How Birds got Their Wings

Tracing the Origin & Evolution of Bird Reproduction in Dinosaurs

What really did come first--the chicken or the egg? Birds' reproductive biology is dramatically different from that of any other living vertebrates, and ornithologists and paleontologists have long wondered how and when the unique features of bird reproduction originated. A new Review in The Auk: Ornithological Advances examines answers from three sources--modern birds, fossils of primitive birds, and fossils of the dinosaurs from which birds are descended--to shed new light on the subject.

All modern birds share certain reproductive features, such as a single functional ovary and the practice of incubating their eggs through direct contact. Analysis of the bird family tree also suggests that early birds built simple, open nests on the ground and that their young were "precocial," meaning they were well-developed and almost ready to fend for themselves when they hatched. Those dinosaurs close to the ancestry of birds shared some of these traits, but they had two functional reproductive tracts, and their eggs were smaller relative to their body size and more elongated than those of modern birds.

Fossils of primitive birds and eggs from the Mesozoic era place them midway between their dinosaur ancestors and their modern descendants, with eggs between those of pre-avian dinosaurs and modern birds in term of size and shape. In this way, David Varricchio and Frankie Jackson of the Montana State University are able to trace the evolution of bird reproduction through a series of distinct stages, from pre-avian dinosaurs to the birds of today.

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Dinosaurs Probably had Color Vision

Earlier this year, scientists used zebra finches to pinpoint the gene that enables birds to produce and display the colour red.

Now, a new study shows the same 'red gene' is also found in turtles, which share an ancient common ancestor with birds. Both share a common ancestor with dinosaurs.

The gene, called CYP2J19, allows birds and turtles to convert the yellow pigments in their diets into red, which they then use to heighten colour vision in the red spectrum through droplets of red oil in their retinas.

Birds and turtles are the only existing tetrapods, or land vertebrates, to have these red retinal oil droplets. In some birds and a few turtle species, red pigment produced by the gene is also used for external display: red beaks and feathers, or the red neck patches and rims of shells seen in species such as the painted turtle.

The scientists mined the genetic data of various bird and reptile species to reconstruct an evolutionary history of the CYP2J19 gene, and found that it dated back hundreds of millions of years in the ancient archelosaur genetic line - the ancestral lineage of turtles, birds and dinosaurs.

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Turtles are probably archosaurs, btw.

Extraorindary Fossil of Ostrich Relative Found in Eocene Paleogene North America

Exceedingly well-preserved bird fossil specimens dating 50 million years represent a new species that is a previously unknown relative of the modern-day ostrich, according to a new paper co-authored by Sterling Nesbitt of Virginia Tech's College of Science and part of the university's Global Change Center.

The bird fossils were found more than a decade ago, completely intact with bones, feathers, and soft tissues in a former lake bed in Wyoming. Nesbitt cannot hide a grin as he calls the fossil a once-in-a-lifetime discovery for paleontologists.

"This is among one of the earliest well-represented bird species after the age of large dinosaurs," said Nesbitt, an assistant professor in the Department of Geosciences.

"You can definitely appreciate how complete these fossil are," added Nesbitt of the remains, the focus of a research paper co-authored by Nesbitt and newly published in the Bulletin of the American Museum of Natural History.

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Baby Enantiornithine (Bird) Wings Preserved in Amber From Middile Cretaceous Burma

Mummified precocial bird wings in mid-Cretaceous Burmese amber

Authors:

Xing et al

Abstract:

Our knowledge of Cretaceous plumage is limited by the fossil record itself: compression fossils surrounding skeletons lack the finest morphological details and seldom preserve visible traces of colour, while discoveries in amber have been disassociated from their source animals. Here we report the osteology, plumage and pterylosis of two exceptionally preserved theropod wings from Burmese amber, with vestiges of soft tissues. The extremely small size and osteological development of the wings, combined with their digit proportions, strongly suggests that the remains represent precocial hatchlings of enantiornithine birds. These specimens demonstrate that the plumage types associated with modern birds were present within single individuals of Enantiornithes by the Cenomanian (99 million years ago), providing insights into plumage arrangement and microstructure alongside immature skeletal remains. This finding brings new detail to our understanding of infrequently preserved juveniles, including the first concrete examples of follicles, feather tracts and apteria in Cretaceous avialans.

Sexual Dimorphism in Miocene Neogene Mihirung Dromornis stirtoni

Sexual dimorphism in the late Miocene mihirung Dromornis stirtoni (Aves: Dromornithidae) from the Alcoota Local Fauna of central Australia

Authors:

Handley et al

Abstract:

The dromornithids were giant flightless birds endemic to Australia from the late Paleogene to the late Pleistocene. Dromornithids are generally considered to be divergent members of the Anseriformes, but they display many convergent features with extant ratites. In this study, we investigate Dromornis stirtoni from the Alcoota Local Fauna, a species for which little is known of its biology. We used traditional methods of comparative morphology, mass estimation, landmark-based morphometrics, and histological investigations to determine the presence of medullary bone, to assess the possible presence, form, and extent of sexual dimorphism in D. stirtoni. Two morphological groups were identified for each main leg element, differing primarily in relative robustness. Core samples from femora and tibiotarsi shafts revealed medullary bone in the less robust morph, indicating that these were females. Mass, as estimated by algorithms applied to our preferred measurement of least-shaft circumference of tibiotarsi, was significantly different between males (mean = 528 kg) and females (mean = 451 kg). Therefore, male D. stirtoni were more robust but not much taller than the females and challenge the elephant bird, Aepyornis maximus, for the title of the most massive bird to have existed. Sexual dimorphism in this largest of all dromornithids, therefore, was like that of extant Anseriformes. We infer long-term monogamy, mutual display, shared parental care, female incubation, and aggressive defense of nests in these birds. The techniques of geometric morphometrics applied in this study maximize the use of fragmentary material, helping to overcome the common paleontological challenge of limited sample sizes.

Tetrapod Zoology on The Maniraptor Dinosaurs Part 2

In this second article on maniraptorans, we look at the main groups that constitute this clade: you’ll need to remember the main group names if the trends and tendencies discussed in later parts of this series are to make any sense. The previous article – part 1 – looked briefly at maniraptoran origins and at the fact that maniraptorans are nested within coelurosaurian theropods. Ok, onwards…

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A Fish-Eating Enantiornithine Bird had Digestive Pellets

A Fish-Eating Enantiornithine Bird from the Early Cretaceous of China Provides Evidence of Modern Avian Digestive Features

Authors:

Wang et al

Abstract:

Modern birds differ from their theropod ancestors in lacking teeth and heavily constructed bony jaws, having evolved a lightly built beak and a specialized digestive system capable of processing unmasticated food [ 1, 2 ]. Enantiornithes, the most successful clade of Mesozoic birds, represents the sister group of the Ornithuromorpha, which gave rise to living birds [ 3 ]. Nevertheless, the feeding habits of enantiornithines have remained unknown because of a lack of fossil evidence. In contrast, exceptionally preserved fossils reveal that derived avian features were present in the digestive systems of some non-enantiornithine birds with ages exceeding 125 million years [ 4, 5 ]. Here, we report a new piscivorous enantiornithine from the Early Cretaceous Jehol Biota of China. This specimen preserves a gastric pellet that includes fish bones. The new enantiornithine, like many modern piscivores and raptors, seems to have swallowed its prey whole and regurgitated indigestible materials such as bones, invertebrate exoskeletons, scales, and feathers. This fossil represents the oldest unambiguous record of an avian gastric pellet and the only such record from the Mesozoic. The pellet points to a fish diet and suggests that the alimentary tract of the new enantiornithine resembled that of extant avians in having efficient antiperistalsis and a two-chambered stomach with a muscular gizzard capable of compacting indigestible matter into a cohesive pellet. The inferred occurrence of these advanced features in an enantiornithine implies that they were widespread in Cretaceous birds and likely facilitated dietary diversification within both Enantiornithes and Ornithuromorpha.

Did Seed Eating Save the Birds at the Cretaceous Paleogene Extinction?

When the dinosaurs became extinct, plenty of small bird-like dinosaurs disappeared along with giants like Tyrannosaurus and Triceratops. Why only some of them survived to become modern-day birds remains a mystery. Now, researchers reporting April 21 in Current Biology suggest that abrupt ecological changes following a meteor impact may have been more detrimental to carnivorous bird-like dinosaurs, and early modern birds with toothless beaks were able to survive on seeds when other food sources declined.

"The small bird-like dinosaurs in the Cretaceous, the maniraptoran dinosaurs, are not a well-understood group," says first author Derek Larson, a paleontologist at the Philip J. Currie Dinosaur Museum in Alberta and PhD candidate at the University of Toronto. "They're some of the closest relatives to modern birds, and at the end of the Cretaceous, many went extinct, including the toothed birds—but modern crown-group birds managed to survive the extinction. The question is, why did that difference occur when these groups were so similar?"

The team of researchers, which also included David Evans of the Royal Ontario Museum and the University of Toronto and Caleb Brown of the Royal Tyrrell Museum of Paleontology, began by investigating whether the extinction at the end of the Cretaceous was an abrupt event or a progressive decline simply capped off by the meteor impact. The fossil record holds evidence to support both scenarios, depending on which dinosaurs are being examined.

Delving into the bird-like dinosaurs, Larson collected data describing 3,104 fossilized teeth from four different maniraptoran families. Some were already published, but much of the information came from Larson's own work at the microscope, cataloging the shape and size of each tooth.

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These are not the Paleogene Penguins you are Looking for

New late Eocene and Oligocene remains of the flightless, penguin-like plotopterids (Aves, Plotopteridae) from western Washington State, U.S.A.

Authors:

Mayr et al

Abstract:

We describe new plotopterids (Aves, Plotopteridae) from late Eocene and Oligocene strata in western Washington State, U.S.A. The specimens belong to four new species of these flightless, wing-propelled seabirds, three of which are named and assigned to two new supraspecific taxa, Olympidytes, gen. nov., and Klallamornis, gen. nov. We confirm previous observations on a high diversity of plotopterids in the Paleogene of North America, but because the fossils are from different formations, it remains elusive how many of the six currently recognized species from western Washington actually coexisted. Tonsala, the only previously described plotopterid taxon from the Olympic Peninsula, is likely to occupy a more basal phylogenetic position than the other plotopterids of this geographic area. Olympidytes and Klallamornis may be successive sister taxa of Copepteryx and Hokkaidornis from the late Oligocene of Japan, but a determination of the exact affinities of the new taxa requires the discovery of further fossils. Notably, the geochronologically youngest plotopterid, the early Miocene Plotopterum, differs from earlier taxa in plesiomorphic features and is here considered to be among the phylogenetically most basal plotopterids. The late Eocene basal Phocavis likewise temporally overlaps with more derived plotopterid taxa. The coexistence of basal and more derived plotopterids in the late Eocene may indicate a rapid evolution of plotopterids towards the late Eocene. The factors that allowed the persistence of basal taxa into the Miocene remain, however, elusive, and so are those that triggered the evolution of wing-propelled diving in these highly specialized birds.

Predictable evolution toward flightlessness in volant island birds

Predictable evolution toward flightlessness in volant island birds

Authors:

Wright et al

Abstract:

Birds are prolific colonists of islands, where they readily evolve distinct forms. Identifying predictable, directional patterns of evolutionary change in island birds, however, has proved challenging. The “island rule” predicts that island species evolve toward intermediate sizes, but its general applicability to birds is questionable. However, convergent evolution has clearly occurred in the island bird lineages that have undergone transitions to secondary flightlessness, a process involving drastic reduction of the flight muscles and enlargement of the hindlimbs. Here, we investigated whether volant island bird populations tend to change shape in a way that converges subtly on the flightless form. We found that island bird species have evolved smaller flight muscles than their continental relatives. Furthermore, in 366 populations of Caribbean and Pacific birds, smaller flight muscles and longer legs evolved in response to increasing insularity and, strikingly, the scarcity of avian and mammalian predators. On smaller islands with fewer predators, birds exhibited shifts in investment from forelimbs to hindlimbs that were qualitatively similar to anatomical rearrangements observed in flightless birds. These findings suggest that island bird populations tend to evolve on a trajectory toward flightlessness, even if most remain volant. This pattern was consistent across nine families and four orders that vary in lifestyle, foraging behavior, flight style, and body size. These predictable shifts in avian morphology may reduce the physical capacity for escape via flight and diminish the potential for small-island taxa to diversify via dispersal.

New Remains of Late Cretaceous Giant Bird Gargantuavis philoinos Found in France

New remains of the giant bird Gargantuavis philoinos from the Late Cretaceous of Provence (south-eastern France)

Authors:

Buffetaut et al

Abstract:

Two incomplete pelves of the giant bird Gargantuavis philoinos are described from Late Cretaceous deposits at Fox-Amphoux (Var, south-eastern France). They consist of synsacra with attached parts of the ilia. One of them has undergone considerable dorsoventral compression, which makes it very similar in appearance to the holotype pelvis of Gargantuavis philoinos from Campagne-sur-Aude (Aude, southern France). The second specimen has suffered some lateral distortion but is uncrushed dorsoventrally. Because of this, its avians characters (including an arched synsacrum and widespread pneumatisation) are especially clear. These new specimens confirm the avian nature of Gargantuavis and reveal new details about its pelvic anatomy, but provide little new evidence about its systematic position within Aves. The geographical distribution and general rarity of Gargantuavis are discussed.

Giant Terrestrial Bird Gastornis Wandered the Eocene Paleogene Arctic of Canada

The palaeobiology of high latitude birds from the early Eocene greenhouse of Ellesmere Island, Arctic Canada

Authors:

Stidham et al

Abstract:

Fossils attributable to the extinct waterfowl clade Presbyornithidae and the large flightless Gastornithidae from the early Eocene (~52–53 Ma) of Ellesmere Island, in northernmost Canada are the oldest Cenozoic avian fossils from the Arctic. Except for its slightly larger size, the Arctic presbyornithid humerus is not distinguishable from fossils of Presbyornis pervetus from the western United States, and the Gastornis phalanx is within the known size range of mid-latitude individuals. The occurrence of Presbyornis above the Arctic Circle in the Eocene could be the result of annual migration like that of its living duck and geese relatives, or it may have been a year-round resident similar to some Eocene mammals on Ellesmere and some extant species of sea ducks. Gastornis, along with some of the mammalian and reptilian members of the Eocene Arctic fauna, likely over-wintered in the Arctic. Despite the milder (above freezing) Eocene climate on Ellesmere Island, prolonged periods of darkness occurred during the winter. Presence of these extinct birds at both mid and high latitudes on the northern continents provides evidence that future increases in climatic warming (closer to Eocene levels) could lead to the establishment of new migratory or resident populations within the Arctic Circle.

Evidence a Young Flightless Cretaceous Bird Hesperornis Escaped a Plesiosaur attack

Hesperornis escapes plesiosaur attack

Authors:

Martin et al

Abstract:

Evidence from the Pierre Shale (Late Cretaceous) of South Dakota is presented for an attack on a juvenile Hesperornis by a polycotylid plesiosaur. The wound healed and the Hesperornis grew to maturity. Evidence of survival provides our best information about predator prey interactions in the fossil record but are rare for birds where survival is an unlikely outcome.

Chongmingia zhengi: A New Basal Bird From Early Cretaceous China

a questionable reconstruction given there's no skull in the fossil

Over the past three decades, representatives of all major Mesozoic bird groups have been reported from the Early Cretaceous Jehol Biota of northeastern China. A new species, Chongmingia zhengi, reported in the journal of Scientific Reports on 25 January 2016, sheds light on the early evolution of birds. Phylogenetic analyses indicate that it is basal to the dominant Mesozoic avian clades Enantiornithes and Ornithuromorpha, and represents a new basal avialan lineage. This new discovery adds to our knowledge regarding the phylogenetic differentiation and morphological diversity in early avian evolution.

This new species, represented by a single new skeleton from the Early Cretaceous Jiufotang Formation of the Jehol Group in Dapingfang, Liaoning Province, China. The generic name is from the Mandarin word Chongming, referring to a Chinese mythological bird. The specific epithet is in honour of Mr. Xiaoting Zheng for his generous contribution in the establishment of the Shandong Tianyu Museum of Nature.

The new specimen is a partial skeleton with associated soft tissues and gastroliths, missing the skull and most of the caudal vertebrae. Comparative studies indicate that it is a large non-ornithothoracine bird distinguishable from the known basal avialans by a combination of features.

The furcula of Chongmingia is rigid (reducing its efficiency), consequently requiring more power for flight. However, the elongated forelimb and the large deltopectoral crest on the humerus might indicate that the power was available. The unique combination of features present in this species demonstrates that numerous evolutionary experimentations took place in the early evolution of powered flight.

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Ilbandornis woodburnei: A New Species of Oligocene/Miocene Flightless Mihirung

The extinct flightless mihirungs (Aves, Dromornithidae): cranial anatomy, a new species, and assessment of Oligo-Miocene lineage diversity

Authors:

Worthy et al

Abstract:

Giant flightless fowl (Aves, Dromornithidae) similar to the Northern Hemisphere gastornithids and weighing up to 350–650 kg evolved on Gondwana and existed in what is now Australia from the Eocene to the late Quaternary. Understanding cranial morphology of dromornithids has until now been based almost wholly on species of Dromornis, with that of species in three other genera either previously unknown or very fragmentary. Here we rectify this deficiency and describe a well-preserved cranium from the middle Miocene Bullock Creek Local Fauna referred to Ilbandornis woodburnei, rich, fragmentary crania, quadrates, pterygoids, and mandibles for the Oligo-Miocene Barawertornis tedfordi Rich, and additional material of the species of Ilbandornis. The morphological similarity of this cranial material suggests that the emu-sized B. tedfordi is a smaller precursor to and differs little from species of Ilbandornis. Dromornis murrayi, n. sp., from late Oligocene–Early Miocene sites at Riversleigh, based on cranial and postcranial elements, is the oldest and smallest species in its genus. Placed in the context of other data, these observations suggest that the dromornithids comprised only two lineages throughout the Oligo-Miocene. The Barawertornis-Ilbandornis lineage attained maximum diversity in the middle Miocene Bullock Creek and late Miocene Alcoota local faunas (LF), with two species in each, but the Dromornis lineage seems to have been monotypic throughout its temporal range. The low diversity of these giant galloanseres in Australia mirrors that of the giant herbivorous ratites (ostriches and kin), which similarly have low diversity where they coevolved with diverse mammalian faunas.

Feitianius paradisi: a new Ornithothoracid Enantiornithine Bird With Elaborate Tail Ornamentation From Aptian Cretaceous China

A new Early Cretaceous enantiornithine (Aves, Ornithothoraces) from northwestern China with elaborate tail ornamentation

Authors:

O'Connor et al

Abstract:

We provide a detailed description of a well-preserved enantiornithine specimen (GSGM-05-CM-004) from the Lower Cretaceous (Aptian) Xiagou Formation of northwestern Gansu Province, China, for which we erect the new taxon Feitianius paradisi, gen. et sp. nov. This specimen has a distinctive pelvic morphology and can be further distinguished from all other Mesozoic birds by a unique caudal plumage formed by multiple rectricial morphotypes. This newly documented tail morphology reveals a previously unrecognized level of complexity in the plumage of basal birds. This complex tail-feather morphology has a parallel in extant sexually dimorphic birds in which the males have the most altered tails; thus, we identify this specimen as male. Ornamental tail morphologies, such as the novel tail plumage described here, dominate Enantiornithes. This reinforces hypotheses that sexual selection was a major driving force in the evolution of basal bird plumage.

Did Modern Birds Evolve in Turonian/Coniacian Cretaceous South America and Spread Worldwide After K-Pg/K-T Mass Extinction

New research led by the American Museum of Natural History reveals that the evolution of modern birds was greatly shaped by the history of our planet's geography and climate. The DNA-based work, published today in the journal Science Advances, finds that birds arose in what is now South America around 90 million years ago, and radiated extensively around the time of the Cretaceous-Paleogene extinction event that killed off the non-avian dinosaurs. The new research suggests that birds in South America survived this event and then started moving to other parts of the world via multiple land bridges while diversifying during periods of global cooling.

"Modern birds are the most diverse group of terrestrial vertebrates in terms of species richness and global distribution, but we still don't fully understand their large-scale evolutionary history," said Joel Cracraft, a curator in the Museum's Department of Ornithology and co-author of the paper. "It's a difficult problem to solve because we have very large gaps in the fossil record. This is the first quantitative analysis estimating where birds might have arisen, based on the best phylogenetic hypothesis that we have today."

Cracraft and lead author Santiago Claramunt, a research associate in the Museum's Department of Ornithology, analyzed DNA sequences for most modern bird families with information from 130 fossil birds to generate a new evolutionary time tree.

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Southern Chickadees Moving North, Will Invade Canada Under Global Warming

Biologists know that climate change is causing southern species' ranges to move northward in the Northern Hemisphere. But little research has been done on the indirect ways climate change is influencing biodiversity, such as the poleward migration's impact on the ranges of species already residing in the north. What will the distribution of species look like across North America in the year 2050?

New research on northern (black-capped) and southern (Carolina) species of chickadees offers some answers. Amber Rice, assistant professor of biological science at Lehigh and her co-author Michael A. McQuillan, a graduate student studying integrative and evolutionary biology, looked at the predicted effects of climate change on both species of chickadee with an eye toward examining how rising temperatures are influencing their location. They also looked at how other matters are factoring in to the species' range limits - such as interactions between the species, like hybridization, which is when individuals from different species mate and produce offspring.

Findings from the study, published in a paper called "Differential effects of climate and species interactions on range limits at a hybrid zone: potential direct and indirect impacts of climate change" in the November 2015 edition of Ecology and Evolution, have implications beyond chickadees.

"We found that climate change can both directly and indirectly affect species distributions and hybrid zone location," says McQuillan. "Additionally, our results lend support to the hypothesis that physical factors regulate species' poleward range limits, while biological factors shape range limits near the equator."

To begin the study, Rice and McQuillan collected information about where each of the chickadee species occurs and recorded climate information from each location where the birds have been observed. Then they projected the data onto a map and identified areas where the climate is most suitable for each species. When they compared the suitable areas to the areas where the birds are actually located, they found that the northern species was often absent from large areas with suitable climate.

"We speculated that the lack of the northern chickadee species in areas you would expect them to be could be attributed to competition or hybridization," said Professor Rice. "We discovered that the two types of chickadees are being affected differently: the southern species--the Carolina chickadee--is being pushed north due to climate change and the northern species--the black-capped chickadees--are being displaced by the southern species of chickadees as a result."

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What's in a Wing? Aptian Cretaceous Enantiornithine Bird Shows Perfect Flight Adaptation

Birds have an enormously long evolutionary history: The earliest of them, the famed Archaeopteryx, lived 150 million years ago in what is today southern Germany. However, whether these early birds were capable of flying -- and if so, how well -- has remained shrouded in scientific controversy. A new discovery published in the journal Scientific Reports documents the intricate arrangement of the muscles and ligaments that controlled the main feathers of the wing of an ancient bird, supporting the notion that at least some of the most ancient birds performed aerodynamic feats in a fashion similar to those of many living birds.

An international team of Spanish paleontologists and NHM's Director of the Dinosaur Institute, Dr. Luis M. Chiappe, studied the exceptionally preserved wing of a 125-million-year-old bird from central Spain. Beyond the bones preserved in the fossil, the tiny wing of this ancient bird reveals details of a complex network of muscles that in modern birds controls the fine adjustments of the wing's main feathers, allowing birds to master the sky.

"The anatomical match between the muscle network preserved in the fossil and those that characterize the wings of living birds strongly indicates that some of the earliest birds were capable of aerodynamic prowess like many present-day birds," said Chiappe, the investigation's senior scientist.

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open access paper link.