Shenzhouraptor
Encyclopedia
Jeholornis is a genus
of Mesozoic bird
s that lived approximately 120 million years ago during the Early Cretaceous
of China
. Fossil Jeholornis were first discovered in the Jiufotang Formation
in Hebei
Province, China (in what was previously Rehe Province, also known as Jehol—hence the name) and additional specimens have possibly been found in the older Yixian Formation
.
Jeholornis had long tail
s and few small teeth, and were approximately the size of turkey
s, making them among the largest birds known until the Late Cretaceous. Their diet included seeds of cycad
s, Ginkgo
or similar plants
.
and to early oviraptorosaurs like Incisivosaurus
. The lower jaws were short, stout, and curved downward, possibly an adaptation for eating seeds. Jeholornis prima lacked teeth in their upper jaws, and had only three small teeth in their lower jaws, while "J. palmapenis" had a few teeth in the middle of the upper jaw (maxilla) but none in the front (premaxilla). The upper teeth of "J. palmapenis" seem to have been angled slightly forward as in some other basal avialans. The teeth in both species were small, blunt and peg-like with no serrations.
Their arms were robust and longer than the legs, with relatively well-developed shoulder girdles indicating strong wing musculature. Their fingers were short compared to those of Archaeopteryx and also more robust. The lower legs were not particularly long, indicating that these animals were not specialized runners. The first toe, or hallux, which is reversed in modern birds and used to perch in trees, was only partially reversed in both Jeholornis species, pointing inward and slightly backward. The halluces of Jeholornis were short, but their claw was more strongly curved than those of the other toes. Unlike deinonychosaurs and some other Mesozoic birds, the claw of the second toe was not enlarged relative to the other claws. Their tail anatomy was more like those of dromaeosaurids than Archaeopteryx
, with more strongly interlocking vertebrae, and though they had a similar number of tail vertebrae (between 20 and 24) those of Jeholornis were much longer overall than those of Archaeopteryx. The only well-preserved tail feathers come from the type specimen of "J. palmapenis". This specimen shows that the
A study by Erickson in 2009 has shown that Jeholornis (along with Archaeopteryx
) had relatively slow ontogenic development, i.e. they grew very slowly, compared to most modern birds, which grow very quickly. The living kiwi birds however, have slow development, and it has been speculated that Jeholornis could have had a metabolism
similar to these.
The tails of several specimens preserve a fan of feathers (rectrices) at the tip, shorter than those on the forelimbs. The feather fan is similar to those of Microraptor
and Caudipteryx
, being restricted to the tip of the tail, unlike those of Archaeopteryx and Similicaudipteryx
which have rectrices extending down the much of the tail length. In at least one species, "Jeholornis palmapenis", there were 11 tail feathers. The feathers were short and pointed, and arced away from the body of the tail, so that the entire array of tail feathers resembled a palm frond. The tail feathers did not overlap, and so could not have formed a lift-generating surface, so the tail was probably used mainly for display.
: the type species
, Jeholornis prima (named in reference to the Jehol group of fossil beds where it was found, and the primitive appearance of the tail) and one referred species, not yet formally named but unofficially labelled "Jeholornis palmapenis" by Jingmai O'Connor and colleagues in an advance publication released on the Internet in November of 2011. The name "J. palmapenis" translates to "palm tail" in reference to the unusual arrangement of its tail feathers.
Zhou and Zhang classified Jeholornis in a new family, Jeholornithidae, of which it is the type genus, and the order Jeholornithiformes. No phylogenetic definitions for these groups were provided.
A total of five specimens have been formally described. The type specimen is in the collection of the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing. It is catalogued as IVPP V13274, and was reported in the journal Nature in 2002. Two more specimens were later accessioned by the IVPP as V 13550 and V 13553 and they were reported in the journal Naturwissenschaften in 2003. Another specimen is in the collection of the Liaoning Provincial Museum of Paleontology, and is catalogued as LPM 0193 it was reported as Shenzhouraptor in the journal The Geological Bulletin of China in 2002. An additional specimen, reported as Jixiangornis in the Journal of Nanjing University (Natural Sciences) (also in 2002) may also be a synonym of Jeholornis.
vertebrae, though Zhou and Zhang showed in 2003 that the specimen was missing several of the proximal caudals.
Several scientists have come to the conclusion that Jeholornis and Shenzhouraptor are specimens of the same species, and that one name takes precedence over the other. However, given that both names were published in print within days of each other (one in a monthly journal and one in a weekly), no consensus has been reached over which name should gain priority. The date on the article describing Jeholornis was July 25, 2002. The paper describing Shenzhouraptor was available in print on or before July 23, 2002. In 2003, Ji and colleagues made Jeholornis a junior synonym of Shenzhouraptor. In 2006, Zhou and Zhang argued that Jeholornis should have priority because it was published in a weekly journal, and that the ICZN gives priority to these over monthly journals.
In a 2006 study, Zhou and Zhang also classified Jixiangornis
as junior synonym of Jeholornis.
, each about 8-10 millimeters wide. The seeds belong to the form genus
Carpolithes, thus it is uncertain what exact lineage of plant they represent. This J. prima specimen, while about two times heavier than the type specimen Shenzhouraptor, had three small teeth in the lower jaw, whereas no teeth were visible in the latter. Two other specimens, IVPP V13353 and the aforementioned V13350 are smaller still and most certainly immature birds; they both have teeth. In the Shenzhouraptor type, the dentary and anterior skull are poorly preserved and this makes it impossible to say whether there were any teeth. The jaw is deep, the dentaries are well fused, and the teeth are reduced, and all indicate a specialized seed — feeding habit for Jeholornis.
in form and function, with forelimbs longer than hindlimbs, and a short, robust hand. However, like other primitive (non-ornithothoracean) birds and theropod dinosaurs, the shoulder blades of Jeholornis were oriented along the sides of the body, rather than on top of its back. This meant that the shoulder girdle was slung low, and according to a 2006 study by Phil Senter, would have allowed only for a typical dinosaurian motion of the shoulder. Primitive birds like Archaeopteryx, Confuciusornis, and Jeholornis would not have been able to lift their arms vertically to achieve true flapping flight, though semi-powered gliding or parachuting would have been possible.
Examination of the claw curvature in Jeholornis suggests it may have been able to perch and may have been at least partly arboreal, spending much of its time in trees. One key adaptation of modern perching birds is the reversed, opposable first toe, or "hallux." Jeholornis was initially described as having a reversed hallux, though others cast doubt on this interpretation, noting that the reversed appearance could be an artifact of the way the fossils were crushed. Indeed, in most birds with a reversed hallux, the foot bone where the reversed toe attaches is twisted, allowing the toe to point backward, but this feature is not found in any Jeholornis specimen. In a 2008 presentation for the conference of the Society of Avian Paleontology and Evolution (SAPE), Zhiheng Li and Yuguang Zhang re-examined the evidence for a reversed hallux in Jeholornis. They found that the hallux could appear reversed or not depending on the position the specimen was fossilized in, and that the toe bones showed intermediate adaptations between a reversed and non-reversed hallux. They concluded that the first toe of Jeholornis was generally held in reversed position, but had not yet acquired the advanced adaptations for reversal seen in more advanced perching birds.
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...
of Mesozoic bird
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 that lived approximately 120 million years ago during the Early Cretaceous
Early Cretaceous
The Early Cretaceous or the Lower Cretaceous , is the earlier or lower of the two major divisions of the Cretaceous...
of 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...
. Fossil Jeholornis were first discovered in the Jiufotang Formation
Jiufotang Formation
The Jiufotang Formation is an Early Cretaceous geological formation in Chaoyang, Liaoning which has yielded fossils of feathered dinosaurs, primitive birds, pterosaurs, and other organisms. . It is a member of the Jehol group. The exact age of the Jiufotang has been debated for years, with...
in Hebei
Hebei
' is a province of the People's Republic of China in the North China region. Its one-character abbreviation is "" , named after Ji Province, a Han Dynasty province that included what is now southern Hebei...
Province, China (in what was previously Rehe Province, also known as Jehol—hence the name) and additional specimens have possibly been found in the older 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...
.
Jeholornis had long tail
Tail
The tail is the section at the rear end of an animal's body; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammals, reptiles, and birds...
s and few small teeth, and were approximately the size of turkey
Turkey
Turkey , known officially as the Republic of Turkey , is a Eurasian country located in Western Asia and in East Thrace in Southeastern Europe...
s, making them among the largest birds known until the Late Cretaceous. Their diet included seeds of cycad
Cycad
Cycads are seed plants typically characterized by a stout and woody trunk with a crown of large, hard and stiff, evergreen leaves. They usually have pinnate leaves. The individual plants are either all male or all female . Cycads vary in size from having a trunk that is only a few centimeters...
s, Ginkgo
Ginkgo
Ginkgo , also spelled gingko and known as the Maidenhair Tree, is a unique species of tree with no close living relatives...
or similar plants
Spermatophyte
The spermatophytes comprise those plants that produce seeds. They are a subset of the embryophytes or land plants...
.
Description
Jeholornis were relatively large, primitive birds, with a maximum adult length of up to 80 cm (2.6 ft). Their skulls were short and high, similar to other primitive avialans like EpidexipteryxEpidexipteryx
Epidexipteryx is a genus of small avialan dinosaur, known from one fossil specimen in the collection of the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing. Epidexipteryx represents the earliest known example of ornamental feathers in the fossil record. The type specimen is...
and to early oviraptorosaurs like Incisivosaurus
Incisivosaurus
Incisivosaurus is a genus of small, probably herbivorous theropod dinosaur from the early Cretaceous Period of what is now the People's Republic of China...
. The lower jaws were short, stout, and curved downward, possibly an adaptation for eating seeds. Jeholornis prima lacked teeth in their upper jaws, and had only three small teeth in their lower jaws, while "J. palmapenis" had a few teeth in the middle of the upper jaw (maxilla) but none in the front (premaxilla). The upper teeth of "J. palmapenis" seem to have been angled slightly forward as in some other basal avialans. The teeth in both species were small, blunt and peg-like with no serrations.
Their arms were robust and longer than the legs, with relatively well-developed shoulder girdles indicating strong wing musculature. Their fingers were short compared to those of Archaeopteryx and also more robust. The lower legs were not particularly long, indicating that these animals were not specialized runners. The first toe, or hallux, which is reversed in modern birds and used to perch in trees, was only partially reversed in both Jeholornis species, pointing inward and slightly backward. The halluces of Jeholornis were short, but their claw was more strongly curved than those of the other toes. Unlike deinonychosaurs and some other Mesozoic birds, the claw of the second toe was not enlarged relative to the other claws. Their tail anatomy was more like those of dromaeosaurids 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"...
, with more strongly interlocking vertebrae, and though they had a similar number of tail vertebrae (between 20 and 24) those of Jeholornis were much longer overall than those of Archaeopteryx. The only well-preserved tail feathers come from the type specimen of "J. palmapenis". This specimen shows that the
A study by Erickson in 2009 has shown that Jeholornis (along 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"...
) had relatively slow ontogenic development, i.e. they grew very slowly, compared to most modern birds, which grow very quickly. The living kiwi birds however, have slow development, and it has been speculated that Jeholornis could have had a metabolism
Metabolism
Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...
similar to these.
Feathers
Feather traces from the wing have only been identified in two specimens, LPM 0193 (J. prima) and (SDM 20090109.1 ("J. palmapenis"). The first specimen shows that the flight feathers were asymmetrical (and therefore aerodynamic, as in modern flying birds) and up to 21 centimeters long, longer than the forearm and hand combined. The exact number of flight feathers cannot be determined from known specimens, however, as the preservation is too poor.The tails of several specimens preserve a fan of feathers (rectrices) at the tip, shorter than those on the forelimbs. The feather fan is similar to those of Microraptor
Microraptor
Microraptor is a genus of small, four-winged dromaeosaurid dinosaurs. Numerous well-preserved fossil specimens have been recovered from Liaoning, China...
and Caudipteryx
Caudipteryx
Caudipteryx is a genus of peacock-sized theropod dinosaurs that lived in the Aptian age of the early Cretaceous Period . They were feathered and remarkably birdlike in their overall appearance....
, being restricted to the tip of the tail, unlike those of Archaeopteryx and Similicaudipteryx
Similicaudipteryx
Similicaudipteryx, meaning "similar to Caudipteryx" , is a genus of theropod dinosaur of the family Caudipteridae. Its fossil remains were recovered from the Jiufotang and Yixian Formations of northeastern China, dating to the early Cretaceous Period between 124 and 120 million years ago...
which have rectrices extending down the much of the tail length. In at least one species, "Jeholornis palmapenis", there were 11 tail feathers. The feathers were short and pointed, and arced away from the body of the tail, so that the entire array of tail feathers resembled a palm frond. The tail feathers did not overlap, and so could not have formed a lift-generating surface, so the tail was probably used mainly for display.
Classification and specimens
Jeholornis contains at least two speciesSpecies
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
: the type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
, Jeholornis prima (named in reference to the Jehol group of fossil beds where it was found, and the primitive appearance of the tail) and one referred species, not yet formally named but unofficially labelled "Jeholornis palmapenis" by Jingmai O'Connor and colleagues in an advance publication released on the Internet in November of 2011. The name "J. palmapenis" translates to "palm tail" in reference to the unusual arrangement of its tail feathers.
Zhou and Zhang classified Jeholornis in a new family, Jeholornithidae, of which it is the type genus, and the order Jeholornithiformes. No phylogenetic definitions for these groups were provided.
A total of five specimens have been formally described. The type specimen is in the collection of the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing. It is catalogued as IVPP V13274, and was reported in the journal Nature in 2002. Two more specimens were later accessioned by the IVPP as V 13550 and V 13553 and they were reported in the journal Naturwissenschaften in 2003. Another specimen is in the collection of the Liaoning Provincial Museum of Paleontology, and is catalogued as LPM 0193 it was reported as Shenzhouraptor in the journal The Geological Bulletin of China in 2002. An additional specimen, reported as Jixiangornis in the Journal of Nanjing University (Natural Sciences) (also in 2002) may also be a synonym of Jeholornis.
Naming dispute
Shenzhouraptor sinensis (the name of which is derived from "Shenzhou", an ancient name for China, "raptor", Latin for "violent plunder") was described in the July 2002 issue of Geological Bulletin of China by Ji et al., the same month as Jeholornis was described by Zhou and Zhang. Two of the diagnostic characteristics which could have distinguished Shenzhouraptor from Jeholornis were its smaller size and the absence of teeth, which may be attributed to age and preservational bias. The other major difference was a different number of caudalTail
The tail is the section at the rear end of an animal's body; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammals, reptiles, and birds...
vertebrae, though Zhou and Zhang showed in 2003 that the specimen was missing several of the proximal caudals.
Several scientists have come to the conclusion that Jeholornis and Shenzhouraptor are specimens of the same species, and that one name takes precedence over the other. However, given that both names were published in print within days of each other (one in a monthly journal and one in a weekly), no consensus has been reached over which name should gain priority. The date on the article describing Jeholornis was July 25, 2002. The paper describing Shenzhouraptor was available in print on or before July 23, 2002. In 2003, Ji and colleagues made Jeholornis a junior synonym of Shenzhouraptor. In 2006, Zhou and Zhang argued that Jeholornis should have priority because it was published in a weekly journal, and that the ICZN gives priority to these over monthly journals.
In a 2006 study, Zhou and Zhang also classified Jixiangornis
Jixiangornis
Jixiangornis is the name given to a genus of basal bird from the Early Cretaceous. Like later birds, it had developed a beak, but it had a long tail, unlike modern birds. Since teeth were still present in some more advanced short-tailed birds, Jixiangornis seems to have evolved its beak...
as junior synonym of Jeholornis.
Diet
The type fossil of Jeholornis prima preserved over 50 round seeds in the area of the cropCrop (anatomy)
A crop is a thin-walled expanded portion of the alimentary tract used for the storage of food prior to digestion that is found in many animals, including gastropods, earthworms, leeches, insects, birds, and even some dinosaurs.- Bees :Cropping is used by bees to temporarily store nectar of flowers...
, each about 8-10 millimeters wide. The seeds belong to the form genus
Form taxon
Form classification is the classification of organisms based on their morphology, which does not necessarily reflect their biological relationships...
Carpolithes, thus it is uncertain what exact lineage of plant they represent. This J. prima specimen, while about two times heavier than the type specimen Shenzhouraptor, had three small teeth in the lower jaw, whereas no teeth were visible in the latter. Two other specimens, IVPP V13353 and the aforementioned V13350 are smaller still and most certainly immature birds; they both have teeth. In the Shenzhouraptor type, the dentary and anterior skull are poorly preserved and this makes it impossible to say whether there were any teeth. The jaw is deep, the dentaries are well fused, and the teeth are reduced, and all indicate a specialized seed — feeding habit for Jeholornis.
Flight and perching ability
The shoulder girdles of Jeholornis were well developed and probably allowed for better flight capability than seen in Archaeopteryx. The flight apparatus of the Jeholornis was overall quite similar to that of ConfuciusornisConfuciusornis
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...
in form and function, with forelimbs longer than hindlimbs, and a short, robust hand. However, like other primitive (non-ornithothoracean) birds and theropod dinosaurs, the shoulder blades of Jeholornis were oriented along the sides of the body, rather than on top of its back. This meant that the shoulder girdle was slung low, and according to a 2006 study by Phil Senter, would have allowed only for a typical dinosaurian motion of the shoulder. Primitive birds like Archaeopteryx, Confuciusornis, and Jeholornis would not have been able to lift their arms vertically to achieve true flapping flight, though semi-powered gliding or parachuting would have been possible.
Examination of the claw curvature in Jeholornis suggests it may have been able to perch and may have been at least partly arboreal, spending much of its time in trees. One key adaptation of modern perching birds is the reversed, opposable first toe, or "hallux." Jeholornis was initially described as having a reversed hallux, though others cast doubt on this interpretation, noting that the reversed appearance could be an artifact of the way the fossils were crushed. Indeed, in most birds with a reversed hallux, the foot bone where the reversed toe attaches is twisted, allowing the toe to point backward, but this feature is not found in any Jeholornis specimen. In a 2008 presentation for the conference of the Society of Avian Paleontology and Evolution (SAPE), Zhiheng Li and Yuguang Zhang re-examined the evidence for a reversed hallux in Jeholornis. They found that the hallux could appear reversed or not depending on the position the specimen was fossilized in, and that the toe bones showed intermediate adaptations between a reversed and non-reversed hallux. They concluded that the first toe of Jeholornis was generally held in reversed position, but had not yet acquired the advanced adaptations for reversal seen in more advanced perching birds.