
Article
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... However, how early birds and feathered dinosaurs acquired their flight capabilities and the detailed evolutionary process of flight remain debatable [3][4][5]41]. Among extant birds' anatomical features, the high carina, rigid trunk, healed pelvis, and asymmetric feathers are the structures critical for flight [3,42]. In contrast, confuciusornithids possessed only a relatively primitive flight-related structure. ...
Article
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Eastern Asia can be regarded as a dynamic environment during the Early Cretaceous in which the whole biota was complex and diverse, so the differentiation of early birds was also pronounced in this period. Confuciusornithids only uncovered from Eastern Asia, are an important early bird group for revealing the origin and early evolution of avian flight. However, results on confuciusornithid flight capabilities mainly come from qualitative analysis or speculation and analogism because of insufficient information from fossils, limited analogues in living birds, and no rigorous biomechanical testing. As an essential and popular tool in quantitative simulation and analysis, computational fluid dynamics (CFD) has major advantages over other techniques and has been well developed in recent years to solve general morphological-functional problems in palaeontolog-ical research. CFD is beneficial for studying the flight capability of confuciusornithids and will provide new quantitative evidence for the origin and evolution of early bird flight. In addition, we expect that interdisciplinary, exploratory, and tentative work will soon be applied in other similar studies, which will allow us to develop a quantitative method that can be applied effectively in functional-morphological analyses.
... Birds are among the most easily defined and readily recognized categories of animals, due to the presence of the feather, which is unique to them. In addition to feathers, the development of forelimbs as wings, mostly in flight; feathered tail that serves for balancing, steering and lifting; toothless horny beak and skeleton exhibiting unique adaptations, mainly for flight and bipedal locomotion are characteristics of birds (Wallace et al. 1975;Padian et al. 1998). ...
Article
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Ecological investigation of Bird species diversity of the avifauna recorded during a survey of the Gudekote sloth bear Sanctuary, Bellary District, North Karnataka. The survey was carried out between March 2015 and April 2016. Transect count and point count methods were used to investigate the abundance of birds. Observation was conducted by periodically walking along the study area early in the morning and late in the afternoon. Different diversity indices and statistical methods were used to analyze data collected during the field survey. A total of 132 bird species and 50 families were recorded. Terrestrial habitat contributed much in terms of species composition (87%) than aquatic habitat (13%). Shannon's diversity index indicate that terrestrial habitat had higher species diversity (H' = 3.9996) than aquatic habitat (H' = 3.0717). The overall bird diversity in both terrestrial and aquatic was (H'=4.2669). Appropriate management of bird attractant sites is very important to discourage birds from the Gudekote sloth bear Sanctuary. A complete checklist of species recorded from the area is also given along with respective relative abundance levels recorded during the survey.
... Although the knowledge of the anatomy of alvarezsaurians has been greatly improved by many recently discovered alvarezsaurid species, the internal phylogenetic relationships of Alvarezsauria remain labile (Perle et al., 1993(Perle et al., , 1994Zhou, 1995;Chiappe et al., 1996Chiappe et al., , 1997Novas, 1997;Hutchinson and Chiappe, 1998;Sereno, 2001;Suzuki et al., 2002;Martinelli and Vera, 2007;Alifanov and Barsbold, 2009;Longrich and Currie, 2009;Choiniere et al., 2010;Xu et al., 2010Xu et al., , 2011Xu et al., , 2013Nesbitt et al., 2011;Agnolin et al., 2012;Makovicky et al., 2012;Turner et al., 2012;Choiniere et al., 2010Choiniere et al., , 2013Pittman and Stiegler, 2015;Gianechini et al., 2018;Lü et al., 2018;Xu et al., 2018, Qin et al., 2019Hartmann et al., 2019). Compared to other maniraptoran lineages, alvarezsaurians occupied only the lower ranges of the body size spectrum (Fig. 1), from the~0.43 m long Parvicursor remotus (Choiniere et al., 2010;Pittman and Stiegler, 2015) to the~2.3 m long Haplocheirus sollers (Choiniere et al., 2010;Pittman and Stiegler, 2015). ...
Article
The anatomy of the alvarezsaurian tail has received relatively little attention in the paleontological literature, even though it shows a peculiar combination of anatomical characteristics that are unique among theropod dinosaurs. Nearly complete, informative tails are known from early-branching, intermediate, and late-branching taxa, allowing for robust inferences about their evolution. The alvarezsaurian tail is notable in being the longest among maniraptoran theropods, both in number of caudal vertebrae and proportional length. We examined the comparative anatomy and myology of the tail, and performed a cladistic analysis on a tail-character-based data matrix that provided a general framework for reconstructing alvarezsaurian tail evolution. Our results show that caudal vertebrae of alvarezsaurians have a combination of derived osteological features, intervertebral joint morphology, and inferred musculature, which together suggest that the tail possessed a unique function among theropods. We interpret these features as indicators of an exceptional capacity to change rotational inertia. The form and function of the tail, in combination with the fossorial forelimb, suggests that alvarezsaurians had an ecological niche similar to today's aardvark, pangolins and anteaters.
... Although the idea that birds originated from theropods has been supported by more and more new evidences, issues such as how early birds acquired flight capabilities are still more controversial [9,[18][19]49]. The anatomical and morphological features of living birds indicate that large carina, longstemmed wrists, rigid trunk, healing pelvis, developed pygostyle, and asymmetric feathers are the key structures adapted to flight [19,50]. Confuciusornithidae only developed relatively primitive flight structures, and their morphological characteristics are far from those of extant birds [6,11,15,17], and it is difficult to analyze them one by one with living animals. ...
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We investigated numerous related literatures of confuciusornithid birds and summarized in terms of environmental background, research status (includ-ing morphology, evolutionary characteristics, and flight capability) and prospects. It is expected to generate a new idea and perspective for the study of Early Cretaceous paleontology and paleoenviron-mentology. Confuciusornithidae is an important group of fossil birds, which has developed tremendously in north China and other east Asian regions during Early Cretaceous. They are studied deeper than many other birds, because of the significance of evolutionary status and many exquisite specimens unmatched by other birds in the same period. And confuciusornithid birds are also the focus of pale-ornithology and paleoenvironment in the reason of their coevolutionary relation. By now, the flight capability of Confuciusornithidae has not been proved, though it was one group of fossil birds with large feathers. There are also no extant birds with aerodynamic feathers on their hindlimbs. Therefore, the flight capability has not been knowed by accurate comparsion at present; the previous conclusions came from morphological analogy and functional speculation; and the research on the origin and evolution of bird flight is also limited by that. Fortunately , hindlimb feathers with aerodynamic characteristics have been found on the Deinonychus and other early birds in the past two decades, which strongly supports hindlimbs are important in the origin of birds flight. And the hindlimbs of birds play an irreplaceable role in aerial and ground locomotion. As a consequence, the hindlimbs aerodynamic performance of confuciusornithid birds will be a breakthrough in the future research. In addation, the proceeding of the digital revolution pleases us immensely that the advancements of computer technologies make the quantitative studies of birds flight more accessible. In the long run, the research of the life habits of Confuciusornithidae can provide valuable data for the coevolution of paleornithology and paleoenvironment in Early Cretaceous.
... Thus, flightless birds are often leggy compared with their volant relatives. Leg-dominated, flightless birds have historically been successfulin some cases becoming apex predators [103][104][105] and they are not the only birds with permanently reduced wings. Although we have traditionally categorized birds as flying or flightless, this binary terminology actually masks tremendous natural variation in anatomy and flight capacity. ...
Article
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A major challenge to Darwinian evolution is explaining 'rudimentary' organs. This is particularly relevant to birds: rudimentary wings occur in fossils, as well as in developing, molting, and flight-impaired birds. Evidence shows that young birds flap small wings to improve locomotion and transition to flight. Although small wings also occur in adults, their potential role in locomotion is rarely considered. Here we describe the prevalence of rudimentary wings in extant birds, and how wings wax and wane on many timescales. This waxing and waning is integral to the avian clade and offers a rich arena for exploring links between form, function, performance, behavior, ecology, and evolution. Although our understanding is nascent, birds clearly show that rudimentary structures can enhance performance and survival.
... Morphological studies on the skeleton and the plumage have forged a solid link between non-avialan coelurosaurians and birds, building a well-accepted framework for understanding the dinosaur-bird transition. [2][3][4] Recent works started to look beneath the surface and into the ultrastructure and chemistry of fossil feathers and bones, and bring our understanding of this major transition to a new level. 1,[5][6][7][8][9][10][11][12] The chemistry of exquisitely preserved fossil animals, including several iconic flying/gliding theropods, have been investigated to reveal information on their paleobiology and the fossilization process. ...
Article
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Jianianhualong tengi is a key taxon for understanding the evolution of pennaceous feathers as well as of troodontid theropods. It is known by only the holotype, which was recovered from the Lower Cretaceous Yixian Formation of western Liaoning, China. In this study, we carried out a large-area micro-X-Ray fluorescence (micro-XRF) analysis of the holotype of Jianianhualong tengi via a Brucker M6 Jetstream mobile XRF scanner. The elemental distribution measurements of the specimen show an enrichment of typical bone-associated elements, such as S, P and Ca, which allows to visualize the fossil structure. Additionally, the bones are enriched with several heavier elements, such as Sr, Th, Y and Ce relative to the surrounding rocks. The enrichment is most likely associated to secondary mineralization and the phosphates from the bones. Interestingly, the plumage shape correlates with an enrichment in elements, such as Cu, Ni and Ti, consistent with the findings of a previous study 1 on Archaeopteryx using synchrotron imaging. Elemental variations among the skeleton, the unguis and the sheath blade further indicate their possible compositional or ultrastructural differences, providing new biological and taphonomic information on the fossilized keratinous structures. An in-situ and nondestructive micro-XRF analysis is currently the most ideal way to map the chemistry of meter-sized fossils and has so far been mainly restricted to small samples. Micro-spatial chemical analysis of larger samples usually required a synchrotron facility. Our study demonstrated that a laboratory-based large-area micro-XRF scanner can provide a practical tool for the study of large specimens, thus allowing to collect full chemical data in order to obtain a better understanding of evolutionary and taphonomic processes.
... Indeed, it may be that the more substantial the innovation, the more substantial the trade-off. As an example, the evolution of powered flight clearly affected bird diversification in positive ways (Padian & Chiappe, 1998), but it also introduced a constraint on body mass due to metabolic and performance demands (McNab, 1994;Tobalske & Dial, 2000;Elliot et al., 2013). There is a tendency to focus on the enabling consequences of functional innovations; however, the potency of trade-offs may be a major factor in shaping the diversity of macroevolutionary outcomes from life's innovations. ...
Article
Innovations may provide access to new resources but often result in significant trade-offs. Pharyngognathy is a classic pharyngeal jaw innovation in which the left and right lower pharyngeal jaw (LPJ) bones are united into a single structure, producing a strong bite but reduced gape. Throughout cichlids, pharyngeal suturing occurs along the entire medial border between LPJ bones, except in peacock bass (Cichla), where these bones are connected by ligaments only in their anterior region. We show that this limited attachment permits the jaw bones to spread apart and we link this feature to an increase in pharyngeal gape that is comparable to non-pharyngognathous species. The capacity of the LPJ bones to spread apart is strongest in juveniles and is mostly lost during development. Juvenile Cichla exhibit size-specific pharyngeal gape similar to non-pharyngognathous percomorphs; however, adults exhibit pharyngeal gape on par with other predatory cichlids. Relaxation of pharyngeal suturing offsets a major deleterious consequence of pharyngognathy by reducing gape limitation and we propose this may accelerate the ontogenetic transition to piscivory. Partial reversal of the classic cichlid pharyngeal jaw innovation highlights the functional trade-offs that often accompany innovations and may be a major cause of variation in their macroevolutionary consequences.
... Obviously, despite their evolution, ecological niches are not wildly variable over evolutionary time periods. That is, physiologically challenging environmental realms such as the air and land have been invaded only a relatively few times (Gordon and Olson 1994, Padian and Chiappe 1998, Larson 1982. On the fl ip side of the coin, however, Eltonian and Grinnellian niches, and major morphological and physiological traits that determine, for example, trophic position or other fundamental ecological adaptations, have obviously changed on some scale: marine organisms invaded land at several points in evolutionary history, and terrestrial clades have even invaded back into marine environments (e.g., sea snakes and whales). ...
Chapter
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This chapter considers a concept of niche that emphasizes multidimensional spaces of scenopoetic variables and provides a natural connection to the study of geographic distributions of species. It first explains the relations between environmental and geographic spaces before discussing the use of equations to link spatially explicit population growth patterns to variation in the ecological characteristics of species. It then describes the BAM diagram, a Venn diagram that displays the joint fulfillment in geographic space of three sets of conditions that together determine species distribution: biotic conditions, abiotic conditions, and movement of the species. The chapter also explores the spatial resolution of scenopoetic variables, estimation of the fundamental and existing fundamental niches, the biotically reduced niche, and caveats about reducing Grinnellian niches and the Eltonian Noise Hypothesis. Finally, it shows how distributional areas and ecological niches can be estimated.
... Indeed, it may be that the more substantial the innovation, the more substantial the trade-off. As an example, the evolution of powered flight clearly affected bird diversification in positive ways (Padian & Chiappe, 1998), but it also introduced a constraint on body mass due to metabolic and performance demands (McNab, 1994;Tobalske & Dial, 2000;Elliot et al., 2013). There is a tendency to focus on the enabling consequences of functional innovations; however, the potency of trade-offs may be a major factor in shaping the diversity of macroevolutionary outcomes from life's innovations. ...
Article
Innovations may provide access to new resources but often result in significant trade-offs. Pharyngognathy is a classic pharyngeal jaw innovation in which the left and right lower pharyngeal jaw (LPJ) bones are united into a single structure, producing a strong bite but reduced gape. Throughout cichlids, pharyngeal suturing occurs along the entire medial border between LPJ bones, except in peacock bass (Cichla), where these bones are connected by ligaments only in their anterior region. We show that this limited attachment permits the jaw bones to spread apart and we link this feature to an increase in pharyngeal gape that is comparable to non-pharyngognathous species. The capacity of the LPJ bones to spread apart is strongest in juveniles and is mostly lost during development. Juvenile Cichla exhibit size-specific pharyngeal gape similar to non-pharyngognathous percomorphs; however, adults exhibit pharyngeal gape on par with other predatory cichlids. Relaxation of pharyngeal suturing offsets a major deleterious consequence of pharyngognathy by reducing gape limitation and we propose this may accelerate the ontogenetic transition to piscivory. Partial reversal of the classic cichlid pharyngeal jaw innovation highlights the functional trade-offs that often accompany innovations and may be a major cause of variation in their macroevolutionary consequences.
... Modern birds are the only living representatives of the maniraptoran theropod radiation (Gauthier, 1986;Padian and Chiappe, 1998;Sereno, 1999;Zhou, 2004;Norell and Xu, 2005). One of the most intriguing events of the macroevolutionary transition leading to anatomically modern birds is the transformation of the archetypal grasping forelimb of nonavialan maniraptoran theropods into the forelimb of modern birds ( fig. ...
Article
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Multiple factors involved in the evolutionary transformation of the manus across the maniraptoran radiation, including its current morphology in modern birds, remain unexplored. Specifically, the morphological disparity of the manus has never been studied quantitatively, and there are no hypotheses about the possible mechanisms and constraints underlying its evolution. Morphological disparity is best studied with shape-analysis tools based on Procrustes methods, because they guarantee the independence of shape from size while depicting the results in expressive graphics. However, this methodology compares fixed configurations of coordinates, preventing their use in highly articulated and movable structures such as the maniraptoran manus. Here, we propose a new protocol, the one-dimensional Procrustes analysis (OPA), for transforming the chord lengths of these bones into unidimensional Cartesian coordinates, enabling treatment of the data under the operational advantages of the Procrustes methods. Our results applying this new method on a sample encompassing 174 maniraptoran dinosaurs manus, including 79 fossils (both avialan and nonavialan taxa) and 95 extant paleognathans and neognathans, document the morphological transition between early-diverging maniraptorans, nonavialan paravians, and birds over morphospace, highlighting an unexpectedly low disparity in the crown group when compared to early-diverging taxa. Within this transition, we show a common trend of proportional reduction and loss of distal elements, mostly in the minor and alular digits. Furthermore, our study reveals an allometric pattern characterizing manus morphological variation between early-diverging maniraptorans and enantiornithine avialans that disappears in crown birds and their closest early-diverging counterparts. This previously unnoticed allometric trend suggests a complex interplay of developmental, functional, and historical constraints in the evolution of the maniraptoran manus.
... There remains controversy over the origins of bird flight. Prior positions have often been one of a 'ground-up' progression to flapping flight from terrestrial ancestors, or a 'trees-down' progression from gliding, arboreal ancestors (although any animal that had reached the ground through gliding would need to gain height again and some form of flapping-climbing would integrate both hypotheses) [72,73]. Resolving these competing ideas is generating an ever better understanding of the functional anatomy of these animals [25] (see Outstanding Questions). ...
Article
Animal flight is ecologically important and has a long evolutionary history. It has evolved independently in many distantly related clades of animals. Powered flight has evolved only three times in vertebrates, making it evolutionarily rare. Major recent fossil discoveries have provided key data on fossil flying vertebrates and critical insights regarding the evolution and different arrangements of animal flight surfaces. Combined with new methodologies, these discoveries have paved the way for potentially expanding biomimetic and biologically inspired designs to incorporate lessons from fossil taxa. Here, we review the latest knowledge and literature regarding flight performance in fossil vertebrates. We then synthesise key elements to provide an overview of those cases where fossil flyers might provide new insights for applied sciences.
... Birds all evolved from a single common ancestor [1,2]. Flight is the most striking feature distinguishing birds from all other vertebrates, and is also the main means of birds hunting, nesting and predator defending [3]. ...
Article
Most of owls are nocturnal raptor and usually use their soft and fluffy feathers to flight silently to catch prey while other diurnal raptors prefer fierce attack and swift flight. For energy cost of these different hunting strategies can be greatly different, we speculate that mitochondrial gene of owls may undergo a different evolution pattern following raptors evolution. To test our hypothesis, we sequenced the mtDNA genome of Otus sunia and calculated the ratio of nonsynonymous to synonymous nucleotide substitutions (ω, Ka/Ks, dN/dS) of raptors. The mtDNA genome of O. sunia was 17,609 bp in length, containing 13 PCGs, 2 ribosomal RNAs, 22 transfer RNAs and a control region. Secondly structure of tRNAs and rRNAs were predicted and conserved sequence blocks (CSBs) on control region were identified. The Bayesian inference tree and maximum likelihood tree based on 13 PCGs and 2 rRNAs suggested the owls were related to other raptors. Finally, calculation of ω-values of each owls and other raptors mtDNA PCGs indicated that owls accumulated more nonsynonymous nucleotide substitutions relative to synonymous substitutions compared to other raptors. For mtDNA PCGs associated with energy metabolism, this finding may reveal the degeneration of flight abilities of owls.
... Questi sono generalmente presenti nei «rettili» ectotermi (a sinistra) e negli uccelli e mammiferi endotermi (a destra). Modi cato daChiappe (2007). ...
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Come possiamo mettere insieme lo studio dei geni, degli embrioni e dei fossili? I fossili possono dimostrare dei cambiamenti evolutivi nelle modalità riproduttive? Come hanno influenzato lo sviluppo degli organismi marini i cambiamenti della composizione chimica degli oceani? Cosa ci rivela la microstruttura delle ossa e dei denti a proposito del raggiungimento della maturità, della longevità e dei cambiamenti nei cicli di crescita degli organismi estinti? Embrioni nel tempo profondo discute questi e altri argomenti proponendo una sintesi critica di concetti che provengono dalla anatomia comparata, dall’ecologia e dalla genetica dello sviluppo. Questo libro illustra come i fossili possano fornire informazioni non solo sulla anatomia degli adulti ma anche sulla life history degli individui in diversi momenti della loro vita. Le trasformazioni che avvengono durante la vita di un organismo e i meccanismi che le rendono possibili, uno degli argomenti principali della biologia moderna, sono discusse in modo comparato e integrato, rivelando che i fossili offrono una visione unica sulle idee centrali dell’evoluzione e dello sviluppo.
... One dromaeosaur (Halszkaraptor) plots outside the 'predatory' morphospace despite having a carnivorous lifestyle, which supports our interpretation of the measured 'predatory' morphospace as, more specifically, 'predatory-perching'. Halszkaraptor may represent an abnormal data point as it has been interpreted as a semi-aquatic animal [37], but as semiaquatic birds clustered with terrestrial taxa (see S1 Table) we expect the halszkaraptorine claw should not possess unusual adaptations. Halzskaraptor, one anchiornithid Eosinopteryx, and the troodontid Borogovia received robust terrestrial classifications (Fig 4, Table 5) consistent with osteological features and findings of past studies [28,30,37], and so these predictions suggest phylogenetically high curvatures of paravian claws may not influence false confirmations of arboreality as has been previously suggested [87][88][89]. ...
Article
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Claws are involved in a number of behaviours including locomotion and prey capture, and as a result animals evolve claw morphologies that enable these functions. Past authors have found geometry of the keratinous sheath of the claw to correlate with mode of life for extant birds and squamates; this relationship has frequently been cited to infer lifestyles for Mesozoic theropods including Archaeopteryx. However, many fossil claws lack keratinous sheaths and thus cannot be analysed using current methods. As the ungual phalanx within the claw is more commonly preserved in the fossil record, geometry of this bone may provide a more useful metric for paleontological analysis. In this study, ungual bones of 108 birds and 5 squamates were imaged using X-ray techniques and a relationship was found between curvatures of the ungual bone within the claw of pedal digit III and four modes of life; ground-dwelling, perching, predatory, and scansorial; using linear discriminant analysis with weighted accuracy equal to 0.79. Our model predicts arboreal lifestyles for Archaeopteryx and Microraptor and a predatory ecology for Confuciusornis. These findings demonstrate the utility of our model in answering questions of palaeoecology, the theropod-bird transition, and the evolution of avian flight. Though the metric exhibits a strong correlation with lifestyle, morphospaces for PD-III curvatures overlap and so this metric should be considered alongside additional evidence.
... Theropods are a lineage of bipedal dinosaurs including birds and their most recent common ancestors (e.g., Padian and Chiappe, 1998;Chiappe and Witmer, 2002;Long and Schouten, 2008;Naish, 2012). Although non-avian theropods were mostly carnivores, there is abundant evidence for substantial trophic variation within the group, including herbivory (e.g., Kobayashi et al., 1999;Zanno et al., 2009;Sander et al., 2010;Zanno and Makovicky, 2011), omnivory (e.g., Holtz et al., 1998) and piscivory (e.g., Charig and Milner, 1997;Amiot et al., 2010;Xing et al., 2013b). ...
Article
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Isolated theropod teeth are some of the most common fossils in the dinosaur fossil record and are continually reported in the literature. Recently developed quantitative methods have improved our ability to test the affinities of isolated teeth in a repeatable framework. But in most studies, teeth are diagnosed on qualitative characters. This can be problematic because the distribution of theropod dental characters is still poorly documented, and often restricted to one lineage. To help in the identification of isolated theropod teeth, and to more rigorously evaluate their taxonomic and phylogenetic potential, we evaluated dental features in two ways. We first analyzed the distribution of 34 qualitative dental characters in a broad sample of taxa. Functional properties for each dental feature were included to assess how functional similarity generates homoplasy. We then compiled a quantitative data matrix of 145 dental characters for 97 saurischian taxa. The latter was used to assess the degree of homoplasy of qualitative dental characters, address longstanding questions on the taxonomic and biostratigraphic value of theropod teeth, and explore the major evolutionary trends in the theropod dentition. In smaller phylogenetic datasets for Theropoda, dental characters exhibit higher levels of homoplasy than non-dental characters, yet they still provide useful grouping information and optimize as local synapomorphies of smaller clades. In broader phylogenetic datasets, the degree of homoplasy displayed by dental and non-dental characters is not significantly different. Dental features on crown ornamentations, enamel texture, and tooth microstructure have significantly less homoplasy than other dental features and can be used to identify many theropod taxa to ‘family’ or ’sub-family’ level, and some taxa to genus or species. These features should, therefore, be a priority for investigations seeking to classify isolated teeth. Our observations improve the taxonomic utility of theropod teeth and in some cases can help make isolated teeth useful as biostratigraphic markers. This proposed list of dental features in theropods should, therefore, facilitate future studies on the systematic paleontology of isolated teeth.
... All species are forestdwelling with four forms (Atelornis crossleyi, A. pittoides, Brachypteracias leptosomus, and B. squa-migera) occurring in humid forests dominating east and central highlands, and the fifth species (Uratelornis chimaera) in the spiny bush of the dry southwest (Langrand 1990). Both Brodkorb (1971) and Olson (1985) noted that there is no known fossil history of ground rollers. However, well-preserved material from the Eocene Messel Formation of Germany was said by Martin (1983) and Feduccia (1999) to contain an example of the Brachypteraciidae. ...
Article
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We studied relationships of five extant members of the endemic Malagasy family Brachypteraciidae, the ground rollers, using several mitochondrial genes (cytochrome-b, NADH dehydrogenase 2, 12S ribosomal RNA, and cytochrome oxidase I). As outgroups, we used other coraciiforms including the Cuckoo Roller (Family Leptosomatidae, Leptosomus discolor), several true rollers (Corcaciidae) and a tody (Todidae). Partial sequences of the Long-tailed Ground Roller (Uratelornis chimaera) were obtained from toe pad samples taken off museum specimens. For a combined data set of all genes, Kimura two-parameter distances between sequences of the five ground roller species were high, averaging 11% divergence. For several species, samples were available from widely separated geographic regions and intraspecific sequence divergence was low (≤0.8%). Unweighted and weighted parsimony and maximum-likelihood analyses consistently recovered monophyly of the family, a sister relationship between Brachypteraciidae and Coraciidae, and monophyly of one of three currently recognized ground roller genera (Atelornis). At the base of the Brachypteraciidae clade, we could not fully resolve relationships between Uratelornis and two species currently placed in Brachypteracias. Because of the uncertainty of basal nodes in our phylogenetic reconstructions, we recommend returning B. squamigera to the monotypic genus Geobiastes. High levels of divergence among ground rollers are similar to levels found in other avian groups endemic to Madagascar. However, we suggest that molecular divergences appear far too low to be consistent with mid-Eocene fossils attributed to the family.
... The density (specific gravity) of fresh brain tissue is close to one in mammals, birds, and reptiles [Jerison, 1973;Hurlburt, 1996]. To calculate the brain volume of the reptile and bird species in our sample we used a common specific gravity of 1.036 g mL -1 [Padian and Chiappe, 1998;Iwaniuk and Nelson, 2002;Domínguez Alonso et al., 2004]. Body volumes for reptiles were calculated from body mass data using a conservative overall tissue specific gravity of 1.025 g mL -1 , which is the average of specific gravity values for eight species available in the literature [Colbert, 1962;Jackson, 1969;Hurlburt, 1999;Hochscheid et al., 2003;Peterson and Gomez, 2008]. ...
Article
Body size correlates with most structural and functional components of an organism’s phenotype – brain size being a prime example of allometric scaling with animal size. Therefore, comparative studies of brain evolution in vertebrates rely on controlling for the scaling effects of body size variation on brain size variation by calculating brain weight/body weight ratios. Differences in the brain size-body size relationship between taxa are usually interpreted as differences in selection acting on the brain or its components, while selection pressures acting on body size, which are among the most prevalent in nature, are rarely acknowledged, leading to conflicting and confusing conclusions. We address these problems by comparing brain-body relationships from across >1,000 species of birds and non-avian reptiles. Relative brain size in birds is often assumed to be 10 times larger than in reptiles of similar body size. We examine how differences in the specific gravity of body tissues and in body design (e.g., presence/absence of a tail or a dense shell) between these two groups can affect estimates of relative brain size. Using phylogenetic comparative analyses, we show that the gap in relative brain size between birds and reptiles has been grossly exaggerated. Our results highlight the need to take into account differences between taxa arising from selection pressures affecting body size and design, and call into question the widespread misconception that reptile brains are small and incapable of supporting sophisticated behavior and cognition.
... The oldest fossil of what is considered to be the first ever bird, Archaeopteryx lithographica (see Figure 1), was found in 1860 in late Jurassic deposits near Solnhofen, Germany and dated to being about 150 million years of age (Ericson, 2008;Chiappe, 2009). It has long been accepted that Archaeopteryx was a transitional form between birds and reptiles, which is evident in a number of ways; perhaps most obviously in the similarities between reptilian scales and the scales and feathers of birds (Padian & Chiappe, 1998). Furthermore, birds retain the single occipital condyles also found in reptiles, and both birds and reptiles have a single middle ear bone (ossicle) whereas mammals have three suggesting common ancestry between birds and reptiles. ...
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Little is known about the effects of increased human activities on Cambodian avifauna and the extent and speed of the decline in bird species. This study aims to compare the biodiversity value of a currently pristine forest versus that of a previously disturbed forest, in order to guide the development of priorities in conservation planning for these sites. The study hypothesized that because selective logging will target forest patches containing large luxury tree species, these forest patches, although disturbed, may represent crucial biodiversity sites in addition to currently pristine forest patches. The study was undertaken in Phnom Samkos Wildlife Sanctuary from February to April 2011. Point-counts and mist-nets were used to census birds within two representative sites. To ensure valid comparison, sampling methods and effort were standardized in each forest habitat. A total of 1,437 bird individuals of 100 species representing 33 families were seen and/or captured. The results showed that the bird community in the disturbed habitat was significantly higher than in the pristine habitat in term of actual number species, the number of individuals and Simpson’s diversity index, but estimated species richness was not different. 31 of the total 100 species including endangered groups of hornbill and partridge were found at both habitats but with higher abundance in the pristine habitat. This may indicate that these species were relatively mal-adapted to human disturbances or may be increasingly threatened if the degree of disturbance is widespread. The chestnut-headed partridge, Arborophila cambodiana was more abundant in the pristine habitat which shows that this species endemic to Cardamom Mountains is likely negatively associated with disturbance. The results also found that the number of individual birds detected by point-count was significantly higher than captured by mist-net, while the number of species did not differ. The majority of birds found in significantly higher abundance in the disturbed habitat are suggested to be associated with forest dominated by larger trees, or with higher diversity of trees which provide a rich food source. Point-count is more effective to census bird than mist-netting, but both methods are recommended to be used together in order to get a reliable and comprehensive comparison.
... Dinosaurs have survived as birds to the present day, and this idea is universal (Padian and Chiappe 1998;Fastovsky and Weishampel 2005;Brusatte et al. 2015). Currently, there are around 10,500 species of birds in the world (Tudge 2008). ...
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Animals at the neonatal stage have to eat more to support better growth and health. However, it is difficult to understand the mechanism of feeding during an early stage of life in the brain of the rodent model. Chickens are precocial and they can look for their food by themselves right after hatching. Neonatal chicks have a relatively large-sized brain; therefore, the drugs are easy to administer centrally and changes in food intake can be clearly monitored. Sleeping status, which affects food intake, can be estimated from the posture. The closest vertebrate outgroup to mammals is birds, but it was reported that the organization of the human genome is closer to that of the chicken than the mouse. Thus, it is important to understand the central mechanism of feeding regulation in the neonatal chicks. In neuropeptides, the number of candidates as the orexigenic factor was less than those as the anorexigenic factor, even at an early growth stage. Some of the neuropeptides have reverse effects, e.g., ghrelin and prolactin releasing peptides, or no effects compared to the effects confirmed in mammals. Some of the genetic differences between meat-type (broiler) and layer-type chickens would explain the difference in food intake. On the other hand, it was difficult to explain the feeding mechanism by neuropeptides alone, as neonatal chicks have a repeated feeding, sleeping, and resting behavior within a short period. Some of the amino acids and their metabolites act centrally to regulate feeding with sedative and hypnotic effects. In conclusion, endogenous neuropeptides and endogenous and/or exogenous nutrients like amino acids collaborate to regulate feeding behavior in neonatal chicks.
... 26,47 The long feathers on the hindlimbs suggest that Microraptor was not a fastrunning terrestrial dinosaur, 62 because such long feathers likely provided resistance to fast running, in contradiction to the cursorial hypothesis for the origin of flight. 63,64 As in modern birds, the flight feathers of Microraptor were rooted deeply in the soft tissue of the animal with their very base touching or articulating with the wing bones. 65 The manual and pedal claws of Microraptor were elongated, curved and had pointed tip, resembling those in extant climbing animals (woodpeckers) and perching birds. ...
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Bionic design of flying robots based on natural models has become a hot topic in mechanical engineering. The research going on in this direction considers that there is a lot to learn from flying animals such as birds, insects, and bats, from walking on the ground to getting enough power to be airborne. To get an efficient design of flying robots, we must better understand the origin of flight. This paper focuses on the review of avian flight and its possible application in the design of flying robots. Different hypotheses have been proposed to tackle the origin and evolution of avian flight from cursorial dinosaurs to modern birds, including the famous ground-up and tree-down theories. During the past decade, discoveries of feathered and winged dinosaurs from Liaoning, China, strongly supported the theory that birds originated from theropod dinosaurs. The transition from running on the ground to maneuver in the sky involves various stages of flights and plumages, which can be now illustrated by several representative paravian dinosaurs from Liaoning. Those fossils provide good research bases for the design of flying robots. Microraptor is one of those important transitional stages in the evolution of flight. This paravian dinosaur is characterized by the presence of pennaceous feathers along both its arms and its legs, but how it could actually fly is still debated. It is of course difficult to evaluate the flight performances of an extinct animal, but aerodynamics of a four-wing robot can be developed to get some knowledge about its flying capacity. Fossil and living flying animals with different morphologies, stability, and control mechanism can be a source of inspiration for designing socially relevant products.
... The five mass extinctions in earth's history had major impacts on biodiversity, reshaping entire ecosystems and resulting in dramatic changes in the diversity of major clades [1][2][3][4] . The latest of these biotic crises, the Cretaceous -Paleogene (K-Pg) boundary 66 million years ago (MYA) 5 , is well known due to the extinction of non-avian dinosaurs 6,7 . There is a growing body of evidence that the composition of contemporary biodiversity has been significantly shaped by this last mass extinction event. ...
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Historical mass extinction events had major impacts on biodiversity patterns. The most recent and intensively studied event is the Cretaceous – Paleogene (K-Pg) boundary (ca. 66 million years ago [MYA]). However, the factors that may have impacted diversification dynamics vary across lineages. We investigated the macroevolutionary dynamics with a specific focus on the impact of major historical events such as the K-Pg mass extinction event on two major subclasses – Lecanoromycetidae and Ostropomycetidae – of lichen-forming fungi and tested whether variation in the rate of diversification can be associated with the evolution of a specific trait state - macrolichen. Our results reveal accelerated diversification events in three families of morphologically complex lichen-forming fungi – Cladoniaceae, Parmeliaceae, and Peltigeraceae – which are from the subclass Lecanoromycetidae and mostly composed of macrolichens, those that form three dimensional structures. Our RTT plot result for the subclass Lecanoromycetidae also reveals accelerated diversification. Changes in diversification rates occurred around the transition between Mesozoic and Cenozoic eras and was likely related to the K-Pg mass extinction event. The phylogenetic positions for rate increases estimated based on marginal shift probability are, however, scattered from 100 to 40 MYA preventing us from making explicit inference. Although we reveal that the phenotypic state of macrolichens is associated with a higher diversification rate than microlichens, we also show that the evolution of macrolichens predated the K-Pg event. Furthermore, the association between macrolichens and increased diversification is not universal and can be explained, in part, by phylogenetic relatedness. By investigating the macroevolutionary dynamics of lichen-forming fungi our study provides a new empirical system suitable to test the effect of major historical event on shaping biodiversity patterns and to investigate why changes in biodiversity patterns are not in concordance across clades. Our results imply that multiple historical events during the transition from Mesozoic to Cenozoic eras, including the K-Pg mass extinction event, impacted the evolutionary dynamics in lichen-forming fungi. However, future studies focusing on individual lichen-forming fungal families are required to ascertain whether diversification rates are associated with growth form and certain geological events.
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Global interspecific body size distributions have been suggested to be shaped by selection pressures arising from biotic and abiotic factors such as temperature, predation and parasitism. Here, we investigated the ecological and evolutionary drivers of global latitudinal size gradients in an old insect order. Global. Odonata (dragonflies and damselflies). We compiled data on interspecific variation in extant and extinct body sizes of Odonata, using an already existing database (The Odonate Phenotypic Database) and fossil data (The Paleobiology Database). We combined such body size data with latitudinal information and data on biotic and abiotic environmental variables across the globe to investigate and quantify interspecific latitudinal size‐gradients (“Bergmann's Rule”) and their environmental determinants. We used phylogenetic comparative methods and a global published phylogeny of Odonata to address these questions. Phylogenetic comparative analyses revealed that global size variation of extant Odonata taxa is negatively influenced by both regional avian diversity and temperature, with larger‐bodied species in the suborder Anisoptera (dragonflies) showing a steeper size‐latitude relationship than smaller‐bodied species in the suborder Zygoptera (damselflies). Interestingly, fossil data show that the relationship between wing size and latitude has shifted: latitudinal size trends had initially negative slopes but became shallower or positive following the evolutionary emergence and radiation of birds. The changing size‐latitude trends over geological and macroevolutionary time were likely driven by a combination of predation from birds and maybe pterosaurs and high dispersal ability of large dragonflies. Our study reveals that a simple version of Bergmann's Rule based on temperature alone is not sufficient to explain interspecific size‐latitude trends in Odonata. Our results instead suggest that latitudinal size gradients were shaped not only by temperature but also by avian predators, potentially driving the dispersal of large‐sized clades out of the tropics and into the temperate zone.
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The anatomy of the sternum in birds varies according to their habitats and type of locomotion. In particular, the carina sterni manifest different shape variations. In this study, the shape of the carina sterni was investigated by means of geometric morphometrics. Birds of different types of locomotion were used in the study: flying, swimming, and terrestrial. Ducks and chickens show a wider variety of shapes. Pigeons are the species with the least differences. The margo cranialis carinae in a turkey is the flattest compared to other species. In chickens, the apex carinae is more caudally than the base of the carina sterni. The margo cranialis of the carina sterni in ducks is concave. The differences in centroid size and shape differences between species collectively are statistically significant (p < 0.0001). The most distinct shape contrast is between the duck and turkey (p: 0.0003). Form differences between the ducks and geese as well as between the chicken and turkey are statistically insignificant. There is less variation in the shape of the carina sterni among avian species representing the same type of locomotion. Although there are many comparative morphological and morphometric studies of birds, shape analysis studies revealing the interspecific differences and similarities of the sternum are very limited. Morphology of the carina sterni can be useful in taxonomic investigations.
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The Frankfurt specimen of the early-branching ceratopsian dinosaur Psittacosaurus is remarkable for the exquisite preservation of squamous (scaly) skin and other soft tissues that cover almost its entire body. New observations under Laser-Stimulated Fluorescence (LSF) reveal the complexity of the squamous skin of Psittacosaurus, including several unique features and details of newly detected and previously-described integumentary structures. Variations in the scaly skin are found to be strongly regionalized in Psittacosaurus. For example, feature scales consist of truncated cone-shaped scales on the shoulder, but form a longitudinal row of quadrangular scales on the tail. Reexamined through LSF, the cloaca of Psittacosaurus has a longitudinal opening, or vent; a condition that it shares only with cro-codylians. This implies that the cloaca may have had crocodylian-like internal anatomy, including a single, ventrally-positioned copulatory organ. Combined with these new integu-mentary data, a comprehensive review of integument in ceratopsian dinosaurs reveals that scalation was generally conservative in ceratopsians and typically consisted of large subcircular-to-polygonal feature scales surrounded by a network of smaller non-overlapping polygonal basement scales. This study highlights the importance of combining exceptional specimens with modern imaging techniques, which are helping to redefine the perceived complexity of squamation in ceratopsians and other dinosaurs.
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From minute-to-minute changes, or across daily, seasonal, or geological timescales, animals are forced to navigate dynamic surroundings. Their abiotic environment is continually changing. These changes could include alterations to the substrates animals locomote on, flow dynamics of the microhabitats they feed in, or even altitudinal shifts over migration routes. The only constancy in any organism's day-to-day existence is the heterogeneity of the habitats they move through and the gradients in the physical media (e.g., air, water) they live in. We explored a broad range of organismal transitions across abiotic gradients and investigated how these organisms modify their form, function, and behavior to accommodate their surrounding media. We asked the following questions: (1) What are some challenges common to animals in changing media or moving between media? (2) What are common solutions to these recurring problems? (3) How often are these common solutions instances of either convergence or parallelism? Our symposium speakers explored these questions through critical analysis of numerous datasets spanning multiple taxa, timescales, and levels of analysis. After discussions with our speakers, we suggest that the role of physical principles (e.g., drag, gravity, buoyancy, viscosity) in constraining morphology and shaping the realized niche has been underappreciated. We recommend that investigations of these transitions and corresponding adaptations should include comparisons at multiple levels of biological organization and timescale. Relatedly, studies of organisms that undergo habitat and substrate changes over ontogeny would be worthwhile to include in comparisons. Future researchers should ideally complement lab-based morphological and kinematic studies with observational and experimental approaches in the field. Synthesis of the findings of our speakers across multiple study systems, timescales, and transitional habitats suggests that behavioral modification and exaptation of morphology play key roles in modulating novel transitions between substrates.
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The Frankfurt specimen of the early-branching ceratopsian dinosaur Psittacosaurus is remarkable for the exquisite preservation of squamous (scaly) skin and other soft tissues that cover almost its entire body. Newly detected details revealed under Laser-Stimulated Fluorescence (LSF) reveals the complexity of the squamous skin of Psittacosaurus , including several unique features and details of newly detected and previously-described integumentary structures. Variations in the scaly skin are found to be strongly regionalised in Psittacosaurus . For example, feature scales consist of truncated cone-shaped scales on the shoulder, but form a longitudinal row of quadrangular scales on the tail. Re-examined through LSF, the cloaca of Psittacosaurus has a longitudinal opening, or vent; a condition that it shares only with crocodylians. This implies that the cloaca had crocodylian-like internal anatomy, including a single, ventrally-positioned copulatory organ. Combined with these new integumentary data, a comprehensive review of integument in ceratopsian dinosaurs reveals that scalation was generally conservative in ceratopsians and typically consisted of large subcircular-to-polygonal feature scales surrounded by a network of smaller non-overlapping polygonal basement scales. This study highlights the importance of combining exceptional specimens with modern imaging techniques, which are helping to redefine the perceived complexity of squamation in ceratopsians and other dinosaurs.
Chapter
Many readers will be acquainted with phylogenetic terminology and avian osteology, and it is beyond the scope of the present work to provide an in-depth overview of these topics, each of which could fill a book on its own. For those less familiar with essential terms and definitions, these are outlined in the present chapter, which also introduces major features of the skull and some of the limb and pectoral girdle bones. Current hypotheses on the interrelationships of extant birds are reviewed, which constitute a phylogenetic framework for the study of fossil taxa. In order to set the following chapters on Paleogene birds into a full context, the Mesozoic fossil record of neornithine birds is furthermore discussed and an overview is given of major Paleogene fossil localities.
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Genomic data are important for understanding the origin and evolution of traits. Under the context of rapidly developing sequencing technologies and more widely available genome sequences, researchers are able to study evolutionary mechanisms of traits via comparative genomic methods. Compared with other vertebrates, bird genomes are relatively small and exhibit conserved synteny with few repetitive elements, which makes them suitable for evolutionary studies. Increasing genomic progress has been reported on the evolution of powered flight, body size variation, beak morphology, plumage coloration, high-elevation colonization, migration, and vocalization. By summarizing previous studies, we demonstrate the genetic bases of trait evolution, highlighting the roles of small-scale sequence variation, genomic structural variation, and changes in gene interaction networks. We suggest that future studies should focus on improving the quality of reference genomes, exploring the evolution of regulatory elements and networks, and combining genomic data with morphological, ecological, behavioral, and developmental biology data.
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Birds are living dinosaurs, an evolutionary transition increasingly well documented in the abundant fossil record of Mesozoic birds. The avian fossil record begins 150 Ma (million years ago) in the late Jurassic, and for the next 85 million years, birds experienced an evolutionary radiation resulting in a wide range of body forms and lifestyles, occupying all continents and many different environments. This Mesozoic radiation culminated in the appearance of modern birds, Neornithes, in the late Cretaceous, and the loss of several archaic groups during the mass extinction event at the end of this period. Key Concepts • Birds evolved from maniraptoran theropod dinosaurs during the middle of the Mesozoic Era, over 150 Ma (million years ago). • Many unique adaptations of modern birds, from flight feathers to coloured eggs, evolved amongst their dinosaurian predecessors. • A broad diversity of pre‐modern birds lived during the Cretaceous Period, their fossil record is well known from about 131 to 66 Ma. • The Mesozoic radiation of pre‐modern birds paralleled many aspects of the biology of their living counterparts. • Neornithes, or modern birds, originated in the late Cretaceous, were the only group of birds to survive the extinction event at the end of this period, and went on to diversify into the abundant forms seen today.
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Jianianhualong tengi is a key taxon for understanding the evolution of pennaceous feathers as well as troodontid theropods, and it is known by only the holotype, which was recovered from the Lower Cretaceous Yixian Formation of western Liaoning, China. Here, we carried out a large-area micro-X-Ray fluorescence (micro-XRF) analysis on the holotypic specimen of Jianianhualong tengi via a Brucker M6 Jetstream mobile XRF scanner. The elemental distribution measurements of the specimen show an enrichment of typical bones couponing elements such as S, P and Ca allowing to visualize the fossil structure. Additionally, to this, the bones are enriched in several heavier elements such as Sr, Th, Y and Ce over the surrounding rocks. The enrichment is most likely associated to secondary mineralization and the phosphates from the bones. Interestingly the plumage shape correlates with an enrichment in elements such as Cu, Ni and Ti, consistent with a previous study [1] on Archaeopteryx using synchrotron imaging. The analysis presented here provide new biological and taphonomic information of this fossil. An in-situ and nondestructive micro-XRF analysis is currently the most ideal way to map the chemistry of fossils, so far this is manly restricted to small samples. Larger samples usually required a synchrotron facility for analysis. Our study demonstrated that laboratory-based large-area micro-XRF scanner can provides a practical tool for the study of large large-sized specimens allowing collect full chemical data for a better understanding of evolutionary and taphonomic processes.
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The avian transition from long to short, distally fused tails during the Mesozoic ushered in the Pygostylian group, which includes modern birds. The avian tail embodies a bipartite anatomy, with the proximal separate caudal vertebrae region, and the distal pygostyle, formed by vertebral fusion. This study investigates developmental features of the two tail domains in different bird groups, and analyzes them in reference to evolutionary origins. We first defined the early developmental boundary between the two tail halves in the chicken, then followed major developmental structures from early embryo to post-hatching stages. Differences between regions were observed in sclerotome anterior/posterior polarity and peripheral nervous system development, and these were consistent in other neognathous birds. However, in the paleognathous emu, the neognathous pattern was not observed, such that spinal nerve development extends through the pygostyle region. Disparities between the neognaths and paleognaths studied were also reflected in the morphology of their pygostyles. The ancestral long-tailed spinal nerve configuration was hypothesized from brown anole and alligator, which unexpectedly more resembles the neognathous birds. This study shows that tail anatomy is not universal in avians, and suggests several possible scenarios regarding bird evolution, including an independent paleognathous long-tailed ancestor.
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Non‐avian theropods were a highly successful clade of bipedal, predominantly carnivorous, dinosaurs. Their diversity and macroevolutionary patterns have been the subject of many studies. Changes in fossil specimen completeness through time and space can bias our understanding of macroevolution. Here, we quantify the completeness of 455 non‐avian theropod species using the skeletal completeness metric (SCM), which calculates the proportion of a complete skeleton preserved for a specimen. Temporal patterns of theropod skeletal completeness show peaks in the Carnian, Oxfordian–Kimmeridgian and Barremian–Aptian, and lows in the Berriasian and Hauterivian. Lagerstätten primarily drive the peaks in completeness and observed taxonomic diversity in the Oxfordian–Kimmeridgian and the Barremian–Aptian. Theropods have a significantly lower distribution of completeness scores than contemporary sauropodomorph dinosaurs but change in completeness through time for the two groups shows a significant correlation when conservation Lagerstätten are excluded, possibly indicating that both records are primarily driven by geology and sampling availability. Our results reveal relatively weak temporal sampling biases acting on the theropod record but relatively strong spatial and environmental biases. Asia has a significantly more complete record than any other continent, the mid northern latitudes have the highest abundance of finds, and most complete theropod skeletons come from lacustrine and aeolian environments. We suggest that these patterns result from historical research focus, modern climate dynamics, and depositional transportation energy plus association with conservation Lagerstätten, respectively. Furthermore, we find possible ecological biases acting on different theropod subgroups, but body size does not influence theropod completeness on a global scale.
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Phylogenetic taxonomy, that component of phylogenetic systematics concerned with the verbal representation (rather than the reconstruction or estimation) of phylogenetic relationships, was developed by de Queiroz and Gauthier (1990, 1992, 1994). Under phylogenetic taxonomy, all taxon names are names of clades (i.e., an ancestor and all of that ancestor's descendants). De Queiroz and Gauthier (1990, 1992, 1994) described three possible ways of denning clade names within the phylogenetic taxonomic system: 1) node-based definitions (Figure 1.1), of the form “the most recent common ancestor of Taxon A and Taxon B, and all of that ancestor's descendants”; 2) stem-based definitions (Figure 1.2), of the form “Taxon A and all taxa sharing a more recent common ancestor with Taxon A than with Taxon B”; and 3) apomorphy-based definitions (Figure 1.3), of the form “the first taxon with derived character X and all of that ancestor's descendants.” Bryant (1994) noted that, while the first two definition types will always be stable, apomorphy-based definitions are potentially confusing if that derived character is found to occur in more than one lineage (i.e., is homoplastic). Under the phylogenetic system of taxonomy, definitions of taxon names are independent with respect to previous diagnosis (as particular character states may be found to occur in other lineages or in more inclusive clades) and composition (as particular member taxa may subsequently be found to lie outside the defined clade boundary). This paper is the initial work in an ongoing study by Holtz and Padian (1995, in preparation) to clarify the phylogenetic taxonomy of major clades of theropods and related taxa.
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Cretaceous birds and avian phylogeny Andrzej Elzanowski Courier Forschungsinstitut Senckenberg 181 (1995): 37-53. The paper is the first attempt to redefine in terms of skeletal evidence the major avian lineages (Ornithurae, Carinatae, Enantiornithes, Neornithes) following the recent discoveries of many Mesozoic birds. An enantiornithine specimen MUCPv-142 from the Rio Colorado Formation, Argentina (Chaippe 1991) reveals a temporal pattern of ossification that is very similar to that described in Gobipteryx (Elzanowski 1981) and confirms that Enantiornithes were superprecocial. The published descriptions of Gobipteryx are supplemented by partial reconstructions of the coracoid and bony palate. The coracoid is strikingly similar to that described by Walker (1981). The bony palate shows a large primary choanal fenestra located rostrally to the palatines, and a small subsidiary palatal fenestra behind, as in the theropods. The neornithine choana seems to have moved to the subsidiary fenestra. The Cretaceous record of Neornithes is briefly reviewed with the emphasis on the confusion that surrounds Ichthyornis and Apatornis as described by Marsh (1880), and Baptornis as described by Martin and Tate (1976). Cranial morphology of the Mesozoic birds provides the plesiomorphic background for the analysis of palaeognathous and neognathous characters. A one-piece pterygoid turns out to be another palaeognathous synapomorphy and all cranial evidence consistently shows a dichotomy between Struthio and non-struthioniform palaeognaths, thus precluding the tinamous from being the first branch of crown palaeognaths.
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The skull of Hesperonis proves to be neognathous in the majority of diagnostic characters including the presence of the intrapterygoid joint. Most of the remaining characters, including those shared with the paleognaths, are primitive for Neornithes or all birds. In details of the braincase structure, Hesperornis is most similar to Enaliornis, Procellariiformes, Phaethon, and Fregata. A new reconstruction of the palate predicts the presence of the lacrimopalatine (uncinate) and vomer.
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Skulls of Gobipteryx (Aves) from the Upper Cretaceous of Mongolia Andrzej Elzanowski Palaeontologia Polonica 37 (1977), 153-165 Following a preliminary report (Elzanowski 1974), the holotype skull of Gobipteryx minuta is redescribed and another cranial specimen described for the first time. The second specimen confirms the palaeognathous pattern of the palate and (upper) jaw as reconstructed from the poorly preserved palate of the holotype specimen. The avian identity of Gobipteryx is reaffirmed despite claims to the contrary (Brokorb 1976).
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Seven perinatal specimens of Gobipteryx, including two incomplete skeletons and five smaller fragments, reveal a unique combination of characters some of which have been unknown in birds. Most of these specimens were found with eggshell fragments which faced the bones by their concave (inner) surfaces. In both skeletons the neck turns under the body and the skull is directed straight to the back, resulting in the head-between-legs position as in today’s Megapodiidae. In contrast to other body regions, the thoracic vertebrae, shoulder girdle, and wing skeleton are almost completely ossified, and the latter exceeds in relative length all modern birds except for the Megapodiidae. This reveals a flight apparatus that was ready for use upon hatching, and thus a superprecocial mode of development in Gobipteryx. Two cervicodorsal vertebrae have their spinal processes fused into a nuchal blade which may have helped in underground hatching by wriggling the shoulders as described in the Megapodiidae. The nuchal blade may also have strengthened the flight apparatus.
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Tyrannosaurids are a well-supported clade of very large predatory dinosaurs of Late Cretaceous Asiamerica. Traditional dinosaurian systematics place these animals within the infraorder Carnosauria with the other large theropods (allosaurids, megalosaurids). A new cladistic analysis indicates that the tyrannosaurs were in fact derived members of the Coelurosauria, a group of otherwise small theropods. Despite certain gross cranial similarities with the large predators of the Jurassic and Early Cretaceous, the Late Cretaceous tyrannosaurids are shown to be the sister group to ornithomimids and troodontids, which share a derived condition of the metatarsus. This clade is found to be nested within Maniraptora, which is a more inclusive taxon than previously recognized. The atrophied carpal structure found in tyrannosaurids and ornithomimids is derived from a maniraptoran condition with a large semilunate carpal, rather than from the plesiomorphic theropod morphology. The taxa “Carnosauria” and “Deinonychosauria” (Dromaeosauridae plus Troodontidae) are shown to be polyphyletic, and the Late Jurassic African form Elaphrosaurus is found to be the sister taxon to Abelisauridae rather than a primitive ornithomimosaur. Purported allosaurid-tyrannosaurid synapomorphies are seen to be largely size-related, present in the larger members of both clades, but absent in smaller members of the Tyrannosauridae. The remaining giant tetanurine theropods (Megalosaurus and Torvosaurus) were found to be progressively distant outgroups to an allosaurid-coelurosaur clade. The inclusion of the Tyrannosauridae within Maniraptora suggests a major adaptive radiation of coelurosaurs within Cretaceous Asiamerica comparable to contemporaneous radiations in various herbivorous dinosaurian clades.
Chapter
First published in 1983 to celebrate the centennial of the American Ornithologists' Union, Perspectives in Ornithology collects together a series of essays and commentaries by leading authorities about especially active areas of research on the biology of birds. Readers will find in this collection a useful overview of many major concepts and controversies in ornithology.
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Discusses the nature of Archaeopteryx with particular reference to bipedalism and flight, and reviews hypotheses on the origin of birds: pseudosuchian origin, ornithischian relationship, crocodilian relationship, and coelurosaurian origin. Concerning the origin of flight, it is probable that feathers originally evolved for their aerodynamic qualities, and that use of feathers for thermoregulation postdated the development of powered flight. Fully-improved bipedal posture appeared relatively late in avian evolution, perhaps not before the Cretaceous. Avian flight is unlikely to have originated in a cursorial-terrestrial biped. Bipedality in birds may originally have been for arboreal leaping rather than for fast running.-P.J.Jarvis
Article
The evolution of avian flight can be interpreted by analyzing the sequence of modifications of the primitive tetrapod locomotor system through time. Herein, we introduce the term "locomotor module" to identify anatomical subregions of the musculoskeletal system that are highly integrated and act as functional units during locomotion. The first tetrapods, which employed lateral undulations of the entire body and appendages, had one large locomotor module. Basal dinosaurs and theropods were bipedal and possessed a smaller locomotor module consisting of the hind limb and tail. Bird flight evolved as the superimposition of a second (aerial) locomotor capability onto the ancestral (terrestrial) theropod body plan. Although the origin of the wing module was the primary innovation, alterations in the terrestrial system were also significant. We propose that the primitive theropod locomotor module was functionally and anatomically subdivided into separate pelvic and caudal locomotor modules. This decoupling freed the tail to attain a new and intimate affiliation with the forelimb during flight, a configuration unique to birds. Thus, the evolution of flight can be viewed as the origin and novel association of locomotor modules. Differential elaboration of these modules in various lineages has produced the diverse locomotor abilities of modern birds.
Article
Current scenarios frequently interpret the Late Jurassic bird Archaeopteryx as having had an avian-type physiology and as having been capable of flapping flight, but only from "the trees downward." It putatively lacked capacity for takeoff and powered flight from the ground upward. Data from extant reptiles indicate that if Archaeopteryx were physiologically reptilian, it would have been capable of ground upward takeoff from a standstill, as well as "trees downward" powered flight. This conclusion is based largely on a previously unrecognized attribute of locomotory (skeletal) muscle in a variety of extant reptiles: During "burst-level" activity, major locomotory muscles of a number of active terrestrial taxa generate at least twice the power (watts kg(-1) muscle tissue) as those of birds and mammals. Reptilian physiological status also helps resolve the apparently uneven development of various flight support structures in Archaeopteryx (e.g., well-developed flight features but relatively unspecialized pectoral girdle, supracoracoideus muscles, etc.). Endothermy and capacity for longer-distance powered flight probably evolved only in Early Cretaceous birds, which were the first birds to have a keeled sternum, strap-like coracoid, and hypocleidium-bearing furcula.
Article
Recent discoveries have resulted in a great deal of new data that prompt revision of hypotheses for the origin of birds and the first steps in their evolution. They favour the concept that birds originated from among the Theropods. Further, the finding of a Triassic bird in Texas (Protoavis) and a bird from the Upper Cretaceous of Mongolia (Mononykus) suggests two scenarios for the evolution of flight: (1) flight ability lost in the mononykosaur lineage; (2) two periods when flight appeared in birds. -Author
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This new Triassic reptile, is reported from the Norian dolostones and dolomitic bituminous limestones of the Preone valley (Ampezzo, Province of Udine, Italy). -from Authors
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Concornis lacustris gen. et sp. nov. is a new fossil bird from the Early Cretaceus (Barremian) of Las Hoyas, Cuenca, Spain. Concornis is roughly twice the size of Iberomesornis, the first bird described from Las Youas, but it is not the adult of the latter. Concornis is more derived than Iberomesornis, with a true tibiotarsus and a fan-like distal metatarsal zone with distinct trochlear structures. Concornis is one of the closer known sister taxa of the Ornithurae. This sister group plus Iberomesornis form the clade Euornithes, diagnosed by a strut-like coracoid, a derived avian furcula and a pygostyle. There is increasing evidence for an adaptive radiation of birds during the Early Cretaceous. After feathers appeared, the first stage of the radiation was the rapid evolution of active flight structures. Based on a "legginess index' in extant birds, an aquatic habit is suggested for Las Hoyas birds. -from Authors
Article
The origin of flight can be approached through a combination of phylogenetic, functional, and aerodynamic evidence. A basic question is whether flight evolved in the trees or on the ground. Of the three groups of active flyers, two (pterosaurs and birds) show no trace of gliding antecedents and appear to have evolved flight directly from the ground. Bats show many morphological and phylogenetic indications of an arboreal, gliding ancestry and are very different in all such respects from pterosaurs and birds. Pterosaurs were structurally and functionally convergent on birds in many locomotory respects, and show prima-facie evidence of a cursorial, non-gliding origin of flight. Aerodynamic considerations of extinct vertebrates have mainly focused on two animals: Archaeopteryx (the first known bird) and Pteranodon (a specialized Cretaceous pterosaur). Functional inferences from skeletal evidence imply that Archaeopteryx was capable of flapping flight, though most 'modern' avian flight features were not developed; it does not seem well built for gliding. Pteranodon (a soarer, not a glider), like many large birds was capable of active flight but probably only used it to take off, gain altitude, and avert danger. All pterosaurs were strong, active fliers and only large size constrained this ability. Reappraisal of the anatomy and aerodynamic parameters indicate that Pteranodon's flight range was higher and that it was more active and manoeuverable than previous studies have suggested, and so more comparable to modern soaring birds. Studies of flight in extinct organisms cannot rely solely on engineering models or presumed selective advantages or pressures; they must take into consideration all aspects of phylogeny, function, and aerodynamics.from Author
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This chapter documents survivorship across the Cretaceous/Tertiary (K/T) (and Lancian/Puercan) boundary for all 111 species of nonmarine vertebrates from Garfield and McCone counties, Montana. Species-level survivorship appears to be between about 53 and 64 percent after the artifacts caused by paleobiogeography, rarity of some species, and differing evolutionary rates are taken into account. Without correcting for these artifacts, survival is an artificially low 32 percent. If specimens from the Bug Creek interval are early Paleocene (Puercan) in age, survivorship is an almost certainly incorrectly high value of 82 percent. This is because an undetermined number of latest Cretaceous (Lancian) species in the Bug Creek interval probably were reworked from Cretaceous sediments and were extinct by Bug Creek time. Comparison of the Lancian/ Puercan transition with the older Judithian/Lancian and younger Puercan/Torrejonian transitions suggests percentage survival is similar among the three (55, 48, and 58 percent, respectively) after the Lazarus effect is considered. These results are not easily explained by a catastrophic mass-extinction scenario for the K/T transition, at least for nonmarine vertebrates. Rather, a geologically rapid but noncatastrophic change, such as the loss of range and habitat diversity during the Late Cretaceous marine regression, is commensurate with the analysis.
Article
The concavoconvex glenoid and bulbous humeral head of modern birds represent both structurally and functionally a hemisellar (half saddle) joint modified from a pattern common among post-Paleozoic tetrapods. Birds share with crocodilians, their nearest living relatives, similarities in joint architecture, including scapulohumeral and coracohumeral ligaments. The glenoid underwent a major reorientation during the evolution of the avian shoulder from the primitive condition of being posteroventrally directed as in Deinonychus antirrhopus and coelurosaurs generally to being dorsolaterally directed as in modern forms. The laterally facing glenoid of Archaeopteryx lithographica was intermediate in orientation and provided for a substantial degree of wing elevation but not the fully abducted, sagittal positioning that modern birds employ at the upstroke-downstroke transition. -Author
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One of the most important avian fossils is a nearly complete skeleton of a hesperornithid from the late Cretaceous Niobrara Chalk Formation of western Kansas found by H. T. Martin in 1894. Williston assigned it to Hesperornis gracilis, a form named by Marsh but never really diagnosed or illustrated. Because of the size and apparent completeness of Marsh's monumental work on the Mesozoic birds of North America, these birds have been largely ignored since its publication. This has largely been the fate of H. T. Martin's exceptional specimen, parts of which have been figured under both Hesperornis gracilis, and H. regalis. This specimen can now be shown to be a previously undescribed genus of hesperornithiform bird, that provides the basis for a re-evaluation of the relationships of the Hesperornithiformes to other Mesozoic birds. Archaeopteryx is a member of a side-branch of avian evolution, the subclass Sauriurae, which became extinct at the end of the Mesozoic. The hesperornithiform Enaliornis is the earliest bird which can be shown to belong to the subclass Ornithurae to which all modern birds belong.
Article
Numerical cladistic analysis of 73 cranial and postcranial characters has resulted in a highly corroborated hypothesis describing the phylogenetic pattern of early avian evolution. Using “non-avian theropod” dinosaurs as a comparative outgroup and root for the tree, the analysis confirmed Archaeopteryx to be the sister-group of all remaining avian taxa, or Ornithurae. This latter taxon is subdivided into two lineages, the Hesperornithiformes and the Carinatae. The carinates, in turn, were also resolved into two sister-groups, the Ichthyornithiformes and the modern birds, or Neornithes. This paper provides morphological data corroborating the divergence of the two basal clades of the Neornithes: the Palaeognathae (tinamous and ratites) and Neognathae (all other modern birds). The phylogenetic relationships of four important Cretaceous taxa were also investigated, but these fossil taxa were too fragmentary to determine their phylogenetic position unambiguously. Alexornis and Ambiortus are both carinates, but their relationships cannot be resolved in greater detail. The relationships of the Enantiornithes may lie within the Carinatae or these two taxa may be sister-groups. Gobipteryx is a neornithine and possibly the sister-group of the Palaeognathae. This analysis indicates that major patterns of morphological change took place at the time of origin of the ancestors of the Ornithurae and the Carinatae. Ornithurine innovations included major changes throughout the skeleton, whereas those of the carinates, while substantial, were primarily restricted to the pectoral girdle and forelimb. The phylogenetic results, in conjunction with the known ages of fossil taxa, indicate that the early lineages of birds very likely arose in the Jurassic. The early cladistic events within the neornithine lineage are also more ancient than generally recognized, and may well extend back to the early Cretaceous.
Article
Small vertebrates were recovered from the matrix encasing specimens of giant sauropod dinosaurs (Supersaurus, Ultrasaurus, Dystylosaurus) collected from the "Dry Mesa' Quarry (Brushy Basin Member, Morrison Formation, western Colorado). Most of the remains appear to pertain to a single form of pterodactyloid pterosaur, Mesadactylus ornithosphyos, n.gen. and sp. the holotype of which is a synsacrum. A bone end from this quarry, first identified as an avian proximal tibia and named Palaeopteryx thomsoni, is reidentified as the distal radius of a small deinonychosaur or bird. A small femur of a small deinonychosaur or bird and additional material of other small vertebrates from this quarry are figured and described. -Authors