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A new genus and species of Late Cretaceous (Coniancian–Santonian) birds, Neuquenornis volans, is described. This new taxon is known from a fairly complete, articulated specimen from the Río Colorado Formation of northwestern Patagonia. Synapomorphies of the humerus, radius, ulna, coracoid, femur, tibiotarsus, tarsometatarsus, and thoracic vertebrae, support its allocation to the Enantiornithes. The tarsometatarsal structure of Neuquenornis refers it to the Late Cretaceous family Avisauridae. The structure of the wing and pectoral girdle of Neuquenornis indicates that it was an active flyer, an aptitude also inferred for the El Brete enantiornithines from the Upper Cretaceous Lecho Formation of northwestern Argentina. The pedal structure of Neuquenornis and Soroavisaurus from El Brete, indicates that avisaurids were capable of perching in trees.
... Although Late Cretaceous enantiornithines have been collected from nearly every continent except for Antarctica, specimens are far fewer and typically very fragmentary. Very few articulated specimens are known (only Neuquenornis, Parvavis and Elsornis) (Chiappe & Calvo, 1994;Chiappe et al. 2006;Wang et al. 2014) and the only notable cranial material is that of Gobipteryx from Mongolia (Elzanowski, 1976;Chiappe et al. 2001), Neuquenornis from Argentina (Chiappe, 1996) and the recently described Falcatakely from the uppermost Cretaceous deposits of Madagascar . In contrast to Early Cretaceous specimens, Late Cretaceous enantiornithines are more commonly preserved in three dimensions (Chiappe & Calvo, 1994;Elzanowski, 1976;Chiappe et al. 2001;Atterholt et al. 2018). ...
... Very few articulated specimens are known (only Neuquenornis, Parvavis and Elsornis) (Chiappe & Calvo, 1994;Chiappe et al. 2006;Wang et al. 2014) and the only notable cranial material is that of Gobipteryx from Mongolia (Elzanowski, 1976;Chiappe et al. 2001), Neuquenornis from Argentina (Chiappe, 1996) and the recently described Falcatakely from the uppermost Cretaceous deposits of Madagascar . In contrast to Early Cretaceous specimens, Late Cretaceous enantiornithines are more commonly preserved in three dimensions (Chiappe & Calvo, 1994;Elzanowski, 1976;Chiappe et al. 2001;Atterholt et al. 2018). These preservational biases hinder comparison between Early and Late Cretaceous species and obfuscate attempts to understand evolutionary trajectories during the 65 million years of enantiornithine evolution. ...
... The most complete Late Cretaceous skeleton to date is the holotype and only known specimen of Neuquenornis volans from the Santonian Bajo de la Carpa Formation in Argentina, which preserves only the neurocranium of the skull (Chiappe & Calvo, 1994). The only other Late Cretaceous enantiornithine from China is a partial skeleton of a young enantiornithine, the holotype of Parvavis chuxiongensis, from the lacustrine Upper Cretaceous (Turonian-Santonian) deposits in Yunnan Province, southern China (Wang et al. 2014). ...
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A new enantiornithine bird is described on the basis of a well preserved partial skeleton from the Upper Cretaceous Qiupa Formation of Henan Province (central China). It provides new evidence about the osteology of Late Cretaceous enantiornithines, which are mainly known from isolated bones; in contrast, Early Cretaceous forms are often represented by complete skeletons. While the postcranial skeleton shows the usual distinctive characters of enantiornithines, the skull displays several features, including confluence of the antorbital fenestra and the orbit and loss of the postorbital, evolved convergently with modern birds. Although some enantiornithines retained primitive cranial morphologies into the latest Cretaceous Period, at least one lineage evolved cranial modifications that parallel those in modern birds.
... sutures) among the osteological components, similar to other adult or subadult enantiornithine specimens [28], suggesting that MPM-334-1 was skeletally mature (electronic supplementary material, figure S1; figure 1). The foramen magnum is subquadrangular, with a gently concave dorsal margin, and is much larger than the round occipital condyle, resembling the condition in the enantiornithine Neuquenornis [29] but unlike Yuornis [9] or Zhouornis in which these structures are more similar in size (electronic supplementary material, figure S1; figure 1). The orientation of the foramen magnum is nearly 60 degrees when the parasphenoid rostrum is oriented horizontally (the internal angle between the transverse plane of the foramen magnum and the longitudinal axis of the parasphenoid rostrum is 124.1 degrees; see Methods), indicating a substantial degree of braincase rotation (figure 1). ...
... B 289: 20221398 ventrolaterally projecting paraoccipital process (electronic supplementary material, figure S1; figure 1). The exit of a cranial nerve identified as the XII (hypoglossal, two exits as in Neuquenornis [29]) is visible, ventrally, on either side of the occipital condyle, which is also lateroventrally flanked by paired excavations (one on top of the other). Within the dorsally positioned excavation, preserved only on the right side, is an additional foramen, which we identify as the exit of a bundle of nerves including cranial nerves IX-XI (glossopharyngeal, vagus and accessory nerves) (figures 1 and 2). ...
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Among terrestrial vertebrates, only crown birds (Neornithes) rival mammals in terms of relative brain size and behavioural complexity. Relatedly, the anatomy of the avian central nervous system and associated sensory structures, such as the vestibular system of the inner ear, are highly modified with respect to those of other extant reptile lineages. However, a dearth of three-dimensional Mesozoic fossils has limited our knowledge of the origins of the distinctive endocranial structures of crown birds. Traits such as an expanded, flexed brain, a ventral connection between the brain and spinal column, and a modified vestibular system have been regarded as exclusive to Neornithes. Here, we demonstrate all of these 'advanced' traits in an undistorted braincase from an Upper Cretaceous enantiornithine bonebed in southeastern Brazil. Our discovery suggests that these crown bird-like endocranial traits may have originated prior to the split between Enantior-nithes and the more crownward portion of avian phylogeny over 140 Ma, while coexisting with a remarkably plesiomorphic cranial base and posterior palate region. Altogether, our results support the interpretation that the distinctive endocranial morphologies of crown birds and their Mesozoic relatives are affected by complex trade-offs between spatial constraints during development.
... Whether or not all of these species are valid rarely been rigorously examined. For example, debate over the synonymy of C altus [67], Hesperornis altus [64], and Hesperornis montana [64] has appeared in the li with both Coniornis and H. montana being invalidated without H. altus ever being in the form of a concise diagnostic description and justification of the "valid" tax The examples of fraught taxonomy of hesperornithiforms described here illustrate opportunities for future research, as significant synthesis and revision may be achieved from broad-scale studies of currently known material, enhanced and improved with the addition of more recently discovered material that has not been previously published as well as future discoveries [65]. ...
... The explosion of Mesozoic bird fossils in the 1990s from China, South America, and Europe initiated a new wave of research into early bird evolution, including the widespread application of modern phylogenetic methods. In these analyses, hesperornithiforms, usually represented by Hesperornis, consistently placed as fairly derived within Ornithuromorpha, usually as the sister taxon to a clade containing Ichthyornis and modern birds (e.g., [32,[66][67][68]). More recent work involving multiple hesperornithiform taxa has returned the Hesperornithiformes as the sister taxon to Neornithes, or crown clade birds [22,[69][70][71], while other studies retain the placement of the hesperornithiforms as sister to Ichthyornis + Neornithes [24,72,73]. ...
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The Hesperornithiformes (sometimes referred to as Hesperornithes) are the first known birds to have adapted to a fully aquatic lifestyle, appearing in the fossil record as flightless, foot-propelled divers in the early Late Cretaceous. Their known fossil record—broadly distributed across the Northern Hemisphere—shows a relatively rapid diversification into a wide range of body sizes and degrees of adaptation to the water, from the small Enaliornis and Pasquiaornis with lesser degrees of diving specialization to the large Hesperornis with extreme morphological specializations. Paleontologists have been studying these birds for over 150 years, dating back to the “Bone Wars” between Marsh and Cope, and as such have a long history of naming, and renaming, taxa. More recent work has focused to varying degrees on the evolutionary relationships, functional morphology, and histology of the group, but there are many opportunities remaining for better understanding these birds. Broad-scale taxonomic evaluations of the more than 20 known species, additional histological work, and the incorporation of digital visualization tools such as computed tomography scans can all add significantly to our understanding of these birds.
... In addition to the aforementioned plesiomorphic features, K. mater also shares with Enantiornithes a proportionally narrow shaft and small trochlea of metatarsal IV (also shared with confuciusornithids and the basal ornithuromorph Khinganornis hulunbuirensis Wang, Cau, Kundrát, Chiappe, Ji, Wang, Li and Wu, 2020;O'Connor et al., 2014), distally expanded metatarsal II trochlea with respect to metatarsal shaft (in K. mater this trochlea is smaller than that of metatarsal III, whereas in most Enantiornithes and confuciusornithids the trochlea of metatarsal II is wider than that of metatarsal III; Sereno, 2000;O'Connor et al., 2014), and proportionally large ungual phalanges (Chiappe and Calvo, 1994;Sereno, 2000;Zhang et al., 2001;Wang et al., 2014;Fig. 6). ...
... In K. mater the only available ungual phalanx (presumably corresponding to digit II) is proportionally stout and distally hooked, with relatively large flexor tubercles (in Enantiornithes, well-developed flexor tubercles are not present; e.g., Chiappe, 1993;Chiappe and Calvo, 1994;Kurochkin, 1995;Sanz et al., 2002;Carvalho et al., 2015a, b). The ungual morphology of K. mater strongly differs from that of other Early Cretaceous ornithuromorphs (e.g., Archaeorhynchus spathula, Gansus yumenensis, Songlingornithidae, Hongshanornithidae, Schizoouridae; Hou and Liu, 1984;Hou, 1997;You et al., 2006;Zhou and Zhang, 2006;, which show small and dorsoplantarly short ungual phalanges. ...
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The fossil record of Early Cretaceous birds in South America has been restricted to members of Enantiornithes from the Crato Formation (Aptian) of Brazil. Here we describe a new genus and species of bird discovered at Pedra Branca Mine, Nova Olinda County, Ceará State, Brazil, which adds to the avian fossil record from the Crato Formation. The specimen is represented by an isolated foot that is exposed in plantar view. A plantarly displaced metatarsal III with a well-developed hypotarsus supports its referral to Ornithuromorpha, representing the oldest member of the clade reported for Gondwana. Its unique foot conformation indicates that it may belong to an unknown ornithuromorph clade with some cursory similarities to extant flightless ratites. The presence of Early Cretaceous ornithuromorphs in Brazil indicates that the clade was widespread in Gondwana during the Mesozoic. http://zoobank.org/urn:lsid:zoobank.org:pub:08333BA3-F231-4E61-9E89-105C7478AE31
... Furthermore, the stronger curvature of MPM-PV-22867, may indicate that it belongs to the hallux. Ungual phalanges are referred to enantiornithine birds by virtue of having poorly developed flexor tubercles, a ventral "V" shaped groove delimiting the flexor tubercle and dorsoventrally high and subrectangular-shaped proximal articular surface ( Fig. 16; Chiappe, 1993;Chiappe and Calvo, 1994;Kurochkin, 1995;Sanz et al., 2002;Chiappe et al., 2006). Enantiornithine birds have been discovered in different Upper Cretaceous units in northern Patagonian (Chiappe and Calvo, 1994;Schweitzer et al., 2002;Agnolín and Martinelli, 2009;Lawver et al., 2011), but their diversity is notably surpassed by the ornithuromorph birds (e.g., Patagopteryx, Alamitornis, Lamarqueavis; Limenavis; Alvarenga and Bonaparte, 1992;Clarke and Chiappe, 2001;Agnolín et al., 2006;Agnolín and Martinelli, 2009;Agnolín, 2010). ...
... Ungual phalanges are referred to enantiornithine birds by virtue of having poorly developed flexor tubercles, a ventral "V" shaped groove delimiting the flexor tubercle and dorsoventrally high and subrectangular-shaped proximal articular surface ( Fig. 16; Chiappe, 1993;Chiappe and Calvo, 1994;Kurochkin, 1995;Sanz et al., 2002;Chiappe et al., 2006). Enantiornithine birds have been discovered in different Upper Cretaceous units in northern Patagonian (Chiappe and Calvo, 1994;Schweitzer et al., 2002;Agnolín and Martinelli, 2009;Lawver et al., 2011), but their diversity is notably surpassed by the ornithuromorph birds (e.g., Patagopteryx, Alamitornis, Lamarqueavis; Limenavis; Alvarenga and Bonaparte, 1992;Clarke and Chiappe, 2001;Agnolín et al., 2006;Agnolín and Martinelli, 2009;Agnolín, 2010). Kookne yeutensis is a derived neornithine bird previously reported from the Chorrillo Formation. ...
Article
The deposits of the Chorrillo Formation (Maastrichtian) were accumulated during a ‘continental window’ that occurred during the Late Cretaceous in the Austral-Magallanes foreland basin, southern Patagonia, Argentina. The aim of the present contribution is to describe the depositional conditions as well as new vertebrate and plant fossils from this unit. The analysis of these deposits resulted in the definition of five architectural elements: Complex sandy narrow sheets channels (SS), Complex gravelly narrow sheets channels (GS), Sandstone lobes (SL), Thick fine-grained deposits (GF) and Thin dark fine-grained deposits (DF). These were separated into channelized and non-channelized units and represent the accumulation in a fine-grained dominated, fossil rich fluvial depositional system. Vertebrates fossil records include two species of frogs of the genus Calypteocephalella (representing the southernmost record of Pipoidea), snakes belonging to Madtsoiidae and Anilioidea (the latter ones being the first records for the basin), chelid turtles similar to Yaminuechelys-Hydromedusa, meiolaniiform turtles, titanosaur sauropods, megaraptoran theropods, new remains of the elasmarian Isasicursor santacrucensis (including the first cranial remains available for this species), hadrosaur ornithischians, enantiornithine birds. Sharks and elasmosaurs are also recorded and may possibly derive from the overlying marine Calafate Formation. These new taxa, together with previous findings from the Chorrillo Formation, are included into a stratigraphic column, thus providing valuable information that sheds new light on faunistic composition and paleobiogeography of high-latitude biotas of Gondwana.
... Both localities yielded notosuchian mesoeucrocodylians (Notosuchus terrestris, Comahuesuchus brachybucalis, and baurusuchids-Wargosuchus australis in "Boca del Sapo" and Baurusuchidae indet. in "Paso Córdoba"-; Woodward, 1896;Gasparini, 1971;Bonaparte, 1991;Martinelli, 2003;Pol, 2005;Martinelli & Pais, 2008;Leardi et al., 2018), snakes (Dinilysia patagonica; Woodward, 1901;Bonaparte, 1991), and small-sized theropod dinosaurs (the abelisauroid Velocisaurus unicus and alvarezsaurids-Alvarezsaurus calvoi in "Boca del Sapo" and Achillesaurus manazzonei in "Paso Córdoba"-; Bonaparte, 1991;Martinelli & Vera, 2007;Brissón Egli et al., 2016). The "Boca del Sapo" locality also includes the mesoeucrocody- lians Microsuchus schilleri (Woodward, 1896;Leardi et al., 2015), Neuquensuchus universitas (Fiorelli & Calvo, 2007;Lio et al., 2018), and peirosaurids (Fiorelli, 2010), the enantiornithine Neuquenornis volans (Chiappe & Calvo, 1994) and egg-clutches with embryos referred to this clade (Schweitzer et al., 2002), and the ornithuromorph Patagopteryx deferrariisi (Alvarenga & Bonaparte, 1992). The mesoeucrocodylian Cynodontosuchus rothi might have been found at this locality (Woodward, 1896), but a precise location is unknown. ...
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The record of Cretaceous terrestrial lizards (Squamata) in South America is patchy, with seven species described from north-eastern and south-eastern Brazil, and few isolated records of iguanians and scincomorphans from the Argentinian Patagonia. Herein we describe a new genus and species of Cretaceous lizard, Paleochelco occultato gen. et sp. nov., based on a partial skull (MACN-Pv-N 120) discovered about three decades ago that was unnoticed in the Colección Paleovertebrados of the Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”. It comes from rocks of the Upper Cretaceous Bajo de la Carpa Formation (Neuquén Group) exposed at the Campus of the Universidad Nacional del Comahue, north of Neuquén City (Neuquén Province). The new taxon was included into a broad phylogenetic dataset of squamates and it was recovered around the base of Polyglyphanodontia in a constrained analysis using a total-evidence backbone. By contrast, the same, but topologically unconstrained analysis found Paleochelco occultato also around the base of Polyglyphanodontia but alternatively as the sister taxon to Polyglyphanodontia + Scleroglossa or as one of the sister taxa to the Mosasauria + Scleroglossa clade. The new finding, as well as other records from Argentina and Brazil, highlights a complex, still unrecovered, evolutionary history for lizards in the Mesozoic of South America.
... Aside from the possibility of digital reconstruction (see Section VI.1), only Archaeopteryx (Alonso et al., 2004;Rauhut, 2014), Neuquenornis (Chiappe & Calvo, 1994), Piscivorenantiornis , Enaliornis (Elzanowski & Galton, 1991), Hesperornis (Elzanowski, 1991), and Ichthyornis (Field et al., 2018b) preserve the occipital region well enough to potentially identify muscular insertions. Of these, only Neuquenornis, Hesperornis, and Ichthyornis preserve any other regions of the skull. ...
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Birds are some of the most diverse organisms on Earth, with species inhabiting a wide variety of niches across every major biome. As such, birds are vital to our understanding of modern ecosystems. Unfortunately, our understanding of the evolutionary history of modern ecosystems is hampered by knowledge gaps in the origin of modern bird diversity and ecosystem ecology. A crucial part of addressing these shortcomings is improving our understanding of the earliest birds, the non‐avian avialans (i.e. non‐crown birds), particularly of their diet. The diet of non‐avian avialans has been a matter of debate, in large part because of the ambiguous qualitative approaches that have been used to reconstruct it. Here we review methods for determining diet in modern and fossil avians (i.e. crown birds) as well as non‐avian theropods, and comment on their usefulness when applied to non‐avian avialans. We use this to propose a set of comparable, quantitative approaches to ascertain fossil bird diet and on this basis provide a consensus of what we currently know about fossil bird diet. While no single approach can precisely predict diet in birds, each can exclude some diets and narrow the dietary possibilities. We recommend combining (i) dental microwear, (ii) landmark‐based muscular reconstruction, (iii) stable isotope geochemistry, (iv) body mass estimations, (v) traditional and/or geometric morphometric analysis, (vi) lever modelling, and (vii) finite element analysis to reconstruct fossil bird diet accurately. Our review provides specific methodologies to implement each approach and discusses complications future researchers should keep in mind. We note that current forms of assessment of dental mesowear, skull traditional morphometrics, geometric morphometrics, and certain stable isotope systems have yet to be proven effective at discerning fossil bird diet. On this basis we report the current state of knowledge of non‐avian avialan diet which remains very incomplete. The ancestral dietary condition in non‐avian avialans remains unclear due to scarce data and contradictory evidence in Archaeopteryx. Among early non‐avian pygostylians, Confuciusornis has finite element analysis and mechanical advantage evidence pointing to herbivory, whilst Sapeornis only has mechanical advantage evidence indicating granivory, agreeing with fossilised ingested material known for this taxon. The enantiornithine ornithothoracine Shenqiornis has mechanical advantage and pedal morphometric evidence pointing to carnivory. In the hongshanornithid ornithuromorph Hongshanornis only mechanical advantage evidence indicates granivory, but this agrees with evidence of gastrolith ingestion in this taxon. Mechanical advantage and ingested fish support carnivory in the songlingornithid ornithuromorph Yanornis. Due to the sparsity of robust dietary assignments, no clear trends in non‐avian avialan dietary evolution have yet emerged. Dietary diversity seems to increase through time, but this is a preservational bias associated with a predominance of data from the Early Cretaceous Jehol Lagerstätte. With this new framework and our synthesis of the current knowledge of non‐avian avialan diet, we expect dietary knowledge and evolutionary trends to become much clearer in the coming years, especially as fossils from other locations and climates are found. This will allow for a deeper and more robust understanding of the role birds played in Mesozoic ecosystems and how this developed into their pivotal role in modern ecosystems. Video abstract
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Rinconsaurus caudamirus, from the Bajo de la Carpa Formation (Santonian), Río Negro, Argentina, is represented by several axial and appendicular elements from, at least, four specimens. The axial skeleton of this taxon was described in detail in a recent contribution, pending a complete analysis and description of its appendicular skeleton. This contribution focuses on the description of the appendicular skeleton of Rinconsaurus and its phylogenetic relationships, considering the new information provided here. Rinconsaurus clearly differs from other titanosaurs for the presence of several autapomorphic characters and for a unique association of characters, some of which are also present in lognkosaurians, aeolosaurines and saltasaurines titanosaurs, and by having a scapula with a scapular blade angled 65° with respect to the coracoid articulation, similar to that of Bellusaurus, Dreadnoughtus and Muyelensaurus. Equations for estimating body mass in sauropods based on long bone circumference suggest a body mass of at least 3-5 tonnes for the largest individuals of Rinconsaurus, being lighter than saltasaurines, but heavier than aeolosaurines. Rinconsaurus was incorporated into an expanded version of a phylogenetic data matrix along with several ontemporary South American titanosaurs. The resulting data matrix comprises 102 taxa scored for 431 characters, and our phylogenetic analysis retrieves Rinconsaurus as a member of the clade Rinconsauria. For its part, the clade Rinconsauria, in which Aeolosaurini is nested, is recovered within a diverse Lognkosauria. When the resulting trees are time calibrated and taking into account the position of Ninjatitan within Rinconsauria, there results that the possible origin of the clades Lognkosauria and Rinconsauria (among other titanosaur clades) could have occurred towards the beginning of the Early Cretaceous.
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Unenlagia comahuensis was originally described as a phylogenetic link between nonavian dinosaurs and birds. Later it was interpreted by some authors as belonging to the deinonychosaurian clade Dromaeosauridae, and more recently as phylogenetically closer to birds than to dromaeosaurids. The only known specimen is represented by an incomplete skeleton, including vertebrae, incomplete scapular girdle, pelvis, and limbs, coming from Upper Cretaceous beds of Neuquén province, Patagonia, Argentina. The aim of the present paper is to include a detailed anatomical description of Unenlagia (currently only known by preliminary descriptions). Detailed analysis of Unenlagia anatomy resulted in the recognition of one possible additional Unenlagiidae synapomorphy (i.e., the presence of cup‐like iliac articulation on ischium). We recognize derived anatomical traits that Unenlagia and kin share with birds, lending support to the interpretation that unenlagiids are stem‐Avialae. Particularly, some appendicular features (e.g., scapula with subtriangular and relatively reduced acromion, poor outward projection of the glenoid and glenoidal lips on the scapula, lateral orientation of scapular glenoid, craniolaterally oriented deltopectoral crest of humerus) may be related to the acquisition of anatomical novelties that in birds are associated with flight. The present contribution on Unenlagia provides new data regarding the early evolution of avian features.
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Several characters of the tarsometatarsus of the Cretaceous enantiornithine birds are discussed, with emphasis on the genus Avisaurus, which was considered a non-avian theropod taxon by its authors. Two synapomorphies (metatarsal IV reduced with respect to metatarsals II and III; well-developed knob on the anterior face of metatarsal II) relate Avisaurus to the remaining enantiornithine tarsometatarsi types and support reference of this taxon within the Enantiornithes. Three other synapomorphies (laterally compressed, J-shaped metatarsal I; anterior surface of the mid-shaft of metatarsal III strongly convex transversely; strong posterior projection of the internal rim of trochlea on metatarsal III) shared by Avisaurus and a Late Cretaceous enantiornithine from northwestern Patagonia further support its avian affinities. Avisaurus and the family Avisauridae are assigned to the avian subclass Enantiornithes.
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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