Abstract The first evidence of a Bird in strata of the Oxfordian or Corallian stage of the Oolitic series was afforded by the impression of a single feather, in a slab of the lithographic calcareous laminated stone, or slate, of Solenhofen; it is described and figured with characteristic minuteness and care by M. Hermann von Meyer, in the fifth part of the ‘Jahrbuch für Mineralogie.’ He applies to this fossil impression the term Archeopteryx lithographica; and although the probability is great that the class of Birds was represented by more than one genus at the period of the deposit of the lithographic slate, and generic identity cannot be predicated from a solitary feather, I shall assume it in the present instance, and retain for the genus, which can now be established on adequate characters, the name originally proposed by the distinguished German palaeontologist. At the Meeting of the Mathematico-Physical Class of the Royal Academy of Sciences of Munich, on the 9th of November, 1861, Professor Andreas Wagner communicated the discovery, in the lithographic slate of Solenhofen, of a considerable portion of the skeleton of an animal with impressions of feathers radiating fanwise from each anterior limb, and diverging obliquely in a single series from each side of a long tail.

<h4>Background</h4>Birds are key indicator species in extant ecosystems, and thus we would expect extinct birds to provide insights into the nature of ancient ecosystems. However, many aspects of extinct bird ecology, particularly their diet, remain obscure. One group of particular interest is the bizarre toothed and long-snouted longipterygid birds. Longipterygidae is the most well-understood family of enantiornithine birds, the dominant birds of the Cretaceous period. However, as with most Mesozoic birds, their diet remains entirely speculative.<h4>Results</h4>To improve our understanding of longipterygids, we investigated four proxies in extant birds to determine diagnostic traits for birds with a given diet: body mass, claw morphometrics, jaw mechanical advantage, and jaw strength via finite element analysis. Body mass of birds tended to correspond to the size of their main food source, with both carnivores and herbivores splitting into two subsets by mass: invertivores or vertivores for carnivores, and granivores + nectarivores or folivores + frugivores for herbivores. Using claw morphometrics, we successfully distinguished ground birds, non-raptorial perching birds, and raptorial birds from one another. We were unable to replicate past results isolating subtypes of raptorial behaviour. Mechanical advantage was able to distinguish herbivorous diets with particularly high values of functional indices, and so is useful for identifying these specific diets in fossil taxa, but overall did a poor job of reflecting diet. Finite element analysis effectively separated birds with hard and/or tough diets from those eating foods which are neither, though could not distinguish hard and tough diets from one another. We reconstructed each of these proxies in longipterygids as well, and after synthesising the four lines of evidence, we find all members of the family but Shengjingornis (whose diet remains inconclusive) most likely to be invertivores or generalist feeders, with raptorial behaviour likely in Longipteryx and Rapaxavis.<h4>Conclusions</h4>This study provides a 20% increase in quantitatively supported fossil bird diets, triples the number of diets reconstructed in enantiornithine species, and serves as an important first step in quantitatively investigating the origins of the trophic diversity of living birds. These findings are consistent with past hypotheses that Mesozoic birds occupied low trophic levels.

Unraveling the origins of the character complexes diagnosing major crown clades is one of the greatest challenges in evolutionary biology. These origination events tend to optimize along extraordinarily long stem lineages where the comparative biology of extant lineages is relatively weak in its heuristic power. Here we add to a growing paleontological literature on the evolutionary origins of the modern avi an brain by describing the endocranial casts of two oviraptorosaur dinosaurs, Citipati osmolskae and Khaan mckennai. These fossil data confirm the antiquity of several avian features, including the expanded cerebrum. They also extend our appreciation of both the inherent variability in the brain-skull relationship along the avian stem and the dynamic nature of these crown characters in the earliest history of their expression.

Among the most revolutionary insights emerging from 200 years of research on dinosaurs is that the clade Dinosauria is represented by approximately 11 000 living species of birds. Although the origin of birds among dinosaurs has been reviewed extensively, recent years have witnessed tremendous progress in our understanding of the deep evolutionary origins of numerous distinctive avian anatomical systems. These advances have been enabled by exciting new fossil discoveries, leading to an ever-expanding phylogenetic framework with which to pinpoint the origins of characteristic avian features. The present review focuses on four notable avian systems whose Mesozoic evolutionary history has been greatly clarified by recent discoveries: brain, kinetic palate, pectoral girdle and postcranial skeletal pneumaticity.

Since the start of the twenty-first century, there has been a notable increase in annual publications focusing on dinosaur reproduction and ontogeny with researchers using these data to address a range of macroevolutionary questions about dinosaurs. Ontogeny, which is closely tied to osteological morphological variation, impacts several key research areas, such as taxonomic diversity, population dynamics, palaeoecology, macroevolution, as well as the physiological and reproductive factors driving ecological success. While these broad studies have significantly advanced our understanding of dinosaur evolution, they have also revealed important challenges and areas needing further investigation. In this review, we aim to outline some of these challenges in major research areas linked to dinosaur ontogeny, namely reproductive biology, osteohistological growth strategies, morphological osteological variation and the link between ontogeny and macroevolution. We also offer some recommendations for best practices and promising future research directions. These recommendations include increasing sample sizes through fieldwork and exhaustive use of pre-existing fossil collections, using micro-computed tomography (μCT) scanning methods to increase dataset sizes in a non-destructive manner, methodical collection and reposition of μCT scan data, assessing ontogenetic maturity, establishing consistency in terminology and methods and building comprehensive extant comparative datasets.

Dinosaurs are a diverse group of reptiles of the clade Dinosauria . They first appeared during the Triassic period , between 243 and 233.23 million years ago , although the exact origin and timing of the evolution of dinosaurs is the subject of active research. They became the dominant terrestrial vertebrates after the Triassic–Jurassic extinction event 201.3 million years ago; their dominance continued through the Jurassic and Cretaceous periods. The fossil record demonstrates that birds are modern feathered dinosaurs , having evolved from earlier theropods during the Late Jurassic epoch . As such, birds were the only dinosaur lineage to survive the Cretaceous–Paleogene extinction event approximately 66 million years ago. Dinosaurs can therefore be divided into avian dinosaurs , or birds; and non-avian dinosaurs , which are all dinosaurs other than birds. This article deals primarily with non-avian dinosaurs. Dinosaurs are a varied group of animals from taxonomic , morphological and ecological standpoints. Birds, at over 10,000 living species , are the most diverse group of vertebrates besides perciform fish. Using fossil evidence, paleontologists have identified over 500 distinct genera and more than 1,000 different species of non-avian dinosaurs. Dinosaurs are represented on every continent by both extant species (birds) and fossil remains. Through the first half of the 20th century, before birds were recognized to be dinosaurs, most of the scientific community believed di

However, given that modern birds are endothermic, the dinosaurs that were the immediate ancestors to birds likely were endothermic as well. Some fossil evidence exists for dinosaurian parental care, and comparative biology supports this hypothesis since the archosaur birds and crocodilians both display extensive parental care. Dinosaurs dominated the Mesozoic era, which was known as the “Age of Reptiles.” The dominance of dinosaurs lasted until the end of the Cretaceous, the last period of the Mesozoic era. The Cretaceous-Tertiary extinction resulted in the loss of most of the large-bodied animals of the Mesozoic era. Birds are the only living descendants of one of the major clades of theropod dinosaurs. Visit this site to see a video discussing the hypothesis that an asteroid caused the Cretaceous-Tertiary (KT) extinction. Class Reptilia includes many diverse species that are classified into four living clades. There are the 25 species of Crocodilia, two species of Sphenodontia, approximately 9,200 Squamata species, and about 325 species of Testudines.

Recent discoveries of spectacular dinosaur fossils overwhelmingly support the hypothesis that birds are descended from maniraptoran theropod dinosaurs, and furthermore, demonstrate that distinctive bird characteristics such as feathers, flight, endothermic physiology, unique strategies for reproduction and growth, and a novel pulmonary system originated among Mesozoic terrestrial dinosaurs. The transition from ground-living to flight-capable theropod dinosaurs now probably represents one of the best-documented major evolutionary transitions in life history. Recent studies in developmental biology and other disciplines provide additional insights into how bird characteristics originated and evolved. The iconic features of extant birds for the most part evolved in a gradual and stepwise fashion throughout archosaur evolution. However, new data also highlight occasional bursts of morphological novelty at certain stages particularly close to the origin of birds and an unavoidable complex, mosaic evolutionary distribution of major bird characteristics on the theropod tree. Research into bird origins provides a premier example of how paleontological and neontological data can interact to reveal the complexity of major innovations, to answer key evolutionary questions, and to lead to new research directions. A better understanding of bird origins requires multifaceted and integrative approaches, yet fossils necessarily provide the final test of any evolutionary model.

Uniquely among extant vertebrates, birds possess complex respiratory systems characterised by the combination of small, rigid lungs, extensive pulmonary air sacs that possess diverticula that invade (pneumatise) the postcranial skeleton, unidirectional ventilation of the lungs, and efficient crosscurrent gas exchange. Crocodilians, the only other living archosaurs, also possess unidirectional lung ventilation, but lack true air sacs and postcranial skeletal pneumaticity (PSP). PSP can be used to infer the presence of avian-like pulmonary air sacs in several extinct archosaur clades (non-avian theropod dinosaurs, sauropod dinosaurs and pterosaurs). However, the evolution of respiratory systems in other archosaurs, especially in the lineage leading to crocodilians, is poorly documented. Here, we use µCT-scanning to investigate the vertebral anatomy of Triassic archosaur taxa, from both the avian and crocodilian lineages as well as non-archosaurian diapsid outgroups. Our results confirm previous suggestions that unambiguous evidence of PSP (presence of internal pneumatic cavities linked to the exterior by foramina) is found only in bird-line (ornithodiran) archosaurs. We propose that pulmonary air sacs were present in the common ancestor of Ornithodira and may have been subsequently lost or reduced in some members of the clade (notably in ornithischian dinosaurs). The development of these avian-like respiratory features might have been linked to inferred increases in activity le

AbstractBirds and mammals mostly produce clutches with small numbers of large individual offspring compared to non-bird reptiles, including dinosaurs on the bird-stem lineage. Existing hypotheses for this variation propose links between relative offspring size and large brains or high metabolic rates, but remain incompletely tested. We characterize the allometries of reproductive output traits (clutch mass, clutch size and individual offspring mass) and evaluate their correlates using phylogenetic regressions across 2857 living and extinct amniote species. Across amniotes, species with larger relative brain sizes have larger individual offspring, fewer offspring or both. This signifies a higher maternal investment per offspring in large-brained species, exemplified by birds and mammals. In dinosaurs, large egg sizes evolved shortly before the origin of the bird crown group, coinciding with an evolutionary increase in relative brain mass and suggesting that evolutionary increases in egg/neonate size evolved due to a requirement for greater investment per offspring with increasing brain size. These egg size increases may explain changes to dinosaur nest structure and pelvic anatomy along the bird-stem lineage. Our results provide insights into the evolutionary pressures shaping reproductive strategies and brain size across amniotes, underscoring the significance of these traits in the broader context of amniote diversification.

Birds still share many traits with their dinosaur ancestors, making them the best living group to reconstruct certain aspects of non-avian theropod biology. Bipedal, digitigrade locomotion and parasagittal hindlimb movement are some of those inherited traits. Living birds, however, maintain an unusually crouched hindlimb posture and locomotion powered by knee flexion, in contrast to the inferred primitive condition of non-avian theropods: more upright posture and limb movement powered by femur retraction. Such functional differences, which are associated with a gradual, anterior shift of the centre of mass in theropods along the bird line, make the use of extant birds to study non-avian theropod locomotion problematic. Here we show that, by experimentally manipulating the location of the centre of mass in living birds, it is possible to recreate limb posture and kinematics inferred for extinct bipedal dinosaurs. Chickens raised wearing artificial tails, and consequently with more posteriorly located centre of mass, showed a more vertical orientation of the femur during standing and increased femoral displacement during locomotion. Our results support the hypothesis that gradual changes in the location of the centre of mass resulted in more crouched hindlimb postures and a shift from hip-driven to knee-driven limb movements through theropod evolution. This study suggests that, through careful experimental manipulations during the growth phase of ontogeny, extant birds can pote

353 pages : 26 cm "Issued August 21, 2020." Includes bibliographical references Introduction / Michael Pittman and Xing Xu -- Section 1. Systematics, fossil record, and biogeography -- Chapter 1. Pennaraptoran systematics / Michael Pittman, Jingmai O'Connor, Daniel J. Field, Alan H. Turner, Waisum Ma, Peter Makovicky, and Xing Xu -- Chapter 2. The fossil record of Mesozoic and Paleocene pennaraptorans / Michael Pittman, Jingmai O'Connor, Edison Tse, Peter Makovicky, Daniel J. Field, Waisum Ma, Alan H. Turner, Mark A. Norell, Rui Pei, and Xing Xu -- Chapter 3. The impact of unstable taxa in coelurosaurian phylogeny and resampling support measures for parsimony analyses / Diego Pol and Pablo A. Goloboff -- Chapter 4. The biogeography of coelurosaurian theropods and its impact on their evolutionary history / Anyang Ding, Michael Pittman, Paul Upchurch, Jingmai O'Connor, Daniel J. Field, and Xing Xu -- Chapter 5. Timing the extant avian radiation : the rise of modern birds, and the importance of modeling molecular rate variation / Daniel J. Field, Jacob S. Berv, Allison Y. Hsiang, Robert Lanfear, Michael J. Landis, and Alex Dornburg -- Section 2. Anatomical frontiers -- Chapter 6. Disparity and macroevolutionary transformation of the maniraptoran manus / Sergio M. Nebreda, Guillermo Navalón, Iris Menéndez, Trond Sigurdsen, Luis M. Chiappe, and Jesús Marugán-Lobón -- Chapter 7. Tooth vs. beak : the evolutionary developmental control of the avian feeding apparatus / Shuo Wang, Jose

Rather, Saurischia diverged into two groups: One included the long-necked herbivorous dinosaurs, such as Apatosaurus. The second group, bipedal predators called theropods, gave rise to birds. This course of evolution is highlighted by numerous similarities between late (maniraptoran) theropod fossils and birds, specifically in the structure of the hip and wrist bones, as well as the presence of the wishbone, formed by the fusion of the clavicles. The clade Neornithes includes the avian crown group, which comprises all living birds and the descendants from their most recent common maniraptoran ancestor. One well-known and important fossil of an animal that appears “intermediate” between dinosaurs and birds is Archaeopteryx (Figure 29.35), which is from the Jurassic period (200 to 145 MYA). Archaeopteryx has characteristics of both maniraptoran dinosaurs and modern birds. Some scientists propose classifying it as a bird, but others prefer to classify it as a dinosaur. Traits in skeletons of Archaeopteryx like those of a dinosaur included a jaw with teeth and a long bony tail.

Richard Prum's (2002) rancorous, unreviewed essay on the theropod origin of birds is a one-sided view of a difficult problem, full of anatomical misconceptions that are highly misleading, and advocates that (p. 13), "it is time to abandon debate on the theropod origin of birds." His article is essentially a restatement and defense of a current dogma of paleontology-that birds are living dinosaurs, directly descended from, or having shared common ancestry with, one of the most highly derived and specialized groups of Cretaceous theropods, the dromaeosaurs (and Cretaceous troodontids), that are presumed to have had ghost lineages going back into the Jurassic Period. Advocates on both sides of the debate agree that birds are related to dinosaurs, but opponents of the birds-are-dinosaurs movement, including myself, advocate a common shared ancestry of birds and dinosaurs from basal archosaurs, with less specialized anatomical baggage, at a much earlier time. The "birds are living dinosaurs" hypothesis dates back almost three decades to when John Ostrom (see Ostrom 1976), combining studies of his earlier discovery of the late, early Cretaceous dromaeosaur Deinonychus with his speculations on hot-blooded (endothermic) dinosaurs, presented his new dinosarurian origin of birds theory. At its inception, all theropods were highly energized, endothermic reptiles (endothermic homeotherms), and the smaller theropods had acquired feathers for insulation. Archaeopteryx was an earthbound fea

evolution of birds began in the Jurassic Period, with the earliest birds derived from a clade of theropod dinosaurs named Paraves. Birds are categorized The evolution of birds began in the Jurassic Period, with the earliest birds derived from a clade of theropod dinosaurs named Paraves. Birds are categorized as a biological class, Aves. For more than a century, the small theropod dinosaur Archaeopteryx lithographica from the Late Jurassic period was considered to have been the earliest bird. Modern phylogenies place birds in the dinosaur clade Th T…

living allies of the dinosaurs are the crocodiles and the ratite birds (ostrich, etc.), which, with the more primitive dinosaurs , were probably descended from