''Chuanqilong'' (meaning "legendary dragon") is a monospecific

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

of basal ankylosaurid

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

from the

Liaoning Province Liaoning () is a coastal province in Northeast China that is the smallest, southernmost, and most populous province in the region. With its capital at Shenyang, it is located on the northern shore of the Yellow Sea, and is the northernmost ...

China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's List of countries and dependencies by population, most populous country, with a Population of China, population exceeding 1.4 billion, slig ...

that lived during the

Early Cretaceous The Early Cretaceous (geochronology, geochronological name) or the Lower Cretaceous (chronostratigraphy, chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145& ...

(late

Barremian The Barremian is an age in the geologic timescale (or a chronostratigraphic stage) between 129.4 ± 1.5 Ma (million years ago) and 121.4 ± 1.0 Ma). It is a subdivision of the Early Cretaceous Epoch (or Lower Cretaceous Series). It is preceded ...

Aptian The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous Epoch or Series and encompasses the time from 121.4 ± 1.0 Ma to 113.0 ± 1.0 Ma (million years ag ...

stage, 122.0 to 118.9 Ma) in what is now the

Jiufotang Formation The Jiufotang Formation ( Chinese: 九佛堂组, pinyin: ''jiǔfótáng zǔ'') is an Early Cretaceous geological formation in Chaoyang, Liaoning which has yielded fossils of feathered dinosaurs, primitive birds, pterosaurs, and other organisms (see ...

. The type and only species, ''Chuanqilong chaoyangensis'', is known from a nearly complete

skeleton A skeleton is the structural frame that supports the body of an animal. There are several types of skeletons, including the exoskeleton, which is the stable outer shell of an organism, the endoskeleton, which forms the support structure inside ...

with a

skull The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, th ...

of a juvenile individual. It was described in

2014 File:2014 Events Collage.png, From top left, clockwise: Stocking up supplies and personal protective equipment (PPE) for the Western African Ebola virus epidemic; Citizens examining the ruins after the Chibok schoolgirls kidnapping; Bundles of wa ...

by Fenglu Han, Wenjie Zheng, Dongyu Hu, Xing Xu, and Paul M. Barrett. ''Chuanqilong'' shows many similarities with '' Liaoningosaurus'' and may represent a later

ontogenetic Ontogeny (also ontogenesis) is the origination and development of an organism (both physical and psychological, e.g., moral development), usually from the time of fertilization of the egg to adult. The term can also be used to refer to the s ...

stage of the taxon. ''Chuanqilong'' was a medium-sized

ankylosaur Ankylosauria is a group of herbivorous dinosaurs of the order Ornithischia. It includes the great majority of dinosaurs with armor in the form of bony osteoderms, similar to turtles. Ankylosaurs were bulky quadrupeds, with short, powerful limbs. ...

, with an estimated length of 4.5 metres (14.8 feet), although it has been suggested that it would have been larger due to the immature age of the type specimen. It had a triangular skull and a neck that was protected by bands of osteoderms known as cervical half rings. The rest of the body was covered in osteoderms and ossicles of various shapes and sizes. Unlike derived ankylosaurids, the end of its tail lacked a club. Like other ankylosaurids, it was

quadrupedal Quadrupedalism is a form of locomotion where four limbs are used to bear weight and move around. An animal or machine that usually maintains a four-legged posture and moves using all four limbs is said to be a quadruped (from Latin ''quattuor ...

with robust forelimbs and hindlimbs.

Discovery and naming

A nearly complete

was collected by local farmers from a single

quarry A quarry is a type of open-pit mine in which dimension stone, rock, construction aggregate, riprap, sand, gravel, or slate is excavated from the ground. The operation of quarries is regulated in some jurisdictions to reduce their envir ...

in the

. The skeleton was recovered from the

which dates to the late

stages of the

period, 122.0 to 118.9 Ma. The specimen was named and described in

by Fenglu Han, Wenjie Zheng, Dongyu Hu, Xing Xu, and Paul M. Barrett. The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of seve ...

specimen, CJPM V001, consists of a nearly complete

and

, with only the distal portion of the caudal series missing, and represents a juvenile individual. The authors noted that the specimen was at a more advanced ontogenetic stage than the specimens of the

sympatric In biology, two related species or populations are considered sympatric when they exist in the same geographic area and thus frequently encounter one another. An initially interbreeding population that splits into two or more distinct species s ...

'' Liaoningosaurus'' based on the larger size of the type specimen, the size of the

orbit In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such as ...

and the

tooth A tooth ( : teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, ...

count. The specimen is preserved two-dimensionally, with only the ventral side being visible. Most of the skull is compressed dorsoventrally and most of the vertebral column is disarticulated, while the limbs are preserved in articulation. The type specimen is currently housed at the Chaoyang Jizantang Paleontological Museum, while a cast of the specimen (IVPP FV 1978) is housed at the

Institute of Vertebrate Paleontology and Paleoanthropology The Institute of Vertebrate Paleontology and Paleoanthropology (IVPP; ) of China is a research institution and collections repository for fossils, including many dinosaur and pterosaur specimens (many from the Yixian Formation). As its name sugg ...

. The

generic Generic or generics may refer to: In business * Generic term, a common name used for a range or class of similar things not protected by trademark * Generic brand, a brand for a product that does not have an associated brand or trademark, other ...

name, ''Chuanqilong'', is derived from the Chinese words "''Chuanqi''" (legendary), in reference to the abundance of fossils of western Liaoning, and "''long''" (dragon). The specific name, ''chaoyangensis'', refers to the broader geographical area which encompasses the type locality. In 2014, the impressions of a scapulocoracoid and

humerus The humerus (; ) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a r ...

belonging to an indeterminate

with an estimated body length of 6.0-8.6 metres (19.7-18.2 feet) were described from the Jiufotang Formation and, at the time, was the first ankylosaur described from the formation. A Canadian Society of Vertebrate Palaeontology abstract book that was published in 2019 mentioned that the type and only known specimen of ''Chuanqilong'' actually represented an adult individual, in contrast to the interpretation of Han ''et al.'' (2014), and may have been ''Liaoningosaurus'' at a different and later ontogenetic stage.

Description

Size and distinguishing traits

Han ''et al.'' (2014) gave ''Chuanqilong'' an estimated length of 4.5 metres (14.8 feet). However, the authors suggested that it could have reached larger sizes as the type specimen represents a juvenile individual. The describing authors indicated two distinguishing traits. Both of these are

autapomorphies In phylogenetics, an autapomorphy is a distinctive feature, known as a derived trait, that is unique to a given taxon. That is, it is found only in one taxon, but not found in any others or outgroup taxa, not even those most closely related to t ...

, unique derived characters. The quadrate has a

glenoid fossa The glenoid fossa of the scapula or the glenoid cavity is a bone part of the shoulder. The word ''glenoid'' is pronounced or (both are common) and is from el, gléne, "socket", reflecting the shoulder joint's ball-and-socket form. It is a sha ...

that is at the same level as the

dentary In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...

tooth row. The distally tapering

ischium The ischium () form ...

is constricted at midshaft length. Other distinguishing traits include the presence of a long retroarticular process, the presence of a lacrimal that is slender and wedge-like, a ratio of

femur The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates ...

length of 0.88, the width of the proximal end of the humerus is half of the length of the humeral shaft, and the presence of subtriangular unguals.

Cranium

In ventral view, the

is triangular. The

maxilla The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. T ...

has a buccal with a notched margin that is shallow and flattened, while an antorbital fenestra is present in the caudodorsal region. A slender, wedge-shaped lacrimal forms the rostral margin of the

and a long supraorbital contacts the lacrimal rostroventrally. A bone which might be composed of the

squamosal The squamosal is a skull bone found in most reptiles, amphibians, and birds. In fishes, it is also called the pterotic bone. In most tetrapods, the squamosal and quadratojugal bones form the cheek series of the skull. The bone forms an ancestral co ...

and the

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 ...

has a subrectangular outline and grooves that are subparallel. The left quadrate has a rectangular head and is straight, with the shaft forming a wide and shallow depression underneath the quadrate head. Unlike nodosaurids, the quadrate isn't fused with the squamosal. The

pterygoid process The pterygoid processes of the sphenoid (from Greek ''pteryx'', ''pterygos'', "wing"), one on either side, descend perpendicularly from the regions where the body and the greater wings of the sphenoid bone unite. Each process consists of a me ...

has a transversely expanded ventral end which is composed of two mandibular condyles, and has an outline that is subrectangular. As in most other

ankylosaurs Ankylosauria is a group of herbivorous dinosaurs of the order Ornithischia. It includes the great majority of dinosaurs with armor in the form of bony osteoderms, similar to turtles. Ankylosaurs were bulky quadrupeds, with short, powerful limbs. ...

, the medial condyle is wider across and extends further towards the underside than the lateral condyle. As in most ankylosaurs, with the exception of ''

Ankylosaurus ''Ankylosaurus'' is a genus of armored dinosaur. Its fossils have been found in geological formations dating to the very end of the Cretaceous Period, about 68–66 million years ago, in western North America, making it among the last of th ...

'', the left maxilla has at least 20

alveoli Alveolus (; pl. alveoli, adj. alveolar) is a general anatomical term for a concave cavity or pit. Uses in anatomy and zoology * Pulmonary alveolus, an air sac in the lungs ** Alveolar cell or pneumocyte ** Alveolar duct ** Alveolar macrophage * M ...

. The rostral maxillary teeth that are preserved are smaller than the caudal teeth, with their crowns being as tall as they are wide and their bases being swollen with a weak cingulum. The teeth lack crescentic cingula. A rostral maxillary tooth crown has small denticles and cusps present. Some of the teeth have denticles that taper with a round cross-section at the base. The

mandible In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...

is similar to that of other basal ankylosaurids as it is long and shallow. However, it lacks an

osteoderm Osteoderms are bony deposits forming scales, plates, or other structures based in the dermis. Osteoderms are found in many groups of extant and extinct reptiles and amphibians, including lizards, crocodilians, frogs, temnospondyls (extinct amp ...

on the underside margin unlike other basal ankylosaurids. The absence of the osteoderm might be a result of incomplete preservation as it may not have been fused to the mandibular bone due to the immature age of the holotype. If an osteoderm was presents, it might have been restricted to the sides corner of the mandible. The dentary tooth row is not as strongly sinusoidal as those of derived ankylosaurs and is straight. The dentary has at least 20 alveoli present, with most of the teeth missing. The teeth preserved are similar to the maxillary teeth. The symphysis of the right dentary is downturned slightly and the cross-section is sub-triangular. As in nodosaurids, the coronoid eminence projects above the level of the dentary tooth row. Below the coronoid eminence is the large adductor fossa. The retroarticular process is long and slender, while the articular is small. The glenoid fossa is unlike that of other ankylosaurs as it is situated at the same level as the dentary tooth row.

Postcrania

The

centra Centra is a convenience shop chain that operates throughout Ireland. The chain operates as a symbol group owned by Musgrave Group, the food wholesaler, meaning the stores are all owned by individual franchisees. The chain has three different ...

of the cervical and dorsal vertebrae are spool-like. The cervical centra are shorter than they are wide, while the dorsal centra are longer than tall. and the sacral centra are wider than it is long. All of the centra of the dorsal vertebrae lack a ventral keel. The sacral ribs have a dumbbell-shaped outline and are robust. Present on the caudal vertebrae are deep longitudinal grooves. The centrum of a middle caudal vertebra has a square outline in lateral view. The upper part of the sides of the centrum possesses a transverse process that has been reduced to a small nodular process. The

neural spines The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic i ...

have a arc-shaped outline and are elongated. The facets of the prezygapophyseal face craniomedially, while the postzygapophyses face caudolaterally. The caudal vertebrae have neural spines that join together with postzygapophyses, as to form a caudal process which ends cranial to the midpoint of the following vertebrae. The reduction of the size of the postzygapophyses coincides with the reduction of the prezygapophyses. Unlike other ankylosaurids, Chuanqilong lacked a tail club as it lacks the modified handle-like vertebrae in the distal portion of the tail. The coracoid is not co-ossified with the

scapula The scapula (plural scapulae or scapulas), also known as the shoulder blade, is the bone that connects the humerus (upper arm bone) with the clavicle (collar bone). Like their connected bones, the scapulae are paired, with each scapula on eith ...

, which might represent an ontogenetic trait as it is also known in other juvenile ankylosaur specimens. The scapula blade has a rhomboid-like outline, with a dorsal margin that is straight and a ventral margin that is concave. The narrowest point of the scapular blade is towards the head of the

. The ventral edge of the scapula lacks a distinct enthesis, which may also represent an ontogenetic trait. The glenoid fossa has an oval outline and is large. The

is short, with a large deltopectoral crest. The proximal end of the femur has a width that is much greater than the width of the distal end. The radial condyle is more prominent than the medial ulna condyle, while the lateral epicondylar ridge is underdeveloped. The

ulna The ulna (''pl''. ulnae or ulnas) is a long bone found in the forearm that stretches from the elbow to the smallest finger, and when in anatomical position, is found on the medial side of the forearm. That is, the ulna is on the same side of t ...

has a wedge-shaped

olecranon The olecranon (, ), is a large, thick, curved bony eminence of the ulna, a long bone in the forearm that projects behind the elbow. It forms the most pointed portion of the elbow and is opposite to the cubital fossa or elbow pit. The olecranon ...

process, as in other immature ankylosaur specimens and may represent an ontogenetic characteristic. The radius is slender and rod-like, with a distal end that is wider transversely than the proximal end of the

radius In classical geometry, a radius (plural, : radii) of a circle or sphere is any of the line segments from its Centre (geometry), center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', ...

. Only the left manus is known, which consists of four

metacarpals In human anatomy, the metacarpal bones or metacarpus form the intermediate part of the skeletal hand located between the phalanges of the fingers and the carpal bones of the wrist, which forms the connection to the forearm. The metacarpal bones ar ...

that are all slender in appearance. Out of all the metacarpals, metacarpal III is the longest while metacarpal IV is the shorter. The other metacarpals are sub-equal in length. The most robust metacarpal is metacarpal I, while metacarpals II and IV are the slenderest. The distal and proximal ends if all the metacarpals are expanded. The ungual

phalanges The phalanges (singular: ''phalanx'' ) are digital bones in the hands and feet of most vertebrates. In primates, the thumbs and big toes have two phalanges while the other digits have three phalanges. The phalanges are classed as long bones. ...

have a triangular outline with a sharp point, while the ventral surfaces are flattened. Chuanqilong_ilium_and_ischia

The preacetabular process of the ilium is long and is rotated towards the middle, while the postacetabular process is rotated in apposition. The preacetabular process diverges sideways from the

vertebral column The vertebral column, also known as the backbone or spine, is part of the axial skeleton. The vertebral column is the defining characteristic of a vertebrate in which the notochord (a flexible rod of uniform composition) found in all chordate ...

and has a straight side margin. The postacetabular process has a subtriangular outline and is shorter than the acetabulum. The pubic peduncle has a profile that is sub-rounded and developed, while the ischial peduncle is undeveloped. The

ischium The ischium () form ...

is long, lacks an obturator process and has a slender shaft that curves slightly towards the underside. The mid-shaft region of the ischium is narrow and widens towards the distal end before tapering further distally. The ischium has a proximal end that is straight in side view, unlike the convex and fan-like ischium of ''Ankylosaurus'' and the concave proximal ischia of ''

Struthiosaurus ''Struthiosaurus'' (Latin ''struthio'' = ostrich + Greek ''sauros'' = lizard) is a genus of nodosaurid dinosaurs, from the Late Cretaceous period (Santonian-Maastrichtian) of Austria, Romania, France and Hungary in Europe. ...

''. As typical with other ankylosaurs, the

is both robust and straight. The

femoral head The femoral head (femur head or head of the femur) is the highest part of the thigh bone (femur). It is supported by the femoral neck. Structure The head is globular and forms rather more than a hemisphere, is directed upward, medialward, and a l ...

forms an articular surface that is circular. The femur possesses both the cranial and greater trochanters, which are separated from the femoral head by a tightening. The cranial trochanter is separated from the greater trochanter, which is seen in juvenile ankylosaur specimens but not in most adult ankylosaurs. However, this may rather represent a

plesiomorphic In phylogenetics, a plesiomorphy ("near form") and symplesiomorphy are synonyms for an ancestral character shared by all members of a clade, which does not distinguish the clade from other clades. Plesiomorphy, symplesiomorphy, apomorphy, and ...

trait of ankylosaurids, as well as a trait under ontogenetic control in some ankylosaurs, due to the cranial trochanter being also present in some nodosaurids. Present on the femur is a shallow cranial intercondylar fossa. ''Chuanqilong'' has a similar ratio of humerus to femur length to ''Ankylosaurus'', but lower that that of other juvenile ankylosaur specimens and ''

Hungarosaurus ''Hungarosaurus tormai'' is a herbivorous nodosaurid ankylosaur from the Upper Cretaceous ( Santonian) Csehbánya Formation of the Bakony Mountains of western Hungary. It is the most completely known ankylosaur from the Cretaceous of Europe. ...

''. The

tibia The tibia (; ), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outside of the tibia); it conn ...

is shorter than the femur and robust, with the proximal end having a transverse expansion that is weaker then that of the distal end of the tibia. Slightly shorter than the tibia is the fibula, which is slender and has a shaft that is oval in cross-section, as well as being relatively equal in size. The right foot preserves metatarsals II, III, and IV in articulation. The longest and most robust metatarsal is metatarsal III, while metatarsals II and IV are both sub-equal in length. All of the preserved metatarsals have proximal and distal ends that are expanded. The unguals have a sub-triangular outline with distal ends that are sub-rounded and are similar to that of '' Dyoplosaurus''.

Armour

The only preserved cervical half ring of ''Chuanqilong'' consists of a connecting band that is fused into a single plate, but is compressed towards the dorsal and ventral sides and is also segmented into four sections. Of these sections, the right three have a subrectangular outline and are arched upwards, while the left section has a subtriangular profile and tapers caudolaterally. The

shoulder The human shoulder is made up of three bones: the clavicle (collarbone), the scapula (shoulder blade), and the humerus (upper arm bone) as well as associated muscles, ligaments and tendons. The articulations between the bones of the shoulder mak ...

region preserves two osteoderm plates that are large, flat, thickened and have a subrectangular outline. The largest of these osteoderm plates is twice the length of the other and are both similar to the osteoderms of cervical half ring but may also represent separate cervical osteoderm plates. Between the proximal end of the left ulna and radius is a small triangular osteoderm that has a wide base and tapers distally. Present near the left ischium is an oval osteoderm that is sharply keeled along the midline. Preserved over the entirety of the body are a diverse range of osteoderms and ossicles that are small and irregular.

Classification

Liaoningosaurus-Beijing_Museum_of_Natural_History

Han ''et al.'' (2014) originally found ''Chuanqilong'' to be a basal ankylosaurid that was

sister taxon In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...

to '' Liaoningosaurus''. The authors noted that only two unambiguous

synapomorphies In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to ha ...

supported its close relationship to ''Liaoningosaurus'', which are the presence of an antorbital fossa and a ventrally oriented scapula glenoid. The authors also noted that, although both taxa are represented by juvenile specimens and are sister taxa, ''Chuanqilong'' can be differentiated from ''Liaoningosaurus'' based on a number of characteristics such as the differences in the metatarsus to metacarpus length ratio and the morphology of the cheek tooth crown. Cladistic analyses conducted by Arbour & Currie (2015) recovered ''Chuanqilong'' as either being within a

polytomy An internal node of a phylogenetic tree is described as a polytomy or multifurcation if (i) it is in a rooted tree and is linked to three or more child subtrees or (ii) it is in an unrooted tree and is attached to four or more branches. A tr ...

with other basal ankylosaurids or as sister taxon to ''

Cedarpelta ''Cedarpelta'' is a extinct genus of basal ankylosaurid dinosaur from Utah that lived during the Late Cretaceous period ( Cenomanian to lower Turonian stage, 98.2 to 93 Ma) in what is now the Mussentuchit Member of the Cedar Mountain Formati ...

'', a position also recovered by Arbour ''et al.'' (2016). Analyses conducted by Arbour & Evans (2017), Zheng ''et al.'' (2018) and Park ''et al.'' (2019) similarly placed ''Chuanqilong'' within a polytomy with other basal ankylosaurids, although the inclusion of certain taxa such as '' Aletopelta'' within the internal node varied. Rivera-Sylva ''et al.'' (2018) also recovered it within a polytomy in a strict consensus tree, but it was also recovered it as sister taxon to ''Cedarpelta'' in a 50% majority rule tree. Contrary to other analyses, Frauenfelder ''et al.'' (2022) found ''Chuanqilong'' to be within a clade including ''Liaoningosaurus'' and ''Cedarpelta'' outside of Ankylosauridae and Nodosauridae. In 2019, an abstract suggested the possibility that ''Chuanqilong'' and ''Liaoningosaurus'' may represent the same species but at different ontogenetic stages. Below is a reproduced phylogenetic analysis from Arbour & Currie (2015).

Paleoenvironment

The remains of ''Chuanqilong'' were uncovered from the

of the Jehol Group. The formation is composed of

mudstones Mudstone, a type of mudrock, is a fine-grained sedimentary rock whose original constituents were clays or muds. Mudstone is distinguished from ''shale'' by its lack of fissility (parallel layering).Blatt, H., and R.J. Tracy, 1996, ''Petrology.'' ...

siltstones Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility.Blatt ''et al.'' 1980, p ...

shales Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especially ...

sandstones Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) ...

and

tuffs Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is considered tuff, while rock con ...

, and overlies the

Yixian Formation The Yixian Formation (; formerly transcribed as Yihsien Formation) is a geological formation in Jinzhou, Liaoning, People's Republic of China, that spans the late Barremian and early Aptian stages of the Early Cretaceous. It is known for its exq ...

. Recent secondary ion mass spectrometry (SIMS) zircon U-Pb analyses suggest that the formation dates to the late

stages of the

, ca. 122.0–118.9 Ma. Both the Yixian and Jiufotang Formations represent freshwater lacustrine environments that lacked

rivers A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at the end of its course without reaching another body of wate ...

as well as many other variable features of freshwater settings, and would have fluctuated seasonally between

semi-arid A semi-arid climate, semi-desert climate, or steppe climate is a dry climate sub-type. It is located on regions that receive precipitation below potential evapotranspiration, but not as low as a desert climate. There are different kinds of semi- ...

and mesic conditions. The Jiufotang Formation experienced infrequent

volcanic activity Volcanism, vulcanism or volcanicity is the phenomenon of eruption of molten rock (magma) onto the surface of the Earth or a solid-surface planet or moon, where lava, pyroclastics, and volcanic gases erupt through a break in the surface called a ...

, while the younger Yixian Formation had more frequent activity. A combination of regional volcanism and the presence of many shallow

lakes A lake is an area filled with water, localized in a basin, surrounded by land, and distinct from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, although, like the much large ...

allowed the exceptional preservation of fossils and the preservation of integument impressions,

cartilage Cartilage is a resilient and smooth type of connective tissue. In tetrapods, it covers and protects the ends of long bones at the joints as articular cartilage, and is a structural component of many body parts including the rib cage, the neck ...

and

keratin Keratin () is one of a family of structural fibrous proteins also known as ''scleroproteins''. Alpha-keratin (α-keratin) is a type of keratin found in vertebrates. It is the key structural material making up Scale (anatomy), scales, hair, Nail ...

. A variety of forms of Euornithines (such as '' Mengciusornis'', '' Piscivoravis'', '' Parahongshanornis'', and '' Yanornis'') and Enantiornithines (such as '' Cuspirostrisornis'',Zhou Z. and Wang Y. (2010). "Vertebrate diversity of the Jehol Biota as compared with other lagerstätten." ''Science China: Earth Sciences'', 53(12): 1894–1907.

'' Longipteryx'', ''

Rapaxavis ''Rapaxavis'' a genus of enantiornithine bird. It has been found in the Jiufotang Formation in Liaoning, People's Republic of China. In 2006 a specimen was reported, discovered by Pan Lijun at Xiaioyugou near the town of Lianhe, and referred ...

'', '' Sinornis'',Sereno, P. C., & Rao, C. (1992). "Early evolution of avian flight and perching: New evidence from the lower Cretaceous of China". ''Science'', 255(5046), 845. and '' Yuanchuavis'') are present in the Jiufotang Formation. Numerous

pterosaurs Pterosaurs (; from Greek ''pteron'' and ''sauros'', meaning "wing lizard") is an extinct clade of flying reptiles in the order, Pterosauria. They existed during most of the Mesozoic: from the Late Triassic to the end of the Cretaceous (228 to 6 ...

are also known from the formation including the chaoyangopterids ''Chaoyangopterus'', ''Eoazhdarcho'', ''Jidapterus'' and ''Shenzhoupterus'', the ctenochasmatid ''Forfexopterus'', the anhanguerids ''Guidraco'' and Liaoningopterus, the lonchodraconid ''Ikrandraco'', the Ornithocheiromorpha, istiodactyliforms ''Hongshanopterus'', ''Liaoxipterus'',Dong, Z., and Lü, J. (2005). A New Ctenochasmatid Pterosaur from the Early Cretaceous of Liaoning Province. ''Acta Geologica Sinica'' 79(2):164-167. ''Linlongopterus'' and ''Nurhachius'',Zhou X., Pêgas R.V., Leal M.E.C. & Bonde N. 2019
"''Nurhachius luei'', a new istiodactylid pterosaur (Pterosauria, Pterodactyloidea) from the Early Cretaceous Jiufotang Formation of Chaoyang City, Liaoning Province (China) and comments on the Istiodactylidae."
''PeerJ'' 7:e7688Xiaolin Wang, Kellner, A.W.A., Zhou Zhonghe, and de Almeida Campos, D. (2005). Pterosaur diversity and faunal turnover in Cretaceous terrestrial ecosystems in China. ''Nature'' 437:875–879. the tapejarid ''Sinopterus'', the anurognathid ''Vesperopterylus'' and the indeterminate pterodactyloid ''Pangupterus''. Other fauna present include the jeholornithiforms ''Jeholornis'' and ''Kompsornis'', the omnivoropterygids ''Omnivoropteryx''Czerkas, S. A. & Ji, Q. (2002). "A preliminary report on an omnivorous volant bird from northeast China." ''In'': Czerkas, S. J. (editor): ''Feathered Dinosaurs and the origin of flight. The Dinosaur Museum Journal'' 1: 127-135
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/ref> and ''Sapeornis'',Zhou, Zhonghe & Zhang, Fucheng (2003): Anatomy of the primitive bird ''Sapeornis chaoyangensis'' from the Early Cretaceous of Liaoning, China. ''Canadian Journal of Earth Sciences'' 40(5): 731–747. (HTML abstract) the oviraptorosaur ''Similicaudipteryx'', the dromaeosaurid ''Microraptor'', the tyrannosauroid ''Sinotyrannus'', the ''ceratopsian'' ''Psittacosaurus'', the mammaliamorphs ''Fossiomanus'' and ''Liaoconodon'', and the choristoderes ''Philydrosaurus'', ''Ikechosaurus''A new species of ''Ikechosaurus'' (Reptilia: Choristodera) from the Jiufutang Formation (Early Cretaceous) of Chifeng City, Inner Mongolia
LÜ J.-C.; Kobayashi Y.; Li Z.-G. and ''Liaoxisaurus''.

References

{{Taxonbar, from=Q17516418 Early Cretaceous dinosaurs of Asia Jiufotang fauna Cretaceous China Fossils of China Fossil taxa described in 2014 Ornithischian genera