Enantiornithes
Encyclopedia
Enantiornithes is an extinct group of primitive bird
s. They were the most abundant and diverse avialans
of the Mesozoic
. Almost all retained teeth and clawed fingers on each wing, but otherwise looked much like modern birds externally. Over 50 species of Enantiornithines have been named, but some names represent only single bones, so it is likely that not all are valid. Enantiornithine birds went extinct at the K-Pg boundary, along with hesperornithine birds
and all other non-avian dinosaur
s, and many other mostly reptilian life forms. Enantiornithines are thought to have left no living descendants.
Most researchers place Enantiornithines in Aves, but those that use the more restrictive crown group
definition of Aves put them in the more inclusive Avialae
, specifically, as members of the clade Ornithothoraces
. Enantiornithines were more advanced than Archaeopteryx
or Confuciusornis
, but in several respects more primitive than all modern birds
(Neornithes), perhaps following an intermediate evolutionary path. Due to the primitive features, some early studies placed Enantiornithes with Archaeopteryx
in the paraphyletic grouping Sauriurae
, but few researchers still do so.
A consensus of scientific analyses indicates that Enantiornithes is one of two major groups of birds within the Ornithothoraces. The other group is the Ornithurae
, which includes all living birds as a subset. This means that Enantiornithines are a successful branch of bird evolution, but one that diversified entirely separately from the lineage leading to modern birds. The consensus on the reality of this basic two-way split has never been universally accepted and has been challenged by some studies, and that it is possible that enantiornithines may actually represent successive outgroups of the lineage leading to modern birds.
period of what is now Argentina
. Since the 1990s, more complete enantiornithines were discovered and it was demonstrated that a few previously described birds (e.g. Iberomesornis
, Cathayornis
, Sinornis) had enantiornithine features.
"Enantiornithes" means "opposite birds", from Ancient Greek
einantios (ἐνάντιος) "opposite" + ornithes (όρνιθες) "birds" . The name was coined by Walker in his landmark paper which established the group. In his paper, Walker explained what he meant by "opposite":
This refers to an anatomical feature – the articulation of the shoulder
bones – which has a concave-convex socket joint that is the reverse of that of modern birds. Specifically, in enantiornithines, the facet where the scapula (shoulder blade) meets the coracoid (the primary bone of the shoulder girdle in vertebrates other than mammals) is a convex knob and the corresponding point on the shoulder blade is concave and dish-shaped. In modern birds, the way the joint articulates is reversed.
Walker was not clear on his reasons for giving this name in the Etymology section of his paper, and this ambiguity led to some confusion among later researchers. For example, Alan Feduccia
stated in 1996:
Feduccia's point about the tarsometatarsus
(the combined upper foot and ankle bone) is correct, but Walker did not use this reasoning in his original paper. Walker never described the fusion of the tarsometatarsus as opposite, but rather as "Only partial". Also, it is not certain that enantiornithines had triosseal canals, since no fossil preserves this feature.
in Cuenca
(Spain) and the Yixian Formation
in Liaoning
(PRC
). They have been found in both inland and marine sediments, suggesting that they were an ecologically diverse group. Enantiornithine fossils appear to include waders, swimmers, fish-catchers, and raptors. The smallest are described as sparrow
-sized, but some were much larger, such as Avisaurus
which had an estimated wingspan of 1.2 meters (4 ft).
, they retained the postorbital
bone and a small premaxilla, and most species had toothy jaws rather than toothless beaks. Only a few species, such as Gobipteryx minuta, were fully toothless.
. While most enantiornithines retained claws on at least some of the fingers, many species had shortened hands, a highly mobile shoulder anatomy, and other proportional changes in the wing bones similar to modern birds. Enantiornithines also had alula
s, or "bastard wings", a small forward-pointing arrangement of feathers on the first digit that granted higher maneuverability in the air and aided precie landing.
As a very large group of birds, enantiornithines displayed a diversity of different body plans based on differences in ecology and feeding, reflected in an equal diversity of wing forms, many paralleling adaptions to different lifestyles seen in modern birds.
One enantiornithine fossil shows wing-like feather tufts on its legs, similar to Archaeopteryx
. Leg feathers are also reminiscent of the four-winged dinosaur Microraptor
, however, in the enantiornithine differ from the feathers are shorter, more disorganized (do not clearly form a wing) and only extend down to the ankle rather than along the foot.
Clarke et al. (2006) surveyed all enantiornithine fossils then known and concluded that none had preserved tail feathers that formed a lift-generating fan, as in modern birds. They found that all birds outside of the ornithurae
with preserved tail feathers had only short coverts or elongated paired tail plumes. Thus, they suggested that the development of the pygostyle
in enantiornithes must have been a function of tail shortening, not the development of a modern tail feather anatomy. An ornithurine bird, Yixianornis
, was reported by the authors as the earliest bird with a fan of tail feathers. However, in 2009, an enantiornithine called Shanweiniao
was reported with four long tail feathers that overlapped each other, possibly forming a lift-generating surface similar to the tail fans of modern birds.
, South America
, Europe
, Asia
, and Australia
. Known fossils attributable to this group are exclusively Cretaceous
and it is believed that enantiornithines became extinct at the same time as their non-avian dinosaur
relatives. One biogeographic study in the 1990s suggested that the distribution of enantiornithines implies a Middle Jurassic
origin for the clade, but this theory has not been widely accepted by paleoornithologists; a Late Jurassic/Early Cretaceous origin is more in line with the fossil record. The earliest known enantiornithines are from the Early Cretaceous
) of Spain
(e.g. Noguerornis
, a basal genus) and China
(e.g. Protopteryx
) and the latest from the Late Cretaceous
of North and South America (e.g. Avisaurus
). The widespread occurrence suggests that the Enantiornithes were able to cross oceans on their own power; they are the first bird lineage with a global distribution. Some might thus even have been migratory
, but given the markedly warmer climate
of the Mesozoic
and the fact that the known Enantiornithes are from regions that were subtropical if not tropical at that time, it seems unlikely that the known diversity of these birds contains long-distance migrants.
Given the wide diversity of skull shape among enantiornithines, many different dietary specializations must have been present among the group. Some forms, like Shenqiornis
, had large, robust jaws suitable for eating hard-shelled invertebrates. In longipterygids
, the snouts were long and thin with teeth restricted to the tip of the jaws, and they were likely mud-probers (small-toothed species) and fishers (large-toothed species). The short, blunt teeth of Pengornis
were likely used to feed on soft-bodied arthropods.
A few specimens preserve actual stomach contents. Unfortunately, none of these preserve the skull, so direct correlation between their known diet and snout/tooth shape cannot be made. Eoalulavis
was found to have the remains of exoskeleton
s of aquatic crustacean
s preserved in its digestive tract., and Enantiophoenix
preserves corpuscles of amber among the fossilized bones, suggesting that this animal fed on tree sap, much like modern sapsucker
s and other birds. The sap would have fossilized and become amber.
or small theropod dinosaur. This was the first evidence that Mesozoic
birds were prey animals, and that some Mesozoic ornithodires regurgitated pellets like owls do today.
, embryo
s, and hatchling
s. An enantiornithine embryo, still curled in its egg, has been reported from the Yixian Formation
. Juvenile specimens can be identified by a combination of factors: rough texture of their bone tips indicating portions which were still made of cartilage at the time of death, relatively small breastbones, large skulls and eyes, and bones which had not yet fused to one another. Some hatchling specimens have been given formal names, including "Liaoxiornis delicatus"; however, Luis Chiappe and colleagues considered the practice of naming new species based on juveniles detrimental to the study of enantionrithines, because it is nearly impossible to determine which adult species a given juvenile specimen belongs to, making any species with a hatchling holotype a nomen dubium
.
Together with the hatchlings assigned to Gobipteryx
, these finds demonstrate that enantiornithine hatchlings had the skeletal ossification, well-developed wing feathers and the large brain which correlate with precocial
or superprecocial
patterns of development in birds of today. Thus, at least some enantiornithine birds probably hatched from the egg substantially developed and ready to run, forage, and possibly even fly in a just a few days. This, together with the fact that the most ancient lineages of modern birds – paleognaths and Galloanserae – are precocial, suggests that the precocial condition is plesiomorphic and was common among Cretaceous birds.
Analyses of enantiornithine bone histology have been conducted to determine the growth rates of the animals. One recent study of Concornis
bones shows a growth pattern different from modern birds: Although growth was rapid for some weeks after hatching – probably until fledging – this fairly small species did not reach adult size for a long time, probably several years. Another study supports that growth to adult size was slow, as it is in living precocial birds. Altricial
birds on the other hand are known to reach adult size quickly thanks to lavish parental feeding. Still other analyses have interpreted the bone histology to indicate that enantiornithines may not have had fully avian endotherm
y, instead having an intermediate metabolic rate.
Cau and Arduini, 2008
O'Connor, Gao and Chiappe, 2010
You et al., 2010
Enantiornithine classification and taxonomy has historically been complicated by a number of factors. In 2010, Mesozoic bird paleontologists Jingmai O'Connor and Gareth Dyke outlined a number of criticisms against the prevailing practices of scientists failing to describe many specimens in enough detail for others to evaluate thoroughly. Some species have been described based on specimens which are held in private collections, making further study or review of previous findings impossible. Because it is often unfeasible for other scientists to study each specimen in person given the worldwide distribution of the Enantiornithes, and due to the many uninformative descriptions which have been published on possibly important specimens, many of these specimens become "functional nomina dubia
". Furthermore, many species have been named based on extremely fragmentary specimens, which would not be very informative scientifically even if they were described sufficiently. Over one-third of all named enantiornithine taxa are based on only a fragment of a single bone. O'Connor and Dyke argued that while these specimens can help expand knowledge of the time span or geographic range of the Enantiornithes and it is important to describe them, naming such specimens is "unjustifiable".
or Ornithuromorpha depending on the taxonomic authority, and together they form a clade
called Ornithothoraces
. Most phylogenetic studies have recovered Enantiornithes as a monophyletic group distinct from the modern birds and their closest relatives. The 2002 phylogenetic analysis by Clarke and Norell, though, reduced the number of enantiornithine autapomorphies to just four.
Enantiornithine systematics are highly provisional. The version used here, although based on many sources, is only tentative, and in need of revision in light of abundant new fossil discoveries. What appears fairly certain by now is that there were subdivisions within Enantiornithes possibly including some minor basal lineages in addition to the more apomorphic Euenantiornithes. The details of the interrelationship of all these lineages, indeed the validity of most, is disputed, although the Avisauridae, for one example, seem likely to constitute a valid group. Phylogenetic taxonomists have hitherto been very reluctant to suggest delimitations of enantiornithine clades.
Sometimes included in the Enantiornithes are the following taxa:
The three taxa "Jibeinia
", "Vescornis
", and "Hebeiornis
", may be synonyms. (See the three articles for details on the confusion). If so, "Jibeinia
" was published in 1997, "Vescornis
"was described in 2004, and "Hebeiornis
"was published in 1999 but it may not have been an adequate description. Therefore, if the three names truly do describe the same Genus
, the senior synonym of the three would be "Jibeinia
". Unfortunately, Dr. Hou reported the holotype
of Jibeinia
lost in 2001.
The Late Cretaceous taxon "Cerebavis" is based on an endocranial cast and while this is not diagnostic, it is different from modern birds and as far as can be told from Ornithurae in general.
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
s. They were the most abundant and diverse avialans
Avialae
Avialae is a clade of dinosaurs containing their only living representatives, birds , and the most immediate extinct relatives of birds.-Competing definitions:...
of the Mesozoic
Mesozoic
The Mesozoic era is an interval of geological time from about 250 million years ago to about 65 million years ago. It is often referred to as the age of reptiles because reptiles, namely dinosaurs, were the dominant terrestrial and marine vertebrates of the time...
. Almost all retained teeth and clawed fingers on each wing, but otherwise looked much like modern birds externally. Over 50 species of Enantiornithines have been named, but some names represent only single bones, so it is likely that not all are valid. Enantiornithine birds went extinct at the K-Pg boundary, along with hesperornithine birds
Hesperornithes
Hesperornithes is an extinct and highly specialized clade of Cretaceous toothed birds. Hesperornithine birds, apparently limited to former aquatic habitats in the Northern Hemisphere, include genera such as Hesperornis, Parahesperornis, Baptornis, Enaliornis, and probably Potamornis, all...
and all other non-avian dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
s, and many other mostly reptilian life forms. Enantiornithines are thought to have left no living descendants.
Most researchers place Enantiornithines in Aves, but those that use the more restrictive crown group
Crown group
A crown group is a group consisting of living representatives, their ancestors back to the most recent common ancestor of that group, and all of that ancestor's descendants. The name was given by Willi Hennig, the formulator of phylogenetic systematics, as a way of classifying living organisms...
definition of Aves put them in the more inclusive Avialae
Avialae
Avialae is a clade of dinosaurs containing their only living representatives, birds , and the most immediate extinct relatives of birds.-Competing definitions:...
, specifically, as members of the clade Ornithothoraces
Ornithothoraces
Ornithothoraces is a clade of birds which includes all enantiornithines and modern birds .The name Ornithothoraces means "bird thoraxes". This refers to a modern, highly derived, anatomy of the thorax which gave the ornithothoracines superior flight capability compared to more primitive birds...
. Enantiornithines were more advanced than Archaeopteryx
Archaeopteryx
Archaeopteryx , sometimes referred to by its German name Urvogel , is a genus of theropod dinosaur that is closely related to birds. The name derives from the Ancient Greek meaning "ancient", and , meaning "feather" or "wing"...
or Confuciusornis
Confuciusornis
Confuciusornis is a genus of primitive crow-sized birds from the Early Cretaceous Yixian and Jiufotang Formations of China, dating from 125 to 120 million years ago...
, but in several respects more primitive than all modern birds
Modern birds
Modern birds are the most recent common ancestor of all living birds and all its descendants.Modern birds are characterised by feathers, a beak with no teeth , the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a lightweight but strong skeleton...
(Neornithes), perhaps following an intermediate evolutionary path. Due to the primitive features, some early studies placed Enantiornithes with Archaeopteryx
Archaeopteryx
Archaeopteryx , sometimes referred to by its German name Urvogel , is a genus of theropod dinosaur that is closely related to birds. The name derives from the Ancient Greek meaning "ancient", and , meaning "feather" or "wing"...
in the paraphyletic grouping Sauriurae
Sauriurae
Sauriurae is a now-deprecated subclass of birds created by Ernst Haeckel in 1866. It was intended to include Archaeopteryx and distinguish it from all other birds then known, which he grouped in the sister-group Ornithurae...
, but few researchers still do so.
A consensus of scientific analyses indicates that Enantiornithes is one of two major groups of birds within the Ornithothoraces. The other group is the Ornithurae
Ornithurae
Ornithurae is the name of a natural group which includes all modern birds as well as their extinct relatives with plough-shaped pygostyles, a bone at the end of the tail which allows the tail feathers to fan and retract....
, which includes all living birds as a subset. This means that Enantiornithines are a successful branch of bird evolution, but one that diversified entirely separately from the lineage leading to modern birds. The consensus on the reality of this basic two-way split has never been universally accepted and has been challenged by some studies, and that it is possible that enantiornithines may actually represent successive outgroups of the lineage leading to modern birds.
Discovery and naming
The first enantiornithines to be discovered were incorrectly referred to modern bird groups. They were first recognized as a distinct lineage by Cyril A. Walker, in 1981, based on some partial remains from the late CretaceousCretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
period of what is now Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
. Since the 1990s, more complete enantiornithines were discovered and it was demonstrated that a few previously described birds (e.g. Iberomesornis
Iberomesornis
Iberomesornis is a monotypic genus of enantiornithine bird of the Cretaceous of Spain.In 1985 the fossil of Iberomesornis was discovered by Armando Díaz Romeral in the Early Cretaceous Calizas de La Huérguina Formation at Las Hoyas, Cuenca Province, east central Spain, which dates to the late...
, Cathayornis
Cathayornis
Cathayornis is a genus of enantiornithine bird from the Jiufotang Formation of Liaoning, People's Republic of China and, in the case of the possible species C...
, Sinornis) had enantiornithine features.
"Enantiornithes" means "opposite birds", from Ancient Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...
einantios (ἐνάντιος) "opposite" + ornithes (όρνιθες) "birds" . The name was coined by Walker in his landmark paper which established the group. In his paper, Walker explained what he meant by "opposite":
"Perhaps the most fundamental and characteristic difference between the Enantiornithes and all other birds is in the nature of the articulation between the scapulaScapulaIn anatomy, the scapula , omo, or shoulder blade, is the bone that connects the humerus with the clavicle ....
[...] and the coracoid, where the 'normal' condition is completely reversed."
This refers to an anatomical feature – the articulation of the shoulder
Shoulder
The human shoulder is made up of three bones: the clavicle , the scapula , and the humerus as well as associated muscles, ligaments and tendons. The articulations between the bones of the shoulder make up the shoulder joints. The major joint of the shoulder is the glenohumeral joint, which...
bones – which has a concave-convex socket joint that is the reverse of that of modern birds. Specifically, in enantiornithines, the facet where the scapula (shoulder blade) meets the coracoid (the primary bone of the shoulder girdle in vertebrates other than mammals) is a convex knob and the corresponding point on the shoulder blade is concave and dish-shaped. In modern birds, the way the joint articulates is reversed.
Walker was not clear on his reasons for giving this name in the Etymology section of his paper, and this ambiguity led to some confusion among later researchers. For example, Alan Feduccia
Alan Feduccia
Alan Feduccia is a paleornithologist, specializing in the origins and phylogeny of birds. He is now Professor Emeritus at the University of North Carolina. Feduccia's principal authored works include two books, The Age of Birds and The Origin and Evolution of Birds, and numerous papers in various...
stated in 1996:
"The birds are so named because, among many distinctive features, there is a unique formation of the triosseal canal and the metatarsals are fused proximally to distally, the opposite of that in modern birds"
Feduccia's point about the tarsometatarsus
Tarsometatarsus
The tarsometatarsus is a bone that is found in the lower leg of certain tetrapods, namely birds.It is formed from the fusion of several bones found in other types of animals, and homologous to the mammalian tarsal and metatarsal bones...
(the combined upper foot and ankle bone) is correct, but Walker did not use this reasoning in his original paper. Walker never described the fusion of the tarsometatarsus as opposite, but rather as "Only partial". Also, it is not certain that enantiornithines had triosseal canals, since no fossil preserves this feature.
Description
Many enantiornithine fossils are found in highly fragmentary states, and some taxa are known only from a piece of a single bone. Particularly exquisite specimens that are complete, in full articulation and with soft tissue preservation are known from Las HoyasLas Hoyas
Las Hoyas is a Cretaceous Konservat-Lagerstätten located near the city of Cuenca, Spain.It is dated as Barremian , and is mostly known from its exquisitely preserved dinosaurs, especially enantiornithines.- Taphonomy :...
in Cuenca
Cuenca (province)
Cuenca is a province of central Spain, in the eastern part of the autonomous community of Castile-La Mancha.-Guide to the area:Located in a natural setting of beauty, the Old Town of Cuenca occupies a superb site between two river gorges. Famous are its 15th Century "hanging houses" , that appear...
(Spain) and the Yixian Formation
Yixian Formation
The Yixian Formation is a geological formation in Jinzhou, Liaoning, People's Republic of China, that spans 11 million years during the early Cretaceous period...
in Liaoning
Liaoning
' is a province of the People's Republic of China, located in the northeast of the country. Its one-character abbreviation is "辽" , a name taken from the Liao River that flows through the province. "Níng" means "peace"...
(PRC
People's Republic of China
China , officially the People's Republic of China , is the most populous country in the world, with over 1.3 billion citizens. Located in East Asia, the country covers approximately 9.6 million square kilometres...
). They have been found in both inland and marine sediments, suggesting that they were an ecologically diverse group. Enantiornithine fossils appear to include waders, swimmers, fish-catchers, and raptors. The smallest are described as sparrow
Sparrow
The sparrows are a family of small passerine birds, Passeridae. They are also known as true sparrows, or Old World sparrows, names also used for a genus of the family, Passer...
-sized, but some were much larger, such as Avisaurus
Avisaurus
Avisaurus is a genus of enantiornithine bird from the Late Cretaceous of North America.Two species are known; the type species A. archibaldi and A. gloriae...
which had an estimated wingspan of 1.2 meters (4 ft).
Skull
Given their wide range of habitats and diets, the skulls of enantiornithines varied considerably between species. Enantiornithine skulls combined a unique suite of primitive and advanced characteristics. As in more basal birds like ArchaeopteryxArchaeopteryx
Archaeopteryx , sometimes referred to by its German name Urvogel , is a genus of theropod dinosaur that is closely related to birds. The name derives from the Ancient Greek meaning "ancient", and , meaning "feather" or "wing"...
, they retained the postorbital
Postorbital
The postorbital is one of the bones in vertebrate skulls which forms a portion of the dermal skull roof and, sometimes, a ring about the orbit. Generally, it is located behind the postfrontal and posteriorly to the orbital fenestra. In some vertebrates, the postorbital is fused with the postfrontal...
bone and a small premaxilla, and most species had toothy jaws rather than toothless beaks. Only a few species, such as Gobipteryx minuta, were fully toothless.
Wing
The wings of enantiornithines were relatively advanced compared to basal birds like Archaeopteryx, and display some features related to flight similar to those found in he lineage leading to modern birds, the OrnithuraeOrnithurae
Ornithurae is the name of a natural group which includes all modern birds as well as their extinct relatives with plough-shaped pygostyles, a bone at the end of the tail which allows the tail feathers to fan and retract....
. While most enantiornithines retained claws on at least some of the fingers, many species had shortened hands, a highly mobile shoulder anatomy, and other proportional changes in the wing bones similar to modern birds. Enantiornithines also had alula
Alula
The alula, or bastard wing, is a small projection on the anterior edge of the wing of modern birds. The alula is the freely moving first digit, a bird's "thumb," and is typically covered with three to five small feathers, with the exact number depending on the species...
s, or "bastard wings", a small forward-pointing arrangement of feathers on the first digit that granted higher maneuverability in the air and aided precie landing.
As a very large group of birds, enantiornithines displayed a diversity of different body plans based on differences in ecology and feeding, reflected in an equal diversity of wing forms, many paralleling adaptions to different lifestyles seen in modern birds.
One enantiornithine fossil shows wing-like feather tufts on its legs, similar to Archaeopteryx
Archaeopteryx
Archaeopteryx , sometimes referred to by its German name Urvogel , is a genus of theropod dinosaur that is closely related to birds. The name derives from the Ancient Greek meaning "ancient", and , meaning "feather" or "wing"...
. Leg feathers are also reminiscent of the four-winged dinosaur Microraptor
Microraptor
Microraptor is a genus of small, four-winged dromaeosaurid dinosaurs. Numerous well-preserved fossil specimens have been recovered from Liaoning, China...
, however, in the enantiornithine differ from the feathers are shorter, more disorganized (do not clearly form a wing) and only extend down to the ankle rather than along the foot.
Tail
Ornithurae
Ornithurae is the name of a natural group which includes all modern birds as well as their extinct relatives with plough-shaped pygostyles, a bone at the end of the tail which allows the tail feathers to fan and retract....
with preserved tail feathers had only short coverts or elongated paired tail plumes. Thus, they suggested that the development of the pygostyle
Pygostyle
Pygostyle refers to a number of the final few caudal vertebrae fused into a single ossification, supporting the tail feathers and musculature. In modern birds, the rectrices attach to these....
in enantiornithes must have been a function of tail shortening, not the development of a modern tail feather anatomy. An ornithurine bird, Yixianornis
Yixianornis
Yixianornis is a bird genus from the early Cretaceous period. Its remains have been found in the Jiufotang Formation at Chaoyang dated to the early Aptian age, around 120 million years ago. Only one species, Yixianornis grabaui, is known at present...
, was reported by the authors as the earliest bird with a fan of tail feathers. However, in 2009, an enantiornithine called Shanweiniao
Shanweiniao
Shanweiniao is an extinct genus of long-beaked enantiornithine bird from Early Cretaceous China. One species is known, Shanweiniao cooperorum. There is one known fossil, a slab and counterslab. The fossil is in the collection of the Dalian Natural History Museum, and has accession number DNHM...
was reported with four long tail feathers that overlapped each other, possibly forming a lift-generating surface similar to the tail fans of modern birds.
Origin and range
Enantiornithines have been found in North AmericaNorth America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
, South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
, Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
, Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
, and Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
. Known fossils attributable to this group are exclusively Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
and it is believed that enantiornithines became extinct at the same time as their non-avian dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
relatives. One biogeographic study in the 1990s suggested that the distribution of enantiornithines implies a Middle Jurassic
Jurassic
The Jurassic is a geologic period and system that extends from about Mya to Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...
origin for the clade, but this theory has not been widely accepted by paleoornithologists; a Late Jurassic/Early Cretaceous origin is more in line with the fossil record. The earliest known enantiornithines are from the Early Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
) of Spain
Spain
Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...
(e.g. Noguerornis
Noguerornis
Noguerornis is a genus of enantiornithine bird related to Iberomesornis. It lived during the Early Cretaceous about 130 mya and is known from fossils found at El Montsec, Spain....
, a basal genus) and China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
(e.g. Protopteryx
Protopteryx
Protopteryx is an extinct genus of bird, perhaps an enantiornithine, from the Cretaceous in China. The type species is P. fengningensis...
) and the latest from the Late Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
of North and South America (e.g. Avisaurus
Avisaurus
Avisaurus is a genus of enantiornithine bird from the Late Cretaceous of North America.Two species are known; the type species A. archibaldi and A. gloriae...
). The widespread occurrence suggests that the Enantiornithes were able to cross oceans on their own power; they are the first bird lineage with a global distribution. Some might thus even have been migratory
Bird migration
Bird migration is the regular seasonal journey undertaken by many species of birds. Bird movements include those made in response to changes in food availability, habitat or weather. Sometimes, journeys are not termed "true migration" because they are irregular or in only one direction...
, but given the markedly warmer climate
Climate
Climate encompasses the statistics of temperature, humidity, atmospheric pressure, wind, rainfall, atmospheric particle count and other meteorological elemental measurements in a given region over long periods...
of the Mesozoic
Mesozoic
The Mesozoic era is an interval of geological time from about 250 million years ago to about 65 million years ago. It is often referred to as the age of reptiles because reptiles, namely dinosaurs, were the dominant terrestrial and marine vertebrates of the time...
and the fact that the known Enantiornithes are from regions that were subtropical if not tropical at that time, it seems unlikely that the known diversity of these birds contains long-distance migrants.
Diet
Shenqiornis
Shenqiornis is a genus of enantiornithine . It was found in the Qiaotou member of the Huajiying Formation of Hebei Province, China, and is therefore of uncertain age. The Qiaotou Member may correlate with the more well-known Early Cretaceous Yixian Formation, and so probably dates to around 122 Ma...
, had large, robust jaws suitable for eating hard-shelled invertebrates. In longipterygids
Longipterygidae
Longipterygidae is a family of early enantiornithine birds from the early Cretaceous Period of China. All known specimens come from the Jiufotang Formation and Yixian Formation, dating to the early Aptian age, 122-120 million years ago.-Description:...
, the snouts were long and thin with teeth restricted to the tip of the jaws, and they were likely mud-probers (small-toothed species) and fishers (large-toothed species). The short, blunt teeth of Pengornis
Pengornis
Pengornis is the largest known enantiornithine bird from the Early Cretaceous of northeast China.the name Pengornis derives from "Peng", which refers to a mythological bird from Chinese folklore, and "-ornis", which means bird in Greek....
were likely used to feed on soft-bodied arthropods.
A few specimens preserve actual stomach contents. Unfortunately, none of these preserve the skull, so direct correlation between their known diet and snout/tooth shape cannot be made. Eoalulavis
Eoalulavis
Eoalulavis was an enantiornithine bird. It lived during the Aptian in the Early Cretaceous, about 115 mya and is known from fossils found at Las Hoyas, Spain...
was found to have the remains of exoskeleton
Exoskeleton
An exoskeleton is the external skeleton that supports and protects an animal's body, in contrast to the internal skeleton of, for example, a human. In popular usage, some of the larger kinds of exoskeletons are known as "shells". Examples of exoskeleton animals include insects such as grasshoppers...
s of aquatic crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s preserved in its digestive tract., and Enantiophoenix
Enantiophoenix
Enantiophoenix is a genus of enantiornithine bird. Fossil remains were recovered from Lebanon....
preserves corpuscles of amber among the fossilized bones, suggesting that this animal fed on tree sap, much like modern sapsucker
Sapsucker
The Sapsuckers form the genus Sphyrapicus within the woodpecker family Picidae. All are found in North America.As their name implies, sapsuckers feed primarily on the sap of trees, moving among different tree and shrub species on a seasonal basis...
s and other birds. The sap would have fossilized and become amber.
Predation
A specimen from Las Hoyas reported by Sanz et al. in 2001 includes the remains of four hatchling enantiornithine skeletons of three different species. They are substantially complete, very tightly associated, and show surface pitting of the bones that indicates partial digestion. The authors concluded that this association was a regurgitated pellet and, from the details of the digestion and the size, that the hatchlings were swallowed whole by a pterosaurPterosaur
Pterosaurs were flying reptiles of the clade or order Pterosauria. They existed from the late Triassic to the end of the Cretaceous Period . Pterosaurs are the earliest vertebrates known to have evolved powered flight...
or small theropod dinosaur. This was the first evidence that Mesozoic
Mesozoic
The Mesozoic era is an interval of geological time from about 250 million years ago to about 65 million years ago. It is often referred to as the age of reptiles because reptiles, namely dinosaurs, were the dominant terrestrial and marine vertebrates of the time...
birds were prey animals, and that some Mesozoic ornithodires regurgitated pellets like owls do today.
Life history
Described enantiornithine fossils include eggsEgg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
, embryo
Embryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...
s, and hatchling
Hatchling
In oviparous biology, a hatchling is the newborn of animals that develop and emerge from within hard-shell eggs. The offspring of birds are often hatched naked and with their eyes closed. The hatchling relies totally on its parents for feeding and warmth. Hatchlings precede nestlings in the chick's...
s. An enantiornithine embryo, still curled in its egg, has been reported from the Yixian Formation
Yixian Formation
The Yixian Formation is a geological formation in Jinzhou, Liaoning, People's Republic of China, that spans 11 million years during the early Cretaceous period...
. Juvenile specimens can be identified by a combination of factors: rough texture of their bone tips indicating portions which were still made of cartilage at the time of death, relatively small breastbones, large skulls and eyes, and bones which had not yet fused to one another. Some hatchling specimens have been given formal names, including "Liaoxiornis delicatus"; however, Luis Chiappe and colleagues considered the practice of naming new species based on juveniles detrimental to the study of enantionrithines, because it is nearly impossible to determine which adult species a given juvenile specimen belongs to, making any species with a hatchling holotype a nomen dubium
Nomen dubium
In zoological nomenclature, a nomen dubium is a scientific name that is of unknown or doubtful application...
.
Together with the hatchlings assigned to Gobipteryx
Gobipteryx
Gobipteryx is the name given to a genus of enantiornithine bird from the Late Cretaceous Period. Its fossils were found in the Barun Goyot Formation in the Gobi Desert, Mongolia and first described in 1976 from two fragmentary skulls...
, these finds demonstrate that enantiornithine hatchlings had the skeletal ossification, well-developed wing feathers and the large brain which correlate with precocial
Precocial
In biology, the term precocial refers to species in which the young are relatively mature and mobile from the moment of birth or hatching. The opposite developmental strategy is called "altricial," where the young are born or hatched helpless. Extremely precocial species may be called...
or superprecocial
Superprecocial
The term superprecocial refers to a level of physical maturity and capability in young animals that is most extreme. Examples are the Megapode birds, which have full flight feathers and which, in some species, can fly on the same day they hatch from their eggs...
patterns of development in birds of today. Thus, at least some enantiornithine birds probably hatched from the egg substantially developed and ready to run, forage, and possibly even fly in a just a few days. This, together with the fact that the most ancient lineages of modern birds – paleognaths and Galloanserae – are precocial, suggests that the precocial condition is plesiomorphic and was common among Cretaceous birds.
Analyses of enantiornithine bone histology have been conducted to determine the growth rates of the animals. One recent study of Concornis
Concornis
Concornis was an enantiornithine bird. It lived during the Early Cretaceous, in the late Barremian stage or about 127-125 million years ago, and its remains are known from the Calizas de La Huérguina Formation at Las Hoyas, Cuenca province, Spain...
bones shows a growth pattern different from modern birds: Although growth was rapid for some weeks after hatching – probably until fledging – this fairly small species did not reach adult size for a long time, probably several years. Another study supports that growth to adult size was slow, as it is in living precocial birds. Altricial
Altricial
Altricial, meaning "requiring nourishment", refers to a pattern of growth and development in organisms which are incapable of moving around on their own soon after hatching or being born...
birds on the other hand are known to reach adult size quickly thanks to lavish parental feeding. Still other analyses have interpreted the bone histology to indicate that enantiornithines may not have had fully avian endotherm
Endotherm
An endotherm is an organism that produces heat through internal means, such as muscle shivering or increasing its metabolism...
y, instead having an intermediate metabolic rate.
Classification
Enantiornithine classification and taxonomy has historically been complicated by a number of factors. In 2010, Mesozoic bird paleontologists Jingmai O'Connor and Gareth Dyke outlined a number of criticisms against the prevailing practices of scientists failing to describe many specimens in enough detail for others to evaluate thoroughly. Some species have been described based on specimens which are held in private collections, making further study or review of previous findings impossible. Because it is often unfeasible for other scientists to study each specimen in person given the worldwide distribution of the Enantiornithes, and due to the many uninformative descriptions which have been published on possibly important specimens, many of these specimens become "functional nomina dubia
Nomen dubium
In zoological nomenclature, a nomen dubium is a scientific name that is of unknown or doubtful application...
". Furthermore, many species have been named based on extremely fragmentary specimens, which would not be very informative scientifically even if they were described sufficiently. Over one-third of all named enantiornithine taxa are based on only a fragment of a single bone. O'Connor and Dyke argued that while these specimens can help expand knowledge of the time span or geographic range of the Enantiornithes and it is important to describe them, naming such specimens is "unjustifiable".
Phylogeny
Enantiornithes is the sister group to OrnithuraeOrnithurae
Ornithurae is the name of a natural group which includes all modern birds as well as their extinct relatives with plough-shaped pygostyles, a bone at the end of the tail which allows the tail feathers to fan and retract....
or Ornithuromorpha depending on the taxonomic authority, and together they form a clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
called Ornithothoraces
Ornithothoraces
Ornithothoraces is a clade of birds which includes all enantiornithines and modern birds .The name Ornithothoraces means "bird thoraxes". This refers to a modern, highly derived, anatomy of the thorax which gave the ornithothoracines superior flight capability compared to more primitive birds...
. Most phylogenetic studies have recovered Enantiornithes as a monophyletic group distinct from the modern birds and their closest relatives. The 2002 phylogenetic analysis by Clarke and Norell, though, reduced the number of enantiornithine autapomorphies to just four.
Enantiornithine systematics are highly provisional. The version used here, although based on many sources, is only tentative, and in need of revision in light of abundant new fossil discoveries. What appears fairly certain by now is that there were subdivisions within Enantiornithes possibly including some minor basal lineages in addition to the more apomorphic Euenantiornithes. The details of the interrelationship of all these lineages, indeed the validity of most, is disputed, although the Avisauridae, for one example, seem likely to constitute a valid group. Phylogenetic taxonomists have hitherto been very reluctant to suggest delimitations of enantiornithine clades.
Taxonomy
Subclass Enantiornithes- Basal Enantiornithes and Enantiornithes incerta sedis
- "Cathayornis" chabuensis (Early Cretaceous of Chabu, China) – cathayornithid?
- DapingfangornisDapingfangornisDapingfangornis was an enantiornithine bird. It lived during the Early Cretaceous and is known from fossils—including a complete skeleton—found in the Jiufotang Formation in Liaoning province, People's Republic of China. Small to medium-sized, it had a sternum with both long and short lateral...
(Early Cretaceous) - Enantiornithes gen. et sp. indet. CAGS-IG-02-0901 (Xiagou Early Cretaceous of Mazongshan, China)
- Enantiornithes gen. et sp. indet. CAGS-IG-04-CM-023 (Xiagou Early Cretaceous of Changma, China)
- HuoshanornisHuoshanornisHuoshanornis is an extinct genus of enantiornithine which existed in what is now Jiufotang Formation of Western Liaoning Province, China during the early Cretaceous period. Its fossil remains were found at Chaoyang City. It was first named by Xia Wang, Zihui Zhang, Chunling Gao, Lianhai Hou,...
(Early Cretaceous) – Euenantiornithes? - "LiaoxiornisLiaoxiornisLiaoxiornis is a dubious genus of enantiornithine bird. The only named species is Liaoxiornis delicatus, described by Hou and Chen in 1999. Because the species was named for a hatchling specimen, it cannot be matched with adult specimens, and so it is impossible to determine which, if any, birds...
" (Early Cretaceous) – a nomen dubiumNomen dubiumIn zoological nomenclature, a nomen dubium is a scientific name that is of unknown or doubtful application... - PengornisPengornisPengornis is the largest known enantiornithine bird from the Early Cretaceous of northeast China.the name Pengornis derives from "Peng", which refers to a mythological bird from Chinese folklore, and "-ornis", which means bird in Greek....
(Early Cretaceous) - QilianiaQilianiaQiliania is an extinct genus of early bird from the lower Cretaceous . It is a enantiornithine which lived in what is now Gansu Province, north-western China. It is known from two incomplete, semi-articulated and three-dimensionally preserved skeletons, which was found in the Xiagou Formation of...
(Xiagou Early Cretaceous) - ElsornisElsornisElsornis is a genus of enantiornithine bird. Only one species is known, Elsornis keni. It lived during the Late Cretaceous. It is known from a partially articulated fossil skeleton found in the Gobi Desert in Mongolia....
(Late Cretaceous) – close to Flexomornis? - Enantiornithes gen. et sp. indet. (Late Cretaceous of Cruzy, France)
- Enantiornithes gen. et sp. indet. MCSNM V3882a (Late Cretaceous of Ouadi al Gabour, Lebanon)
- Enantiornithes gen. et sp. indet. MZ unnumbered (Adamantina Late Cretaceous of Presidente Prudente, Brazil) – enantiornithiform?
- Enantiornithes gen. et sp. indet. Patrick Mechin collection 606 (Late Cretaceous of Bastide-Neuve, France) – alexornithid?
- FlexomornisFlexomornisFlexomornis is a genus of enantiornithine bird. Its fossils were found in Texas rocks belonging to the Woodbine Formation dating to the middle Cenomanian age of the late Cretaceous period...
(Late Cretaceous) – close to Elsornis?
- Order Iberomesornithiformes
- Superorder EuenantiornithesEuenantiornithesEuenantiornithes is a superorder of Cretaceous birds. They are considered to contain the more advanced taxa of the Enantiornithes, the dominant group of birds during the late Mesozoic...
Sometimes included in the Enantiornithes are the following taxa:
- Aberratiodontus (Early Cretaceous) – euenantiornithine (own order)?
- DalingheornisDalingheornisDalingheornis is a genus of enantiornithine bird. It lived during the Early Cretaceous about 122Ma ago and is known from a single juvenile fossil found in the upper part of the Yixian Formation in Liaoning province, People's Republic of China...
(Yixian Early Cretaceous of Dawangzhangzi, China) - ParaprotopteryxParaprotopteryxParaprotopteryx is a genus of enantiornithine bird. Though initially reported to be from the Early Cretaceous Yixian Formation, later investigation showed the fossil actually came from the Qiaotou member of the Huajiying Formation of Fengning, Hebei Province, China, and is therefore of uncertain age...
(Yixian Early Cretaceous of Fengning, China) - WyleyiaWyleyiaWyleyia is a prehistoric bird genus with a single species, Wyleyia valdensis, known from the Early Cretaceous of England. Even this is only known from a single damaged right humerus. It has been named to honor J. F. Wyley, who found the specimen in the Weald Clay deposits of Henfield in Sussex...
(Early Cretaceous) – basal? - NanantiusNanantiusNanantius eosis the name of an Early Cretaceous species of bird. It is the only described member of the genus Nanantius at present; the supposed second species Nanantius valifanovi has turned out to be a synonym of Gobipteryx minuta. N...
(Early -? Late Cretaceous) – enantiornithiform? - AbavornisAbavornisAbavornis is the name given to a genus of primitive birds from the Late Cretaceous, containing the single species A. bonaparti...
(Late Cretaceous) – euenantiornithine? - CatenoleimusCatenoleimusCatenoleimus is a prehistoric bird genus from the Late Cretaceous. It lived during the mid-late Turonian stage, around 90 million years ago...
(Late Cretaceous) - ExplorornisExplorornisExplorornis is a genus of Mesozoic birds. It lived during the mid-late Turonian stage, around 90 million years ago.Unlinke many contemporary genera, which are only known from a handful of remains that cannot be compared among each other, Explorornis is known from a handful of coracoids which are...
(Late Cretaceous) – euenantiornithine? - Horezmavis (Late Cretaceous of Kyzyl Kum, Uzbekistan) – gobipterygiform?
- GargantuavisGargantuavisGargantuavis was a genus of prehistoric bird, possibly related to Patagopteryx, containing thus far a single species, Gargantuavis philoinos. It lived during the Late Cretaceous in what is now southern France, in the Marnes de la Maurine Formation dated to around 70 mya...
(Late Cretaceous) - IncolornisIncolornisIncolornis is an extinct genus of basal birds from the Late Cretaceous . Remains have been found in the Bissekty Formation in Uzbekistan.It is only known from fragmentary coracoids...
(Late Cretaceous) – euenantiornithine? - PatagopteryxPatagopteryxPatagopteryx is an extinct monotypic genus of birds that lived during the Late Cretaceous, around 80 mya, in what is now the Sierra Barrosa in northwestern Patagonia, Argentina. About the size of a chicken, it is the earliest known unequivocal example of secondary flightlessness: its skeleton...
(Late Cretaceous) - Family Zhyraornithidae – enantiornithiform?
- ZhyraornisZhyraornisZhyraornis is a genus of prehistoric bird from the late Cretaceous period . Its fossils have been found in Bissekty Formation deposits near Dzharakuduk in the Kyzyl Kum, Uzbekistan. Two species have been assigned to this genus: Zhyraornis kashkarovi and Zhyraornis logunovi...
(Late Cretaceous)
- Zhyraornis
The three taxa "Jibeinia
Jibeinia
Jibeinia is a Genus of enantiornithine bird. Only one species is known, Jibeinia luanhera. It is known from one holotype fossil found in the Liaoning province, People's Republic of China. This fossil is now lost...
", "Vescornis
Vescornis
Vescornis is a genus of enantiornithine bird. One species is named, V. hebeiensis. The holotype fossil is in the collection of the Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences. Its catalog number is CAGS 130722. The fossil was found in Early Cretaceous rocks first...
", and "Hebeiornis
Hebeiornis
Hebeiornis was a Genus of enantiornithine bird. One species has been described, H.fengningensis.The fossil was found in the Yixian Formation, which means that Hebeiornis lived in the Barremian to early Aptian, some 125-121 mya...
", may be synonyms. (See the three articles for details on the confusion). If so, "Jibeinia
Jibeinia
Jibeinia is a Genus of enantiornithine bird. Only one species is known, Jibeinia luanhera. It is known from one holotype fossil found in the Liaoning province, People's Republic of China. This fossil is now lost...
" was published in 1997, "Vescornis
Vescornis
Vescornis is a genus of enantiornithine bird. One species is named, V. hebeiensis. The holotype fossil is in the collection of the Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences. Its catalog number is CAGS 130722. The fossil was found in Early Cretaceous rocks first...
"was described in 2004, and "Hebeiornis
Hebeiornis
Hebeiornis was a Genus of enantiornithine bird. One species has been described, H.fengningensis.The fossil was found in the Yixian Formation, which means that Hebeiornis lived in the Barremian to early Aptian, some 125-121 mya...
"was published in 1999 but it may not have been an adequate description. Therefore, if the three names truly do describe the same Genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
, the senior synonym of the three would be "Jibeinia
Jibeinia
Jibeinia is a Genus of enantiornithine bird. Only one species is known, Jibeinia luanhera. It is known from one holotype fossil found in the Liaoning province, People's Republic of China. This fossil is now lost...
". Unfortunately, Dr. Hou reported the holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
of Jibeinia
Jibeinia
Jibeinia is a Genus of enantiornithine bird. Only one species is known, Jibeinia luanhera. It is known from one holotype fossil found in the Liaoning province, People's Republic of China. This fossil is now lost...
lost in 2001.
The Late Cretaceous taxon "Cerebavis" is based on an endocranial cast and while this is not diagnostic, it is different from modern birds and as far as can be told from Ornithurae in general.