Cretaceous Birds Research Articles

Mesozoic birds of China—a synoptic review

A synoptic review of the discoveries and studies of Chinese Mesozoic birds is provided in this paper. 40Ar/39Ar dating of several bird-bearing deposits in the Jehol Group has established a geochronological framework for the study of the early avian radiation. Chinese Mesozoic birds had lasted for at least 11 Ma during about 131 Ma and 120 Ma (Barremian to Aptian) of the middle and late Early Cretaceous, respectively. In order to further evaluate the change of the avian diversity in the Jehol Biota, six new orders and families are erected based on known genera and species, which brings the total number of orders of Chinese Mesozoic birds to 15 and highlights a remarkable radiation ever since the first appearance of birds in the Late Jurassic. Chinese Early Cretaceous birds had experienced a significant differentiation in morphology, flight, diet and habitat. Further examination of the foot of Jeholornis suggests this bird might not have possessed a fully reversed hallux. However, the attachment of metatarsal I to the medial side of metatarsal II does not preclude trunk climbing, a pre-adaptation for well developed perching life of early birds. Arboreality had proved to be a key adaptation in the origin and early evolution of bird flight, and the adaptation to lakeshore environment had played an equally important role in the origin of ornithurine birds and their near-modern flight skill. Many Chinese Early Cretaceous birds had preserved the direct evidence of their diet, showing that the most primitive birds were probably mainly insectivorous and that specialized herbivorous or carnivorous (e.g., piscivorous) dietary adaptation had appeared only in later advanced forms. The only known Early Cretaceous bird embryo fossil has shown that precocial birds had occurred prior to altricial birds in avian history, and the size of the embryo and other analysis indicate it probably had a short incubation period. Leg feathers probably have a wide range of distribution in early birds, further suggesting that leg feathers had played a key role in the beginning stage of the flight of birds. Finally, the Early Cretaceous avian radiation can be better understood against the background of their unique ecosystem. The advantage of birds in the competitions with other vertebrate groups such as pterosaurs had probably not only resulted in the rapid differentiation and radiation of birds but also the worldwide spreading of pterosaurs and other vertebrates from East Asia in the Early Cretaceous.

Juvenile Birds from the Early Cretaceous of China: Implications for Enantiornithine Ontogeny

Mesozoic remains of embryonic and early juvenile birds are rare. To date, a handful of in ovo embryos and early juveniles of enantiornithines from the Early Cretaceous of China and Spain and the Late Cretaceous of Mongolia and Argentina have comprised the entire published record of perinatal ontogenetic stages of Mesozoic birds. We report on the skeletal morphology of three nearly complete early juvenile avians from the renowned Early Cretaceous Yixian Formation of Liaoning Province in northeastern China. Evidence of the immaturity of these specimens is expressed in the intense grooving and pitting of the periosteal surfaces, the disproportionately small size of the sterna, and the relative size of the skull and orbits. Size notwithstanding, anatomical differences between these three specimens are minimal, leaving no basis for discriminating them into separate taxa. Numerous osteological synapomorphies indicate that they are euenantiornithine birds, the most diverse clade of Enantiornithes, but their identification as members of a particular euenantiornithine taxon remains unclear. Their early ontogenetic stage, however, provides important information about the postnatal development of this specious clade of Cretaceous birds. The presence of pennaceous wing feathers suggests that fledging occurred very early in ontogeny, thus supporting a precocial or highly precocial strategy for enantiornithine hatchlings. The morphology of these new early-stage juveniles is also significant in that they allow a better understanding of the homologies of several avian compound bones because the components of these skeletal compounds are preserved prior to their coossification. The general morphology of the wrist and ankle of these juveniles highlights once again the striking similarity between nonavian theropods and early birds.

A new Enantiornithine bird from the Late Cretaceous of the Gobi desert

Synopsis We report on a new species of enantiornithine bird from the Late Cretaceous of the Mongolian Gobi Desert, which adds to the meager record of birds from the latest part of the Mesozoic in this region. The exceptional, three‐dimensional bones of the new fossil increase the known anatomical diversity of enantiornithine birds, providing information about previously unreported morphologies such as a pneumatised furcula. Several synapomorphies nest the new bird within an enantiornithine clade of proficient fliers, but the anatomy and proportions of its flight apparatus imply significant aerodynamic restrictions. The combination of phylogeny and our functional interpretation suggests that this new fossil bird is a representative of a flightless lineage. This discovery thus provides the first evidence of a trend towards more limited flying capabilities among Enantiornithes, a group of Cretaceous birds otherwise believed to be represented by competent fliers.

Early Penguin Fossils, Plus Mitochondrial Genomes, Calibrate Avian Evolution

Testing models of macroevolution, and especially the sufficiency of microevolutionary processes, requires good collaboration between molecular biologists and paleontologists. We report such a test for events around the Late Cretaceous by describing the earliest penguin fossils, analyzing complete mitochondrial genomes from an albatross, a petrel, and a loon, and describe the gradual decline of pterosaurs at the same time modern birds radiate. The penguin fossils comprise four naturally associated skeletons from the New Zealand Waipara Greensand, a Paleocene (early Tertiary) formation just above a well-known Cretaceous/Tertiary boundary site. The fossils, in a new genus (Waimanu), provide a lower estimate of 61-62 Ma for the divergence between penguins and other birds and thus establish a reliable calibration point for avian evolution. Combining fossil calibration points, DNA sequences, maximum likelihood, and Bayesian analysis, the penguin calibrations imply a radiation of modern (crown group) birds in the Late Cretaceous. This includes a conservative estimate that modern sea and shorebird lineages diverged at least by the Late Cretaceous about 74 +/- 3 Ma (Campanian). It is clear that modern birds from at least the latest Cretaceous lived at the same time as archaic birds including Hesperornis, Ichthyornis, and the diverse Enantiornithiformes. Pterosaurs, which also coexisted with early crown birds, show notable changes through the Late Cretaceous. There was a decrease in taxonomic diversity, and small- to medium-sized species disappeared well before the end of the Cretaceous. A simple reading of the fossil record might suggest competitive interactions with birds, but much more needs to be understood about pterosaur life histories. Additional fossils and molecular data are still required to help understand the role of biotic interactions in the evolution of Late Cretaceous birds and thus to test that the mechanisms of microevolution are sufficient to explain macroevolution.

Discovery of an ornithurine bird and its implication for Early Cretaceous avian radiation.

An ornithurine bird, Hongshanornis longicresta gen. et sp. nov., represented by a nearly complete and articulated skeleton in full plumage, has been recovered from the lacustrine deposits of the Lower Cretaceous Jehol Group in Inner Mongolia, northeast China. The bird had completely reduced teeth and possessed a beak in both the upper and lower jaws, representing the earliest known beaked ornithurine. The preservation of a predentary bone confirms that this structure is not unique to ornithischian dinosaurs but was common in early ornithurine birds. This small bird had a strong flying capability with a low aspect ratio wing. It was probably a wader, feeding in shallow water or marshes. This find confirms that the aquatic environment had played a key role in the origin and early radiation of ornithurines, one branch of which eventually gave rise to extant birds near the Cretaceous/Tertiary boundary. This discovery provides important information not only for studying the origin and early evolution of ornithurines but also for understanding the differentiation in morphology, body size, and diet of the Early Cretaceous birds.

A new fossil bird from the Early Cretaceous of Gansu Province, northwestern China

We report on the discovery of an Early Cretaceous bird from northwestern Gansu Province, in northwestern China. Represented by a nearly complete left wing and shoulder girdle the size of a rock dove, the new bird was quarried from laminated yellowish mudstones of the Xiagou Formation (Xinminpu Group) near Changma, in the Jiuquan area. These deposits have previously yielded the only known specimen of Gansus yumenensis, a basal ornithuromorph represented by the distal half of a hind limb with long and slender digits. Several derived characters of the new occurrence supports its allocation within Enantiornithes: (1) a convex lateral margin of the coracoid, (2) a minor metacarpal that projects distally more than the major metacarpal and (3) a proximal phalanx of the major digit longer than the intermediate (second) phalanx. The general proportions of the wing suggest it was a flier comparable to most other known enantiornithine birds. Although, direct comparisons between the new fossil and Gansus are not possible, phylogenetic based inferences supports their placement into two different clades. While the new fossil falls definitively within the enantiornithines, G. Yumenensis falls within the ornithuromorphs. The new occurrence thus adds to the taxonomic diversity of Early Cretaceous birds from Gansu Province in particular and central Asia in general.

Leg feathers in an Early Cretaceous bird

Here we describe a fossil of an enantiornithine bird from the Early Cretaceous period in China that has substantial plumage feathers attached to its upper leg (tibiotarsus). The discovery could be important in view of the relative length and aerodynamic features of these leg feathers compared with those of the small 'four-winged' gliding dinosaur Microraptor and of the earliest known bird, Archaeopteryx. They may be remnants of earlier long, aerodynamic leg feathers, in keeping with the hypothesis that birds went through a four-winged stage during the evolution of flight.

The origin and early evolution of birds: discoveries, disputes, and perspectives from fossil evidence.

The study of the origin and early evolution of birds has never produced as much excitement and public attention as in the past decade. Well preserved and abundant new fossils of birds and dinosaurs have provided unprecedented new evidence on the dinosaurian origin of birds, the arboreal origin of avian flight, and the origin of feathers prior to flapping flight. The Mesozoic avian assemblage mainly comprises two major lineages: the prevalent extinct group Enantiornithes, and the Ornithurae, which gave rise to all modern birds, as well as several more basal taxa. Cretaceous birds radiated into various paleoecological niches that included fish- and seed-eating. Significant size and morphological differences and variation in flight capabilities, ranging from gliding to powerful flight among early birds, highlight the diversification of birds in the Early Cretaceous. There is little evidence, however, to support a Mesozoic origin of modern avian groups. Controversy and debate, nevertheless, surround many of these findings, and more details are needed to give a better appreciation of the significance of these new discoveries.

The dinosaurian origin of feathers: perspectives from dolphin (Cetacea) collagen fibers.

The early origin of birds is a hotly disputed debate and may be broadly framed as a conflict between paleontologists and ornithologists. The paleontological emphasis has shifted from Archaeopteryx and its origins to recent finds of Cretaceous birds and "feathered" dinosaurs from China. The identification of alleged feathers has, however, relied principally on the visual image. Some workers have interpreted these integumentary structures as collagen fibers. To test the latter hypothesis, using light microscopy, collagen from the hypodermis (blubber) and subdermal connective tissue sheath was examined from a dolphin that had been buried for a year as part of an experiment. Within the blubber, toward the central thicker parts of the material, the collagen fibers had compacted and the three-dimensional latticework of normal blubber had more or less collapsed. Chromatographic analysis of the blubber revealed pronounced oxidation of the unsaturated lipids, probably accounting for the collapse of the latticework. Fibers normally bound together in bundles became separated into individual fibers or smaller bundles by degradation of the glue-like substance binding them together. These degraded collagen fibers show, in many instances, feather-like patterns, strikingly reminiscent of many of those identified as either "protofeathers" or "modern" feathers in dromaeosaurid dinosaurs. The findings throw serious doubt on the virtually complete reliance on visual image by supporters of the feathered dinosaur thesis and emphasize the need for more rigorous methods of identification using modern feathers as a frame of reference. Since collagen is the main fiber type found in most supporting tissues, the results have wide implications regarding the degradation and fossilization of vertebrate integument, such as that of the ichthyosaurs, dinosaurs and birds.

Faux et usage de faux

Forgeries and use of forgery. Gould’s observations on the falsified fossils of Morocco are completed by Cambrian and Mesozoic examples. The methods of falsification are briefly described. Gould has compared this mystification to the Beringer “Lügensteine” of the XVIIIth century. Was the Piltdown Man half human and half-ape? Was Teilhard de Chardin an accomplice in this hoax? European Paleozoic fossils were said to have been fraudulently introduced in Deprat's field localities. Accused and later rehabilitated, the question of the real origin of the fossils is still open: who is guilty? Gupta has conceived an improbable Himalayan geology, with fossils of other countries, determined with confidence by specialists. Frontals, wearing spiral horns of an unknown bovid, Pseudonovibos, were in fact falsified horns of ordinary domestic bos (Indochina). The mediatic series about Archaeoraptor, the first flying dinosaur, ended when it was recognised that the specimen is a composite, a chimera between a carnivorous dinosaur and Cretaceous bird. To cite this article: F. Debrenne, C. R. Palevol 2 (2003).

The birds from Las Hoyas.

Information on the first steps of the avian evolutionary history has dramatically increased during the last few years. The fossil record provides a general view of the morphological changes of the avian flight apparatus from nonvolant ancestors (non-avian theropod dinosaurs) to the first derived fliers of the Early Cretaceous. The Las Hoyas bird record includes three genera: Iberomesornis, Concornis and Eoalulavis. This fossil material has yielded information about the early avian evolutionary history. These Early Cretaceous birds (some 120 Myr old) had a wingbeat cycle and breathing devices similar to those of extant birds. The function of the rectricial fan was also similar. In the evolutionary transition from cursorial ancestors to derived fliers it is possible to verify a trend to increase lift. Primitive wing aspect ratio morphotypes were elliptical ones, other derived morphotypes appeared, for example, in the Neornithes (extant birds). Some primitive fliers, like the Las Hoyas genus Eoalulavis, had an alula (feathers attached to the first digit of the hand) similar to that of present day birds, indicating braking and manoeuvring skills similar to those of their extant relatives. Primitive avian life habits are poorly understood. Some evidence from the Las Hoyas bird record indicates that Early Cretaceous birds were present in the trophic chains.

A new and primitive enantiornithine bird from the Early Cretaceous of China

ABSTRACT A new Early Cretaceous enantiornithine bird, Eocathayornis walkeri, gen. et sp. nov. is reported from Liaoning, northeast China. It is about the size of Cathayornis but is more primitive. Teeth are present on the jaws. Claws are retained on three wing digits, but that of the minor digit is reduced. The width of the radius is nearly three-fourths that of the ulna. The sternum is relatively short, with a pair of long caudo-lateral processes and a low and caudally distributed keel. The coracoid is strut-like and caudally concave, typical of enantiornithine birds. The advanced features of the scapula and the wing suggest a powerful flapping flight capability. This bird is referred to the family Cathayornidae based on a few shared derived characters with Cathayornis.

Largest bird from the Early Cretaceous and its implications for the earliest avian ecological diversification.

With only one known exception, early Cretaceous birds were smaller than their closest theropod dinosaur relatives. Here we report on a new bird from the Early Cretaceous feathered-dinosaur-bearing continental deposits of Liaoning, northeast China, which is not only larger than Archaeopteryx but is nearly twice as large as the basal dromaeosaur Microraptor. The new taxon, Sapeornis chaoyangensis gen. et sp. nov., has a more basal phylogenetic position than all other birds except for Archaeopteryx. Its exceptionally long forelimbs, well-developed deltoid crest of the humerus, proximally fused metacarpals, relatively short hindlimbs and short pygo-style indicate powerful soaring capability and further suggest that by the Early Cretaceous ecological diversification of early birds was greater than previously assumed. Electronic supplementary material to this paper can be obtained by using the Springer LINK server located at http://dx.doi.org/10.1007/s00114-001-0276-9.

An archaic bird (Enantiornithes) from the Upper Cretaceous of Provence (southern France)

A tibiotarsus of an archaic bird from the Upper Cretaceous of Fox-Amphoux (Var, southern France) is described and referred to the Enantiornithes. Taken together with other recent discoveries of Late Cretaceous birds from France, this find suggests that at the end of the Cretaceous, the European avifauna was dominated by archaic forms.

The Fossil Record of Cretaceous Tetrapods

Abstract The fossil record of the Cretaceous is critical for understanding the evolution of modern tetrapods. Using a measure of relative completeness of the fossil record—the Simple Completeness Metric (SCM)—quality of the fossil record and diversity during the Cretaceous appear to be closely related, suggesting an artifactual component. The SCM calculations also show that knowledge of the fossil record has improved in the last ten years. Recent proposals that modern orders of birds and mammals originated early in the Cretaceous are rendered unlikely by four arguments: (1) the SCM calculations indicate that the fossil record of Cretaceous birds and mammals is relatively good; (2) it is unlikely that all modern orders, independently, would have remained cryptic throughout the Cretaceous; (3) control samples of exquisitely preserved tiny Cretaceous tetrapods lack any specimens of modern groups of birds and mammals; and (4) the suggestion that the undiscovered ancestors of modern groups are to be found in u...

Liaoxiornis delicatus gen. et sp. nov., the smallest Mesozoic bird

Recently, a very small and complete bird specimen was collected from the Confuciu-sorn/s-bearing Yixian Formation. This finding represents a new kind of Mesozoic bird, named Liaoxiornis delicatus. It is characterized by a short skull with teeth, a long neck and a very small sternum with only posterior process; the humeral head is not internally curved, and the hindlimbs are longer than the forelimbs. Liaoxiornis delicatus is not only much smaller than Confuciusornis, but also smaller than Cathayornis and other early Cretaceous birds. It is the smallest bird known from Mesozoic deposit. Liaoxiornis provides new evidence indicating that the early adaptive radiation of birds is complicated.

Keratin immunoreactivity in the Late Cretaceous bird Rahonavis ostromi

ABSTRACT Immunohistochemical studies, supported by additional lines of evidence, suggest that original proteinaceous components of keratin claw sheath material may be preserved in the pedal ungual phalanx associated with the primitive bird, Rahonavis ostromi, from the Late Cretaceous of Madagascar. This conclusion is based upon immunohistochemical analyses, and supported by brightfield, transmission, and scanning electron microscopy, mass spectrometry, and x-ray photoelectron spectroscopy. Although keratinous structures such as hair, nails, claws, scales and feathers have been identified in the fossil record, these identifications were based on morphological similarity rather than molecular analyses. Chemical or immunological evidence for the survival of keratin has not previously been established in fossils older than ~33,000 BP. This study demonstrates immunological staining and amino acid composition consistent with the presence of fragments of beta keratin, a protein family unique to reptiles and birds, in the specimen of Rahonavis ostromi.

A lower jaw from a Cretaceous parrot

All known Cretaceous bird fossils representing modern higher taxa are from the aquatic groups Anseriformes1,3, Gaviiformes4,5, Procellariiformes1 and Charadriiformes1,6. Here I describe a toothless avian dentary symphysis (fused jawbone) from the latest Cretaceous of Wyoming, United States. This symphysis appears to represent the oldest known parrot and is, to my knowledge, the first known fossil of a ‘terrestrial’ modern bird group from the Cretaceous. The existence of this fossil supports the hypothesis, based on molecular divergence data7,8, that most or all of the major modern bird groups were present in the Cretaceous.

Bird, Dinosaur Link

Ann Gibbons's Research News article “Missing link ties birds, dinosaurs” about the discovery of the unusual Cretaceous bird Rahonavis (nee Rahona) (20 Mar., [p. 1851][1]) includes commentary from two scientists who doubt that the forelimbs and hindlimbs belong to a single animal. One of the authors of the original report (20 Mar., [p. 1915][2]), Catherine A. Forster, is quoted in response that a source from two different animals cannot be ruled out, although “she contends that the hind limbs are clearly bird legs.” In fact, the study itself shows a stronger test of this hypothesis (Forster et al.'s note 22, [p. 1915][2]) that was not reflected in the News article. Phylogenetic analyses were run twice, once including the questioned forelimb material, which was found “next to or touching the hind portion of the skeleton,” and once without it. In both cases the phylogenetic position of Rahonavis was the same, clustering with Unenlagia plus Archaeopteryx and other birds. This shows clearly that the fore and hind limbs belong to the same animal, unless they represent two different kinds of animals with exactly the same evolutionary relationships to other groups (which would amount to nearly the same thing). Critics of the dinosaurian ancestry of birds are quoted as characterizing Rahonavis as “a little dinosaur hindquarter, with a bird's forelimbs,” or as “another dinosaur trying to hit it big as a bird.” The kinds of analysis that Forster et al . carried out indicate that these critics are closer to the mark than they would like to be, because the overwhelming evidence indicates that birds did indeed evolve from dinosaurs ([2][3]). As evolutionary theory would predict, the most basal birds show a mosaic of retained theropod features and new avian characters. 1. 1. K. Padian, 2. L. Chiappe , Biol. Rev. 73, 1 (1998). [OpenUrl][4][CrossRef][5][GeoRef][6] 2. [↵][7]1. L. Dingus, 2. T. Rowe , The Mistaken Extinction (Prentice-Hall, New York, 1997). [1]: /lookup/doi/10.1126/science.279.5358.1851 [2]: /lookup/doi/10.1126/science.279.5358.1915 [3]: #ref-2 [4]: {openurl}?query=rft.jtitle%253DBiological%2BReviews%2B%2528Cambridge%253B%2BPrint%2529%26rft.stitle%253DBiological%2BReviews%2B%2528Cambridge%253B%2BPrint%2529%26rft.volume%253D73%26rft.issue%253D1%26rft.spage%253D1%26rft.epage%253D42%26rft.atitle%253DThe%2Borigin%2Band%2Bearly%2Bevolution%2Bof%2Bbirds%26rft_id%253Dinfo%253Adoi%252F10.1017%252FS0006323197005100%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [5]: /lookup/external-ref?access_num=10.1017/S0006323197005100&link_type=DOI [6]: /lookup/external-ref?access_num=1998038706&link_type=GEOREF [7]: #xref-ref-2-1 View reference 2 in text

The origin and early evolution of birds

ABSTRACTBirds 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’.