Jim

■■»129 Holotype of}eholacerta furmosa, a Jehol lizard with well-preserved skin impressions, from a locality (Yixian Formation) in Pingquan, Hebei. (Courtesy: Shu-anJi/ PKU)

Jianianhualong Tengi

■n 128 Holotype of Dalinghosaurus longidigitus, a long-tailed lizard, from Sihetun locality (lower pari of Yixian Formation! in Beipiao. Liaoning. (Courtesy: Shu-anJi/ PKU)

Yixian Lizard

The Squamata (lizards and snakes) is the most successful group of modern reptiles. Squamates usually are slender animals with scutella covering their bodies. This group can be identified by skull characteristics: a high degree of skull mobility and an incomplete lower temporal bar. The Order Squamata is divided into six infraorders: Iguania, Gekkota, Amphisbaenia, Scincomorpha, Anguimorph and Serpentes. Serpentes are snakes, and the other five groups are generally called lizards.

The undoubted oldest-known lizards were found in the Middle Jurassic. They are represented by several genera of about three infraorders. Thus, lizards must have originated earlier than this time, and the earliest lizard should have appeared on earth at least from the Triassic, in view of the date of the origin ol the sphenodoncians. Santaisaurus, found near the Permian-Triassic boundary in Xinjiang, northwestern China, was referred to lizards by some paleontologists. Squamates increased rapidly from the Middle Jurassic, then they had another evolutionary radiation in the Harly Cretaceous alone

■n 128 Holotype of Dalinghosaurus longidigitus, a long-tailed lizard, from Sihetun locality (lower pari of Yixian Formation! in Beipiao. Liaoning. (Courtesy: Shu-anJi/ PKU)

with the emergence of the first snake.

Yabeinosaurus tenuis is one of the earliest found tetrapods in the Jehol Biota and the earliest studied fossil lizard in China. This species was named in 19-12 based on the material from Zaocishan, Yixian County of Liaoning Province by R. Endo and T. Shikama, who erected a new family for this genus, but it was later classified into the family Ardeosauridae by R. Hofts tetter in 1961 Another specimen from Lingyuan, Liaoning Province was referred to this species by C.-c, Young in 1958 (Fig. 1 26). The specimen of Lingyuan was regarded as from the Late Jurassic originally, but it more probably is from Jiulongshan Formation of the Middle Jurassic, and perhaps represents a different species. The holotype o{Yabeinosaurus tenuis was lost in World War II. Shu-anJi and his collaborators recently proposed a new specimen from Jingangshan, Yixian County as the neorype of this species, and some newly discovered materials may also be referred to the genus (Fig. 127).

Two other lizard species were also added to the Jehol Biota by Shu-an J i and others in recent years: Dalinghosaurus longidigitus with a long tail (Fig 128), andJeholacerta jnrmout with well-preserved scales (Fig. 129). The diversity of lizards may indicate that the Squamata was one kind of animals highly adaptive to the environments of that time.

■■»129 Holotype of}eholacerta furmosa, a Jehol lizard with well-preserved skin impressions, from a locality (Yixian Formation) in Pingquan, Hebei. (Courtesy: Shu-anJi/ PKU)

Xiao-lin Wang,

Dalinghosaurus Longidigitus

Xiao-lin Wang, n j

Zhong-he Zhou cerosaurs are flying reptiles and the first successful flying vertebrate in earth history. They first appeared in the Late Triassic together with dinosaurs, approximately 230 million years (Myr) before present, and became extinct by the end of the Late Cretaceous. Pterosaurs were the dominant creatures in the Mesozoic sky until birds joined in toward the late Mesozoic.

All pterosaurs are grouped in the order Pterosauria, which comprises two suborders: Rhamphorhynchoidea and Pterodacryloidea. The former mainly occurred from the Late Triassic to the Late Jurassic (some-extended into F.arly Cretaceous), and are relatively primitive with short neck, long tail (except the short tailed Anurognarhidac), short metacarpals, and long pedal digit V; the latter ranged from the Late Jurassic to the Late Cretaceous, and represents a more advanced group, with long neck, short tail, long metacarpal and short pedal digit V.

Many pterosaurs have been discovered from the Mesozoic deposits and most of them were preserved in the marine deposits. The Solnhofen is among the most notable pterosaur localities in the world, and the Solnhofen limestone has produced the fossils of both Rhamphorhynchoidea and Pterodacryloidea. These pterosaurs lived in the Late Jurassic of approximately 145 — 1 50 Myr ago (Tithonian). The Santana Formation in the northeastern Brazil has produced only pterodactyloid pterosaurs, which lived in the Fatly Cretaceous (Aprian-Albian, about 100 ~ 1 10 Myr before present). The Larc-Cretaceous Niobrara Formation (Santonian, around 85 Myr ago) in western Kansas, USA is famous for producing thousands of large-sized pterodactyloids. Recently, several dozens of pterosaurs have been discovered from the lacustrine deposits of the Lower Cretaceous Jehol Group in western Liaoning Province.

Many pterodactyloid pterosaurs have been reported from the Lower Cretaceous terrestrial deposits in other parts of northern China comparable to the Jehol Group. Among them are Dsungaripteras wait and Noriptents complicidens from the Tugulu Group of' the Dsungar (Junggar) Basin of Xinjiang, and Huanhepterus quingyangemis from the Zhidan Group of the Ordos Basin, Gansu Province.

Lots of pterosaur skeletons have been discovered from both the Yixian and Jiufotang Formations of the Jehol Group. These fossils comprise mostly pterodactyloids and a few rhamphorhynchoids. Among the known pterodactyloids are Eosipterus yangi and Haoptems gracilis from the Jianshangou Bed of the Yixian Formation at the Hengdaozi locality and Sihetun locality of Beipiao, Liaoning respectively, and Sinopterus clongi, Cbaoyangopterus zhangi and LiaoningopteriiSgui from the Jiufotang Formation at the Dongdadao and Dapingfang localities in Chaoyang, Liaoning. Rhamphorhynchoids comprise

>130 Holoiype of Haopterus gracilis (subacltilt, wingspan aboui 1.35 m). a pterodactyl id pterosaur, from Sihetun locality (lower pan of Yixian Formation) in Beipiao, Liaoning. The wing digit appears to be in the mouth (denoted bv a red arrow), possibly reflecting the struggle of the animal shortly before being killed by the poisonous gases from volcanic eruption. (Photo: IVPP|

Dendrorhynchoides curvidentatus from the Zhangjiagou locality in Beipiao, Liaoning and Jeholopterus ningchengertsis from the Daohugou locality in Ningcheng, Inner Mongolia.

Shu-an Ji and his colleague (1997, 1998) first reported two pterosaurs from the Yixian Formation: Eosipterus yangi and Dendrorhynchoides curvidentatus. Eosipterus is represented only by fragmentary postcranial materials, and Dendrorhynchoides, an incomplete skeleton. The former is a small to medium sized pterodactyloid with a wingspan about 1.2 m long, referable to the Pterodactylidae. It has a relatively robust forelimb, with the ulna and radius approximately 1.3 times as long as wing metacarpal. The femur is slightly smaller than 2/3 of the length of the tibia. The ulna, the first wing digital phalanx and the tibia are approximately of equal length. Dendrorhynchoides is represented by a small juvenile individual, with a wingspan of about 40 cm. This pterosaur was initially referred to the Rhamphorhynchoidae, and is now generally agreed to be a member of the Anurognathidae ("frog-jawed" pterosaurs). Its characteristics include robust cervical vertebrae, short metacarpals only about 1/4 of the length of the radius, tibia shorter than humerus, metatarsals I~IV of approximately equal length, and pedal digit V comprising two long phalanges.

Since 1998, the field crews of the IVPP, CAS have excavated abundant pterosaurs specimens. We have described five specimens (including four nearly complete skeletons and one skull), each representing a new genus and species: Haopterus gracilis, Jeholopterus ningchengertsis, Sinopterus chaoyangensis, Chaoyangopterus zhangi, and Liaoningopterus gui.

Haopterus (Fig. 130) was named in 2001 after the late Prof. Yi-chun Hao in memory of her contribution to the study of the Jehol Biota. It is a nearly complete skeleton, and probably represents a subadult with a wingspan of about 1.35 m. The skull is long and low, lacking any sagittal crest, and the rostrum is relatively pointed. The upper and lower jaws are each equipped with 12 posteriorly curved and sharp teeth, mainly distributed in the anterior part of the jaws. The forelimb is extremely robust with a long wing metacarpal. The metatarsals are slender and very small. Metatarsals I—III are less than 1/5 of the length of the wing metacarpal. The sternum is large and fan-shaped with well-developed keel, and its length and width are about the same.

Haopterus has a large skull and a pointed rostrum. The front teeth are sharp and slender, suggesting a piscivorous feeding habit. Its extremely reduced foot suggests that it probably has strong flight capability and the body was suspended by the hind limb in resting position.

Jeholopterus (Figs. 131 ~ 133) was named in 2002, and represents a nearly completely articulated pterosaur with excellently preserved fibers in the wing membrane and "hairs" in the body. The new species can be further referred to the "strange" short-tailed rhamphorhynchoid family Anurognathidae. It is the most complete and largest known individual of the family, with a wingspan of about 90 cm. Its characteristics include: a skull wider than long, resembling that of a frog; a short neck; metacarpal short and less than 1/4 of the length of the radius; extremely long pedal digit V (about 1.5 times the length of the third pedal digit) comprising two long phalanges; and a short tail.

The wing membrane and "hair"-like structures represent one of the most distinctive features of the new pterosaur. The propatagium, cheiropatagium and the uropatagium of the wing membrane can be well recognized. The cheiropatagium clearly attaches to both sides of the legs as far as the ankle. The uropatagium is between the two legs and composed of fibers that are shorter than those of the cheiropatagium. Short fibers were also preserved associated with the pedal digits, including the fifth digit, indicating that the foot was webbed and that the medially curved robust fifth digit provided both attachment and control for the uropatagium.

The purported webbed foot in Jeholopterus may indicate that this pterosaur probably lived near the water, and could even swim. This pterosaur may eat insects or other animals such as fishes. Its extremely long wings suggest strong flying capability.

It is a controversial issue as to whethes pterosaurs are warm-blooded and "haired" vertebrates. In Jeholopterus, "hairs" are short, thick and curved; they also taper from the base to the tip; and they are associated with the whole body from the neck to the tail region (Figs. 131 ~ 133). Functionally, the "hairs" of pterosaurs could be used for thermoregulation, flight or reducing noises during flight. The "hairs" in Jeholopterus may also indicate that some pterosaurs might be warm-blooded. The "hairs" of Jeholopterus bear some resemblance to the hairlike integumental structures of the feathered dinosaur Sinosauropteryx and Beipiaosaurus, which might suggest that the "hairs" of pterosaurs and the fiber-like protofeathers in Sinosauropteryx are homologous structures.

Sinopterus (Figs. 134, 135) is a recently described pterodactyloid from

Yixian Lizard

»131 Holotype ofJeholafUena nmgchengensis I Slab A. adult or subadult with wingspan about 90 cm), a short tailed pterosaur belonging to the Anurognathidae ("Frog-jawed" pterosaurs), from Daohugou locality (lowest pan of Yixian Formation I in Ningcheng. Inner Mongolia. (Photo: IVPP)

Feathered Dinosaur Skeletons

i 132 Wing membrane and the "hairs" on Jeholopterus ningchengensis, representing the most complete wing membrane and "hairs" found to date in pterosaurs. The wing membrane is relatively long and straight libers, "hairs" are generally short, wavy and curved and present all over the body. The "hairs" of this pterosaur resembles the hairlike integuments of the dinosaur Sinosauropteryx. suggesting a possible homology of these structures. (Photo: 1VPP)

Feathered Dinosaur Fossil Feathered Dinosaur Fossil

M33 Reconstruction nfjeholopieriis ningchengensis. (Artwork by: Rong-shan Li/ IVI'I'l the Jehol Biota. It is referred to the family Tapejaridae, representing its first record outside Brazil. It also represents the earliest occurrence as well as the most complete skeleton of the family.

Sinopterus has a wingspan of about 1.2 m, with the skull length about 170 mm. It is characterized by an edentulous low and long skull, with long and pointed rostrum and a horny beak. The sagittal crest of the premaxilla and dentary are low and small. The posterior process of the premaxilla is curved upward, separate from the skull, and parallel to the sagittal crest of the parietal. The nasopreorbital fenestra is large and long (length about 2.5 times of the height), exceeding 1/3 of the total length of the skull. The tibia is about 1.4 times of the length of the femur. Metatarsal III is about 22.1% of the length of the wing metacarpal, and metatarsal V is less than the 1/5 of the length of metatarsal I.

Chaoyangopterus (Fig. 136) is a medium to large-sized pterodactyloid with a wingspan about 1.85 m long. The skull is long and low, with a pointed rostrum; it is edentulous. Its manual digits I~III are robust, and wing claws large and curved. The wing digit comprises four phalanges, progressively shorter toward the distal end. Wing metacarpal and first phalanx of the wing digit are relatively short compared to Nyctosaurus gracilis from the Upper Cretaceous of western Kansas. Ratios of tibia to femur and tibia to humerus are 1.5 and 2.2, respectively, and the ratio of forelimb (humerus + ulna + wing metacarpal) to hind limb (femur + tibia + metacarpal III) is 1.1. Chaoyangopterus not only represents the first such record in Asia but also the earliest record and most complete skeleton of the family Nyctosauridae. Some revisions of the family are made, such as having four wing digits and well-developed manual digits I—III.

Liaoningopterus (Fig. 137) is referred to the family Anhangureidae. It is the largest pterosaur ever discovered in China; its teeth also represent the largest known from any pterosaurs. Liaoningopterus is a large-sized pterodactyloid, with an estimated skull length of 610 mm and wingspan about 5 m. The skull is low and long. Premaxilla and dentary are equipped with sagittal crest. The teeth are only restricted to the proximal part of the upper and lower jaws. Toothed portion of the jaws, about half the length of the skull, does not extend posteriorly to 1/3 of the nasopreorbital. Teeth near the rostral end of the jaws are huge. The fourth tooth of the premaxilla is the largest; the first and third are much smaller than the second and the fourth ones.

Members of the Pterodactylidae were previously known only in European and African Late Jurassic deposits. The discovery of the Haopterus represents the first record of the family in Asia; it also extends the distribution of the family to the Early Cretaceous. Members of the Anurognathidae were rarely known in the past; they are mainly known from the Solnhofen in Germany and Karatau in Kazakhstan. The discovery of members of this family in Liaoning represents the first record of the family in the Early Cretaceous. Sinopterus represents the first fossil record of the family Tapejaridae outside Brazil.

Two pterosaur assemblages appear to have existed in the Jehol Group, represented by the Yixian Formation and Jiufotang Formation. Among the several dozens of pterosaur specimens known from these assemblages, most are pterodactyloids, and only a few of them are rhamphorhynchoids. The assemblage from the Yixian Formation, the lower assemblage, comprises Eosipterus and Haopterus belonging to Pterodactyloidea, and Dendrorhynchoides andJeholopterus belonging to the rhamphorhynchoid Anurognathidae. This assemblage shows some resemblance to that of the Late Jurassic in Solnhofen (Tithonian) by the sharing of members of the Pterodactylidae and Anurognathidae. The assemblage is associated with the Confuciusornis avian fauna. Associated dinosaurs are also abundant, including feathered theropods Sinosauropteryx, Beipiaosaurus, Sinornithosaurus, Protarcbaeopteryx and Caudipteryx, the iguanodontid Jinzhousaurus, and the ankylosaurid Liaoningosaurus, etc. They are mainly from the Jianshangou Bed, Dawangzhangzi Bed and Jingangshan Bed of the Yixian Formation, with isotope dates ranging between 121 — 125 Ma.

The Daohugou bed of the lowest Yixian Formation (note: it is still debatable as to whether this bed should be referred to the Yixian Formation) produced Jeholopterus. Although currently there is no precise age for the fossil bed, we estimate that it cannot be older than 139 Ma, a recent 40Ar/39Ar age of the upper part of the Tuchengzi Formation, which is underlying the Daohugou bed. Our conclusion on the stratigraphic relationship between the Daohugou bed and the Tuchengzi Formation is based on the field observation of their contact at the Daohugou locality.

The upper pterosaur assemblage comprises pterosaurs from the Jiufotang Formation. All pterosaurs collected so far from this formation are pterodactyloids. Among them Sinopterus, Chaoyangopterus and Liaoningopterus have been described. No rhamphorhynchoid has been discovered among over

134 Holotype of Sinop/frus dongi (subadult, wingspan about 1.2 m), a tapejarid pterosaur, from Lamagou locality (Jiufotang Formation), Chaoyang. liaoning. (Photo: IVPP)

135 Close-up view of the skull of Sinopterus dongi (about 17 cm long). (Photo: IVPP)

Feathered Dinosaur FossilFeathered Dinosaur Fossil

a dozen specimens known from the Jiufotang Formation. The upper assemblage shows more resemblance to that of the Early Cretaceous Santana Formation (Aptian/Albian) in comprising only pterodactyloids such as the Tapejaridae and the Anhangueridae. The age of the Jiufotang Formation is slightly older than the Santana Formation. This pterosaur assemblage is associated with the Cathayorttu avian fauna that includes birds such as Si/ton/is,

Yamnvh, Sapeornis and Jtbolornii. Associated dinosaurs include the feathered dromaeosaurids A\jcrortiptor zhaoianus and M.gui. Although no radiometric date has been obtained directly from the beds in which the pterosaurs were collected, the basalt overlying the Jiufotang Formation was dated as 110 Ma in Inner Mongolia, and therefore, the temporal distribution of this formation is estimated as I 10—120 Ma.

Jiufotang Formation
m 136 Holotype of Chaoyongnpterus zlwngi (wingspan about 1.85 m), a nyctosaurid pterosaur, from Gonggao locality (jiufotang Formation), in Chaoyang, Liaoning. (Photo: 1VPP)
Feathered Dinosaur Fossil

1137 Holotype of Liaoningopterusgui (estimated wingspan about 5 m. skull length (SI cm), a large pterodactyloid with the largest tooth known from any pterosaurs, from Xiaoyugou locality (Jiufotang Formation) in Chaoyang, Liaoning. (Photo: IVPP)

Coelurosauria Feathers

139 Close-up view of the integuments of SUnsauropleryx prima. The filamentous integuments represent primitive feathers and this discovery gives us a glimpse at the origin and early evolution of feathers. (Photo: Da-jian Li/CAS)

138 Holotype of Sinasauropteryx prima, a rooster-sized theropod dinosaur, from Sihetun locality (lower part ol Yixian Formation). Beipiao, Uaoning. (Photo: Da-jian Li/CAS)

Xing Xu

Sinosauropteryx

wm 140 Reconstruction of Sinosauropteryx prima. Although a few artists restored some non-avian dinosaurs with feathers or featherlike integuments as early as 1970s, the discovery of Sinosauropteryx prima provides the firsi fossil evidence for such a restoration. {Art: Xiao-Nan Zeng/ KIB)

Dinosaurs are among the best known prehistoric a I animals. They were the world's conquerors during the Mesozoic, representing one of the most successful vertebrate groups. That is why the Mesozoic Era is also called the "Age of Dinosaurs' . China is extraordinarily rich in dinosaur fossils, the record of which spans almost the entire age of dinosaurs. Recently, the dinosaur remains from the Lower Cretaceous Jehol Group have aroused worldwide attention. The feathered dinosaurs, in particular, have challenged the conventional idea on both dinosaurs' appearance and their life history.

Most major dinosaur groups are represented in the Jehol Group, including sauropods, theropods, ornithopods, ceratopsians and ankylosaurs. The following paragraphs briefly describe some important dinosaur tax a from the Jehol Biota with comments on their evolutionary implications.

Coelurosaurs are a group of derived theropod dinosaurs, including the giant tyrannosaurids. the long-clawed therizinosauroids, the deep-skulled oviraptorosaurs, and the volant birds anil their close relatives — the agile dromaeosaurs and the large-brained troodontids. In the Jehol Biota the non-avian coelurosaurians are represented by 12 species in 10 genera.

Sinosanroptcryxprima (Eigs. 138— 1 40), the first named coelurosaurian from theJehol Biota, was fount! in western Liaoning in 1996. Ir is about the wm 140 Reconstruction of Sinosauropteryx prima. Although a few artists restored some non-avian dinosaurs with feathers or featherlike integuments as early as 1970s, the discovery of Sinosauropteryx prima provides the firsi fossil evidence for such a restoration. {Art: Xiao-Nan Zeng/ KIB)

Caudipteryx Fossil

14! A complete skeleton of Caudipteryx zoui. ,m emu-sized theropod dinosaur, from Zhangjiagou locality (lower part of Yixian formation), Reipiao. Maoning. red arrow denoting the gizzard stones. (Photos IVPP)

Feathered Dinosaurs

14! A complete skeleton of Caudipteryx zoui. ,m emu-sized theropod dinosaur, from Zhangjiagou locality (lower part of Yixian formation), Reipiao. Maoning. red arrow denoting the gizzard stones. (Photos IVPP)

■«142 Reconstruction of Caudipteryx zoui. Similar to its oviraptond relatives. Caudipteryx is a cursorial animal, with feathers but could not fly. (Art: Anderson Yang)

size of a rooster, with a large skull and sharp teeth, very short arms and an unusually long tail. Although it is a primitive coelurosaurian, osteologically quite different from birds compared to advanced rum-avian coelurosaurians, Stnosauropteryx occupies an im|x>rtant position in understanding the origin of birds because of the presence ol a h.iirlike covering on its body. Many paleontologists regarded the hairlike structures as primitive feathers used for insulation, bur others disagreed and believed they arc unrelated to feathers The following year, two other feathered dinosaurs were found from the same area. One was named as Profanbaeopteryx roiuita and the other Caudipteryx zoui (Figs. 1-41, l42>. These two dinosaurs are comparatively more similar to birds in terms of bony structure than is Stnosauropteryxprima; yet both were unable to fly. Pntatxhueopteryx has sharp teeth and long arms, and is similar to, hut does not belong to, the dromaeosaurids. Dromaeosaurids are one ot the most birdlike dinosaur groups thar also include the small-sized Ve/otiraptor, figured in the movie "Jurassic Park". Caudipteryx has short arms like Compsogmitbtis but other features suggest it is an oviraptorosaurian dinosaur. It has a tall and short skull atypical of that in therop<xl dinosaurs, long legs, and short tail. The gizzard stones (Fig. 1-11) indicate that Caudipteryx zoui is likely a herbivore. Both Protanhaeopteryx and Caudipteryx have unquestionable true feathers that are composed of a prominent shaft and (lat vanes. Unlike flight feathers of birds, the long feathers on the arms and tails of Protanhaeopteryx and Caudipteryx have symmetrical vanes, suggesting that

Caudipteryx

mm 143 Holotype ofBeipiaosaurus inexpectus, the largest feathered dinosaur found from thejehol Biota to date with estimated total length more than 2 m. from Sihetun locality (lower part of Yixian Formation). Beipiao, Liaoning. Different from the typical theropods, Beipiaosaurus has numerous tiny teeth, and broad feet suggestive of a slow lifestyle. (Photo; IVPP)

Feathered Dinosaur Skeletons

mm 144 Close-up view of integuments of Bapiousmirus inexpectus. These filamentous structures probably represent the primitive feathers and may have wider distribution among norv-avian therppods. (Photo: IVPP)

they .ire not suitable for flight.

This was the first time in history that feathers had been discovered on non-avian animals — living or extinct, but it was not the last time, fortunately, In 1999, two other feathered dinosaurs were again reported from western Liaoning. Btipiiiasauriii mexptctus (Figs. 1 13, 1 14) is the biggest theropod yet discovered from Liaoning. It is more than 2 meters long, with tiny teeth, a bulky body, and a short tail. Although some features of Beipiuosai/nu suggest it perhaps a plant eater, Btipiaosaurm has unusually long, Curved, sharp claws on irs hands as in meat-eating dinosaurs. Sitiwiitbosaurus miUetiii (Figs. 145—149), the second species, is a close relative of Velociraptor but much smaller, it has dagger-like teeth, long arms that could flap, and a rodlike, stiff tail. Actually Sinornithosaurus represents one of the most birdlike dinosaurs, and is more closely related to birds than the other species mentioned above. Although no vaned feathers were found on either Beipiaosaun/s or Sit/omiihosa//r/ts specimens, the featherlike structures on the two dinosaurs are apparently more complex than those of Sinosauropteryx in having a branched structure.

In 2000, the sixth and seventh feathered dinosaur species were reported from western Liaomng. One is a new species of an established genus — Caudipteryx dongi (Fi^s. 150, 151), which helps clarify some morphological features of the genus. The other one is a tiny dinosaur, less than 40 cm long. This dinosaur, named as Micraraptor zhaoianus (Figs. 1 52 — 154), represents the smallest adult dinosaur found to date. Like Sinoruitbosa/nw, it is also a dromaeosaurid, M/oorap/or is the most birdlike among all known dinosaurs, it is small and has an expanded braincase like birds, long arms that could flap, and feet that show adaptations to dwelling in trees. This finding suggests that some small-sized non-avian dinosaurs moved into the trees in order to escape larger hunters or chase small prey, and gradually evolved flight capability living in the trees. A halo of featherlike structures surrounds the fossil skeleton of SYurmaptnr zbaoianus, some of which bear the central shaft. Although the preservation does not allow us to draw a conclusion that Micromptor zbamanus had vaned feathers, it is most likely that it did.

In 2002, three new coelurosaurian theropods have been reported from western Liaoning and adjacent Inner Mongolia. Two of them, namely Simvenatur changii (Figs. 155, 156) and Inctstiosaurusgauthim (Figs. 157, 158) were from the same fossil bed, the Lujiatun Bed of the lowest Yixian Formation (refer to Chapter 1 for stratigraphic information). Although no feathers were found on these specimens, maybe due to the nature of the deposits — coarse sandstone, they most probably had feathers on their body during life. Sinovetiator is a croodonrid, one of the most birdlike dinosaur groups and very similar in some features to the dromaeosaurids. Again, Sinovenator is a small animal less than one meter long. Irs braincase is very similar to early birds, indicating a relatively high level of intelligence. Despite being a theropod dinosaur usually regarded as carnivores, Imisivosaurus is unusual in having teeth similar to those of the plant-eaters.

The third theropod reported in 2002 was a small arboreal dinosaur, Epidttidnsaur/ts ningebeugensis (Figs. 159, 160), and its holotype was collected from southeastern Inner Mongolia. It has an extremely long third manual digit, indicating a type of adaptation previously unreported from the Mesozoic. Epidettdrosaurus has some features previously unknown in non-avian dinosaurs, including a fully reversed hallux. Its precise phylogenetic position is not yet clear though Epidtudrosaurtu is tentatively regarded as the closest relative of

,145 Holotype of Sinornithosourus millenii. a small theropod dinosaur (estimated length I.I ml. from Sihetun locality (lower part of Yixian Formation), Beipiao. Liaoning. It has feathered fore-limbs that can move the way birds' wings do. indicating that non-avian theropods were pre-adapted for evolving flying capacity. (Photo: IVPPI

Vi.y

z,j, 146 Skull of Sinornithosaurus millenii, showing the sharp and serrated teeth of a seemingly ferocious animal. (Photo: fVPP|

Feathered Dinosaur Skeletons

148 Wishbone of Sinorniihusaurus milkim. a structure previously thought to be present only in birds, but recently found to be widespread among dinosaurs. It is morphologically identical to that of Archacopteryx, the most primitive bird. (Photo: IVPP)

Xl/< 147 Tlie rodlike tail bones of Sinornithosauna milk-mi, unique to the dromaeosaurids, indicating a stiff tail. (Photo: IVPP)

Feathered Dinosaur Skeletons

Xl/< 147 Tlie rodlike tail bones of Sinornithosauna milk-mi, unique to the dromaeosaurids, indicating a stiff tail. (Photo: IVPP)

149 Close-up view ofthe integuments of Sinornithosaurus millenii. showing the branched filamenrous integuments, a unique feature in feathers. (Photo: IVPP)

IaJ, i 50 Holotype of Caudipteryx dongi, similar in size to C- zoui. from Zhangjiagou locality (lower part of Yixian Formation), Beipiao, Liaoning. iPholo: IVPPl

IaJ, i 50 Holotype of Caudipteryx dongi, similar in size to C- zoui. from Zhangjiagou locality (lower part of Yixian Formation), Beipiao, Liaoning. iPholo: IVPPl

Feathered Dinosaur Fossils
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ZaJ4 151 The remiges preserved on the Caudipieryx dongi specimen. Different from the (light feathers in volant birds, the remiges on the forelimbs of Caudipieryx dongi have symmetrical vanes, indicating a lack of aerodynamic function. (Photo: IVPP)

■n 152 Holotype ot Microraptor zhaoianus. the smallest known adult non-avian dinosaur (estimated total length less than 40 cm), from l.angshan locality (Jiufotang Formation) in Chaoyang, Liaoning. (Photo: IVPP)

153 The pes of Micraraptor zhaoianus, some of its pedal features suggestive of art arboreal habit, indicating that the theropod ancestors of birds might have passed through an arboreal phase. (Photo: IVPP)

Jehol Reconstruction

2610.12

«u 154 Reconstruction ofMicro-raptor zhaoianus. (Art: Rong-shan Li/ IVPP|

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Feathered Dinosaur Fossil

1155 Partial skull of the holotype of Sinuvenalor changii. a small theropod dinosaur with estimated body length less than 1 m. from Lujiatun locality (lowest part of Yixian Formation) in Beipiao. Liaoning. (Photo: IVPP)

Feathered Dinosaur Fossil

1155 Partial skull of the holotype of Sinuvenalor changii. a small theropod dinosaur with estimated body length less than 1 m. from Lujiatun locality (lowest part of Yixian Formation) in Beipiao. Liaoning. (Photo: IVPP)

1156 Reconstruction of Sinovenator chongii. (Art: Michael W. Skrepnick/ FMNH)

Feathered Dinosaur Skeletons

1156 Reconstruction of Sinovenator chongii. (Art: Michael W. Skrepnick/ FMNH)

Feathered Dinosaur Fossils

158 Reconstruction of Incisivosaunis gauthieri. (Art: Portia Sloan).

■»157 Holotype of Incisivosaunis gauthieri (skull length about 1 I cm), a small oviraptorosaur with peculiar tooth morphology, from Lujiatun locality (lowest part ofVixian Formation) in Beipiao, Liaoning, (Photo: IVPP)

158 Reconstruction of Incisivosaunis gauthieri. (Art: Portia Sloan).

the birds.

A new feathered dinosaur, Microraplorgui (Figs. 161, 162), was described early in 2003. It is the second species of Microraptor, and a small lightweight animal of 77 cm long, with a rodlike long tail. This dinosaur probably lived in the trees. Surprisingly ir has long pennaceous feathers not only on its forelimbs and tail, but also on its hind limbs (the so-called "four-winged dinosaur"). Furthermore, the feathers were almost identical to those of living birds, with asymmetrical vanes, a feature associated with flight or gliding in extant birds. It is very likely that Microraptor gui is a gliding animal, representing an intermediate stage between the flightless dinosaurs ami the volant birds.

Amazingly, as many as 12 coelurosaurian theropod species have been reported from a small area in western Liaoning and the adjacent Inner Mongolia in last a few years. More surprisingly, these discoveries have provided us with much-needed information on important issues such as the origin of feathers and bird flight that was unavailable from all other known dinosaur specimens collected worldwide over the last century and a half.

Before these discoveries from western Liaoning, there was little fossil evidence for studying the origin of feathers. Due to their structural complexity, feathers are very distinctive from all other integumentary structures, and their abrupt appearance in the fossil record has been perplexing. Now that the hypothesis of dinosaurian origin of bird has been well established, it theoretically follows that feathers should be present on some birdlike theropods. However, no intermediate structures that could be feather precursors were preserved in the related theropods. On the contrary, most evidence suggested that dinosaurs were scaled animals, including some theropod dinosaurs. For example, some psittacosaurid specimens from the same localities as the feathered theropod specimens preserved beautiful skin impressions, showing that these animals had scaly skin. The feathered dinosaurs from Liaoning are just what many paleontologists were anticipating, and thus provide direct fossil evidence tor the hypothesis that feathers are not unique to birds and can be traced back into the dinosaurian ancestors of birds. The feather)ike structures on these different dinosaurs are diverse in morphology, but display an evolutionary trend in complexity approaching the origin of birds. Sbwsattropteryx has simple feathers; Beipiaosaurus and Sinornithosaums have branched feathers but bear no vanes; Protarchaeopteryx and Caueiipteryx have developed vaned feathers. The lack of vaned feathers on Beipiaosaurus and

Epidendrosaurus Ningchengensis

1159 Holotype of Epklendrosaurus mngchengensis. a small theropod with the size of a house sparrow, from Daohugou locality in Ningcheng. Inner Mongolia. (Photo: IVPH)

Epidendrosaurus SizeEpidendrosaurus Ningchengensis

1160 Reconstruction of Epidendrosaurus ningchengensis. showing its arboreal features. (Art: Rong-shan Li/ IVPI').

Sinornithosaurui are most likely due ro preservations. In fact, the most recent discovery suggests that Sinomitbasaurus and Ahcroraptnr have vaned feathers as I'ro/arcbaeoptviyx and Caudipteryx do.

Here is the current picture of feather evolution: most dinosaurs, including all ornithischian ("bird-hipped" dinosaurs), all prosauropods and saurop»x.ls, and some primitive theropods, are similar to typical reptiles in that their bodies are covered with scales or tubercles; the first feather evolved in the early stages of coelurosaurian dinosaurs, and was a simple, hairlike structure, probably used to keep the animal warm; more complex feathers evolved later, and display a branching structure; long, vaned feathers evolved in some maniraptoran dinosaurs, probably including therizinosauroids, oviraprorosaurs, troodonrids anil dromaeosaunds, and these complex feathers were likely for display; finally, asymmetrical flight feathers evolved anil are used to generate lift during flight. Therefore, feathers appeared before the origin of birds (Tig 163) anil early feathers functionally had nothing to do with flight. In the future, if we find a feathered fossil animal, we need to be careful when determining what kind of animal it is — it could be a bird, but it could also be a flightless dinosaur.

Compared to the highly publicized theropod dinosaurs from the Jehol Fauna, the ornithischian dinosaurs remain little known, despite the fact that the first dinosaurian discovery from the Jehol Fauna was an ornithischian. To date, three major ornithischian groups have been reported from the Jehol Biota, i.e., ankylosaurs, ornithopods, and ceratopsians.

The ceratopsians are a late group of herbivorous dinosaurs, mostly restricted to the Cretaceous period. They are characterized by some cranial modifications, including the unique rostral bone that is otherwise unknown in any other dinosaurs. In 1970s some ceratopsian dinosaur specimens were collected from the Jiufotang Formation of western Liaoning. Identified later as a new species of psittacosaurid dinosaur, Psittacosaurus meikryingensis has a relatively tall anil rounded skull (Fig. 164). Psittacosaurids, known only from the Farly Cretaceous of Asia, are a basal lineage of the ceratopsian dinosaurs. They are facultative biped, different from the more derived, quadrupedal neoceratopsians. The other ceratopsian from the Jehol Fauna is the goat-sized IJawratopj yanzigviiensis (Figs. 165, 166), a neoceratopsian, which belongs to the second major lineage of the ceratopsians. It has only rudimentary horns and a frill, different from the more derived neoceratops that usually weigh much heavier and have massive horns and a wide frill. Liaoceratops yanzigontmii is the smallest, oldest and most primitive neoceratopsian ever found.

The ornithopods represent the most diverse group of ornithischian dinosaurs, including the primitive small-bodied forms such as Heterodontosauridae, the intermediate representatives such as the famous Iguanodon, and the derived large-bodied forms such as duck-billed dinosaurs. The first ornithopod found from the Jehol Fauna isjehoiosa/trus sbanyuantmis (Fig. 167). It is a small dinosaur less than one meter long, and appears to be very primitive in a number of features despite being a Cretaceous ornithopod._/t,W«j.///»y/.i is placed in the Ornithopoda, but displays a few features similar to those of ceratopsian dinosaurs. It is a potentially important taxon for understanding the early evolution of the ornithischian dinosaurs. Jinzbomaurus yangi (Fig. 168) represents the second o

1161 Holotype of Microraptor gui (total length 77 cml. a small dromaeosaurid and the so-called "four-winged dinosaur" characterized by feathers on all its limbs, from Dapingfang locality (Jiufotang Formation) in Chaoyang, Liaoning. (Photo: IVPP)

1162 Reconstruction of Microraptor gui. (Art: Portia Sloan)

1161 Holotype of Microraptor gui (total length 77 cml. a small dromaeosaurid and the so-called "four-winged dinosaur" characterized by feathers on all its limbs, from Dapingfang locality (Jiufotang Formation) in Chaoyang, Liaoning. (Photo: IVPP)

1162 Reconstruction of Microraptor gui. (Art: Portia Sloan)

ornithopod species found from the Yixian Formation of western Liaoning. About seven to eight meters long, it represents the largest named dinosaur from the Jehol Group. J 'tttzbousaurus is similar to Iguanodon, one of the earliest named di-nosaurs in the world, in many features, such as the spike-like pollex. Interestingly, it has a combination of primitive and derived characters, some features more primitive than the contemporary iguanodontids but others similar to those of derived hadrosaurs.

Ankylosaurs are a group of highly specialized ormthischian dinosaurs and easily recognized by their extensive body armor. Liaortingosanrns paradoxus (Fig. 169) represents the only known ankylosaur from the Jehol Biota. It is a beautifully preserved juvenile specimen less than 40 cm long. Liaoningosat/rns has a large, somewhat shell-like bony plate under its belly. This discovery is the first record of such a structure among dinosaurs, thus adding to our knowledge of the morphological diversity of dinosaurs. Though a cladistic analysis has placed Liaoningosaurus in Nodosauridae, a number of distinct ankylosaurid features seem to bridge the morphological gaps between the two ankylosaurian families. It is also possible that LiaoningoututKS is neither ankylosaurid nor nodosaurid, but rather a basal ankylosaur.

So far, 17 new dinosaurian species have been reported from the Jehol Biota. The discoveries of feathered dinosaurs are significant because they provide the most compelling evidence supporting the hypothesis that birds were descended from dinosaurs, and also improve our understanding of the origin and early evolution of feathers and the origin of bird flight by indicating that feathers evolved before powered flight, and that flight probably evolved through a gliding stage. Other discoveries of non-feathered dinosaurs from western Liaoning are also very important because they have changed dinosaurian phylogenetic patterns proposed by previous studies and significantly advanced the study on character evolution for many dinosaurian lineages. The recenr dinosaurian discoveries from the Jehol Group have provided the most comprehensive evidence yet of dinosaurian soft tissues, and will undoubtedly produce many more insights in the future.

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Pterosauria

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