Description
The holotype specimen of Xianglong was 15.5 centimetres (6.1 in) long, 9.5 centimetres (3.7 in) of which was tail, although the describers say it was probably a juvenile. This is indicated by the unossified carpals and poorly-ossified tarsals. Metacarpal IV is shorter than the other metacarpals, and pedal digit V is greatly elongated. The radius and ulna are distally divergent. The body is covered in small, granular scales, showing little size variation. Xianglong had slightly curved claws, indicating that it was arboreal. The ribs of the animal, which functioned as gliding organs, were found in a half-open position, which indicates a post-mortem relaxation of the folded wing. So far this is the only known fossil gliding lizard, though there are other unrelated animals that also use their ribs to glide. [2]
Gliding ability
Xianglong is one of the few creatures that glide using their ribs. Other creatures, such as the flying squirrel and the Malabar flying frog, Rhacophorus malabaricus , have a different membrane attachment, toes to toes or limb to limb. Two creatures use the same way to glide, the present day Flying Lizard (genus Draco , Latin for dragon) and Triassic fossil reptiles such as Kuehneosaurus , but the Triassic look-alikes lived over 100 million years before Xianglong. Despite the 11-centimetre (4.3 in) "rib-span", the lizard might have been quite agile in the air, possibly to escape the feathered dinosaurs that coexisted with it. [2]
Xu Xing, a Chinese paleontologist and one of the describers of Xianglong, states that it is possible that it could have glided as far as half a football field, much farther than that of the modern Draco. [1]
Draco is a genus of agamid lizards that are also known as flying lizards, flying dragons or gliding lizards. These lizards are capable of gliding flight via membranes that may be extended to create wings (patagia), formed by an enlarged set of ribs. They are arboreal insectivores.
Sinornithosaurus is a genus of feathered dromaeosaurid dinosaur from the early Cretaceous Period of the Yixian Formation in what is now China. It was the fifth non–avian feathered dinosaur genus discovered by 1999. The original specimen was collected from the Sihetun locality of western Liaoning. It was found in the Jianshangou beds of the Yixian Formation, dated to 124.5 million years ago. Additional specimens have been found in the younger Dawangzhangzi bed, dating to around 122 million years ago.
A number of animals are capable of aerial locomotion, either by powered flight or by gliding. This trait has appeared by evolution many times, without any single common ancestor. Flight has evolved at least four times in separate animals: insects, pterosaurs, birds, and bats. Gliding has evolved on many more occasions. Usually the development is to aid canopy animals in getting from tree to tree, although there are other possibilities. Gliding, in particular, has evolved among rainforest animals, especially in the rainforests in Asia where the trees are tall and widely spaced. Several species of aquatic animals, and a few amphibians and reptiles have also evolved this gliding flight ability, typically as a means of evading predators.
Kuehneosaurus is an extinct genus of Late Triassic kuehneosaurid reptile known from the Late Triassic of the Penarth Group of southwest England and the Steinmergel Group of Luxembourg. Temperature at this stage and region would have ranged from 28 to 35 °C. It was named by P. L. Robinson in 1962 in honour of paleontologist Walther Kühn, and the type and only species is Kuehneosaurus latus. Measuring 72 centimetres long, it had "wings" formed from ribs which jutted out from its body by as much as 14.3 cm, connected by a membrane which allowed it to slow its descent when jumping from trees. It is a member of a family of extinct gliding reptiles, the Kuehneosauridae, within a larger living group the Lepidosauromorpha, which contain modern lizards and tuatara.
Sharovipteryx is a genus of early gliding reptiles containing the single species Sharovipteryx mirabilis. It is known from a single fossil and is the only glider with a membrane surrounding the pelvis instead of the pectoral girdle. This lizard-like reptile was found in 1965 in the Madygen Formation, Dzailauchou, on the southwest edge of the Fergana Valley in Kyrgyzstan, in what was then the Asian part of the U.S.S.R. dating to the middle-late Triassic period. The Madygen horizon displays flora that put it in the Upper Triassic. An unusual reptile, Longisquama, was also found there.
Coelurosauravus is an extinct genus of gliding reptile, known from the Late Permian of Madagascar. Like other members of the family Weigeltisauridae, members of this genus possessed long, rod-like ossifications projecting outwards from the body. These bony rods were not extensions of the ribs but were instead a feature unique to weigeltisaurids. It is believed that during life, these structures formed folding wings used for gliding flight, similar to living gliding Draco lizards.
Icarosaurus is an extinct genus of kuehneosaurid reptile from the Late Triassic Lower Lockatong Formation of New Jersey. It is closely related to lizards and the tuatara. Based on a partial skeleton missing part of the tail, some ribs, a hand, and parts of the legs, it was a small animal, about 10 centimeters (4 in) long from the skull to the hips. Like its relative Kuehneosaurus, it was able to glide short distances using 'wings' consisting of highly elongated ribs covered with skin. These gliding membranes would have had a convex upper surface and a concave lower surface, thus creating a simple airfoil structure well-suited to gliding. This method of gliding is also seen in Coelurosauravus and the modern Draco, neither of which are closely related to Icarosaurus.
Weigeltisaurus is an extinct genus of weigeltisaurid reptile from the Late Permian Kupferschiefer of Germany and Marl Slate of England. It has a single species, originally named as Palaechamaeleo jaekeli in 1930 and later assigned the name Weigeltisaurus jaekeli in 1939, when it was revealed that Palaeochamaeleo was a preoccupied name. A 1987 review by Evans and Haubold later lumped Weigeltisaurus jaekeli under Coelurosauravus as a second species of that genus. A 2015 reassessment of skull morphology study substantiated the validity of Weigeltisaurus and subsequent authors have used this genus. Like other Weigeltisaurids, they possessed long rod-like bones that radiated from the trunk that were likely used to support membranes used for gliding, similar to extant Draco lizards.
Sinocalliopteryx is a genus of carnivorous compsognathid theropod dinosaurs from the Lower Cretaceous Yixian Formation of China.
Flying dragons is the common name of gliding lizards in the genus Draco, particularly the species Draco volans.
Mecistotrachelos is an extinct genus of gliding reptile from the Late Triassic of Virginia. It is generally interpreted as an archosauromorph, distantly related to crocodylians and dinosaurs. The type and only known species is M. apeoros. This specific name translates to "soaring longest neck", in reference to its gliding habits and long neck. This superficially lizard-like animal was able to spread its lengthened ribs and glide on wing-like membranes. Mecistotrachelos had a much longer neck than other gliding reptiles of the Triassic such as Icarosaurus and Kuehneosaurus. It was probably an arboreal insectivore.
Yixianopterus is a pterodactyloid pterosaur genus from the Barremian-Aptian-age Lower Cretaceous Yixian Formation of Liaoning, China. It is known from a single specimen, holotype JZMP-V-12, housed at the Benxi Geological Museum. This specimen was modified before acquisition, with much of the skull being fabricated. The Jinggangshan bedding in which the specimen was found is basaltic with siliciclastic sediments. Many organisms associated with this layer of the Yixian Formation are aquatic, indicating a marine environment with much volcanic activity.
Archaeorhynchus is a genus of beaked avialan stem-birds from the early Cretaceous period. A fossil of its only known species, Archaeorhynchus spathula, was first reported in 2005 by Zhou & Zhang to have been found in Yixian Formation rocks at Yixian, Liaoning province, China, showing a well-preserved and essentially complete skeleton. Two more complete specimens were found in Lower Cretaceous deposits of Jianchang, Liaoning, northeastern China, preserving new anatomical information. These deposits are 120 million years old, whereas the original specimen was 125 million years old, meaning the age range for this species is 125-120Ma.
Kuehneosauridae is an extinct family of small, lizard-like gliding diapsids known from the Triassic period of Europe and North America.
Weigeltisauridae is a family of gliding neodiapsid reptiles that lived during the Late Permian, between 259.51 and 251.9 million years ago. Fossils of weigeltisaurids have been found in Madagascar, Germany, Great Britain, and Russia. They are characterized by long, hollow rod-shaped bones extending from the torso that probably supported wing-like membranes. Similar membranes are also found in several other extinct reptiles such as kuehneosaurids and Mecistotrachelos, as well as living gliding lizards, although each group evolved these structures independently.
Liushusaurus is an extinct genus of lizard described by Susan E. Evans and Yuan Wang in 2010. The genus has a single species, Liushusaurus acanthocaudata, and is known from eight fossils, several of which preserve soft tissue detail. The specimens were found in the Lower Cretaceous aged Yixian Formation of Northeast China. Liushusaurus is one of eight lizards that are known and have been named from the Yixian Formation, part of the diverse Jehol Biota ecosystem.
Afairiguana avius is an extinct iguanid lizard known from a nearly complete and articulated skeleton discovered in rocks of the Early Eocene-aged Green River Formation of Wyoming, United States. As of the initial description, the skeleton represents the oldest complete iguanian from the Western Hemisphere, and is the oldest representative of the extant iguanid family of anoles, Polychrotidae.
Draco mindanensis, commonly known as the Mindanao flying dragon or Mindanao flying lizard, is a lizard species endemic to the Philippines. Characterized by a dull grayish brown body color and a vivid tangerine orange dewlap, this species is one of the largest of the genus Draco. It is diurnal, arboreal, and capable of gliding.
Ozimek is a genus of sharovipterygid archosauromorph reptile, known from Late Triassic deposits in Poland and closely related to the Kyrgyzstani Sharovipteryx. It contains one species, O. volans, named in 2016 by Jerzy Dzik and Tomasz Sulej. Like Sharovipteryx, Ozimek had long, slender limbs with the hindlimbs longer than the forelimbs; the hindlimbs likely supported gliding membranes as fossilized in Sharovipteryx. Another unusual characteristic was the shoulder girdle, where the massive coracoids formed a shield-like structure covering the bottom of the shoulder region that would have limited mobility. In other respects, such as its long neck, it was a typical member of the non-natural grouping Protorosauria. Phylogenetic analysis has indicated that it, possibly along with Sharovipteryx, may have been an unusual member of the protorosaur group Tanystropheidae, although further study of its anatomy is needed to resolve its precise relationships.
Zhongjianosaurus is a genus of dromaeosaurid belonging to the Microraptoria. Believed to hail from the Yixian Formation, specifically the middle of the Jehol Biota, it is the smallest known microraptorine thus far discovered and one of the smallest non-avian theropod dinosaurs.
