''Liushusaurus'' is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

lizard Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia alt ...

described by

Susan E. Evans Susan E. Evans is British palaeontologist and herpetologist. She is the author or co-author of over 100 peer-reviewed papers and book chapters. She received a BSc in Zoology at Bedford College in 1974, and in 1977 a PhD in vertebrate palaeon ...

and

Yuan Wang The Yuan Wang-class of tracking ships () are used for tracking and support of satellite and intercontinental ballistic missiles by the People's Liberation Army Strategic Support Force of the People's Republic of China (PRC). It is important to no ...

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 Lower may refer to: *Lower (surname) *Lower Township, New Jersey *Lower Receiver (firearms) *Lower Wick Lower Wick is a small hamlet located in the county of Gloucestershire, England. It is situated about five miles south west of Dursley, eight ...

aged Yixian Formation of Northeast

China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...

. ''Liushusaurus'' is one of eight lizards that are known and have been named from the Yixian Formation, part of the diverse Jehol Biota

ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...

Etymology

Evans and Wang coined 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 or ''Liushusaurus'' from the

Chinese Chinese can refer to: * Something related to China * Chinese people, people of Chinese nationality, citizenship, and/or ethnicity **''Zhonghua minzu'', the supra-ethnic concept of the Chinese nation ** List of ethnic groups in China, people of va ...

word ''liushu'' and the

Greek language Greek ( el, label=Modern Greek, Ελληνικά, Elliniká, ; grc, Ἑλληνική, Hellēnikḗ) is an independent branch of the Indo-European family of languages, native to Greece, Cyprus, southern Italy (Calabria and Salento), southern Al ...

word '. ''Liushu'' which translates as "willow tree", is derived from ''Liutiao'', ''willow leaf'', and refers to Liutiaogou, ''willow leaf valley'', where the fossils were found. The Greek word ' (') translates to "lizard". Evans and Wang chose the

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

from a combination of the

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

words ''acanthus'' meaning "spine" and ''cauda'' meaning tail. This combination is in allusion to the scale structure found along the tail.

Description

''Liushusaurus'' was a medium-sized, stocky lizard with a wide body and short legs. Several fossils preserve the outline of individuals and show that they were robustly built, with a thick tail and legs. The body outline extends beyond the ribcage to show a wide midsection as well. Several fossil specimens show a high degree of preservation, with intact scales, pigmentation, claw sheaths, cartilage, and small bones. The orbitospenoids are present in one specimen as two small crescent-shaped bones. These bones support the cartilage and membrane that makes up the

braincase In human anatomy, the neurocranium, also known as the braincase, brainpan, or brain-pan is the upper and back part of the skull, which forms a protective case around the brain. In the human skull, the neurocranium includes the calvaria or skul ...

, and are rarely preserved in fossil lizards. Postcloacal or hemipenial bones are also known, which are part of the hemipenis in male individuals. The dorsal scales that cover the back are much smaller than the ventral scales that cover the underside, which are rhomboidal and overlap each other. The bases of the ventral scales are darker than their edges. They are darkest toward the middle of the belly and nearest the midline. The ventral scales decrease in size toward the neck and limbs, becoming rounder and less dark. Going down the tail, the scales get longer and narrower and start to taper. Their coloration gives them the appearance of small spines. The dorsal scales are round and granular, each less than half a millimetre in diameter. Scales on the head are also granular, unlike the platelike scales of

scincomorph Scincomorpha is an infraorder and clade of lizards including skinks (Scincidae) and their close relatives. These include the living families Cordylidae (girdled lizards), Gerrhosauridae (plated lizards), and Xantusiidae (night lizards), as wel ...

and anguimorph lizards. An area of the skull not covered by scales indicates the presence of the tympanum, the external hearing structure of lizards. ''Liushusaurus'' is known from several well preserved fossils representing eight individuals. These individuals range in age from near-hatchling to adult. All specimens preserve 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 connects ...

and

fibula The fibula or calf bone is a leg bone on the lateral side of the tibia, to which it is connected above and below. It is the smaller of the two bones and, in proportion to its length, the most slender of all the long bones. Its upper extremity is ...

of the lower leg, and the length of these bones ranges from to . This indicates a wide range of

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 st ...

variation. Large individuals have smaller feet in relation to their hindlimbs than small individuals, while small individuals have proportionally shorter forelimbs relative to their hindlimbs. ''Liushusaurus'' may have been sexually dimorphic, as specimens have been found with possible post-

cloaca In animal anatomy, a cloaca ( ), plural cloacae ( or ), is the posterior orifice that serves as the only opening for the digestive, reproductive, and urinary tracts (if present) of many vertebrate animals. All amphibians, reptiles and birds, a ...

l bones that would indicate they are males. These bones are seen in some living lizards such as

gekkota Geckos are small, mostly carnivorous lizards that have a wide distribution, found on every continent except Antarctica. Belonging to the infraorder Gekkota, geckos are found in warm climates throughout the world. They range from . Geckos ar ...

ns. Specimens with these bones tend to be the largest individuals, suggesting that males may have been larger than females.

Classification

Based on a

phylogenetic In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

analysis that was conducted along with its initial description, ''Liushusaurus'' is closely related to

Scleroglossa Scleroglossa is a group of lizards that includes geckos, autarchoglossans (scincomorphs, anguimorphs, and varanoids), and amphisbaenians. Scleroglossa is supported by phylogenetic analyses that use morphological features (visible anatomical featu ...

, a group that includes

gecko Geckos are small, mostly carnivorous lizards that have a wide distribution, found on every continent except Antarctica. Belonging to the infraorder Gekkota, geckos are found in warm climates throughout the world. They range from . Geckos ar ...

skink Skinks are lizards belonging to the family Scincidae, a family in the infraorder Scincomorpha. With more than 1,500 described species across 100 different taxonomic genera, the family Scincidae is one of the most diverse families of lizards. Ski ...

worm lizard Amphisbaenia (called amphisbaenians or worm lizards) is a group of usually legless squamates, comprising over 200 extant species. Amphisbaenians are characterized by their long bodies, the reduction or loss of the limbs, and rudimentary eyes. As ...

monitor lizard Monitor lizards are lizards in the genus ''Varanus,'' the only extant genus in the family Varanidae. They are native to Africa, Asia, and Oceania, and one species is also found in the Americas as an invasive species. About 80 species are recogn ...

s, and

snakes Snakes are elongated, limbless, carnivorous reptiles of the suborder Serpentes . Like all other squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales. Many species of snakes have skulls with several more joi ...

. However, it is classified as a more

basal Basal or basilar is a term meaning ''base'', ''bottom'', or ''minimum''. Science * Basal (anatomy), an anatomical term of location for features associated with the base of an organism or structure * Basal (medicine), a minimal level that is nec ...

member of the

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

Scincogekkonomorpha, which includes Scleroglossa and all taxa more closely related to Scleroglossa than to Iguania. This encompasses several other extinct taxa, such as ''

Ardeosaurus ''Ardeosaurus'' is an extinct genus of basal lizards, known from fossils found in the Late Jurassic Solnhofen Plattenkalk of Bavaria, southern Germany. It was originally thought to have been a species of ''Homeosaurus''. ''Ardeosaurus'' was ...

'' and ''

Bavarisaurus ''Bavarisaurus'' ('Bavarian lizard') is an extinct genus of basal squamate found in the Solnhofen limestone near Bavaria, Germany.Late Jurassic Solnhofen limestone of

Germany Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwe ...

. Together, these extinct taxa are considered

stem Stem or STEM may refer to: Plant structures * Plant stem, a plant's aboveground axis, made of vascular tissue, off which leaves and flowers hang * Stipe (botany), a stalk to support some other structure * Stipe (mycology), the stem of a mushro ...

scleroglossans. Out of all of these taxa, ''Liushusaurus'' is most closely related to Scleroglossa, being the

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 t ...

of the clade. However, the results of the phylogenetic analysis were uncertain because of difficulties in distinguishing stem scleroglossans based on their morphology. Below is a cladogram modified from the phylogenetic analysis of Evans and Wang, 2010:

Paleobiology

''Liushusaurus'' probably had a similar lifestyle to living Malagasy

s of the genus ''

Uroplatus ''Uroplatus'' is a genus of gecko Geckos are small, mostly carnivorous lizards that have a wide distribution, found on every continent except Antarctica. Belonging to the infraorder Gekkota, geckos are found in warm climates throughout t ...

'' or

Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...

n cordylid lizards of the genus ''

Platysaurus ''Platysaurus'' is a genus of lizards, commonly known as flat lizards for their flat backs, in the family Cordylidae. Geographic range All species in the genus ''Platysaurus'' live in isolated populations in southern Africa. They are found in ...

''. Both types of lizards have flattened bodies. Like living lizards with this body shape, ''Liushusaurus'' had a relatively short

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 eithe ...

and short suprascapular

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 an ...

above it. It also had long

rib In vertebrate anatomy, ribs ( la, costae) are the long curved bones which form the rib cage, part of the axial skeleton. In most tetrapods, ribs surround the chest, enabling the lungs to expand and thus facilitate breathing by expanding the ches ...

s toward its backside that did not curve greatly. ''Liushusaurus'' may have been more similar in appearance to the living Chuckwalla (''Sauromalus'') of

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

, which has a broad rather than flat body. ''Liushusaurus'' likely climbed on rough surfaces such as rocks and vegetation, aided by long, sharp claws, relatively symmetrical feet, long forelimbs, and well-developed scales on the undersides of its digits called tubercular plantar digital scales. The flattened body may have been useful in

thermoregulation Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different. A thermoconforming organism, by contrast, simply adopts the surrounding temperature ...

, providing a greater surface area for heat from the sun to reach while basking. It may also have allowed ''Liushusaurus'' to fit into small crevices like the living ''Platysaurus''. Alternatively, the depressed body shape could have helped ''Liushusaurus'' control falls like the living ''

Leiolepis ''Leiolepis'', commonly known as butterfly lizards or butterfly agamas ( th, แย้), are group of agamid lizards. They are native to Peninsular Malaysia, Thailand, Myanmar, Laos, Cambodia, Indonesia, Ryukyu Islands (Japan), Vietnam, and Hai ...

'', or Butterfly lizard. It may also have helped disguise the outline of the body as in ''Uroplatus''. The small, conical teeth of ''Liushusaurus'' suggest that it ate

insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pairs ...

s and other small invertebrates. Many species of dragonflies have been described from the Yixian Formation, as well as gnats,

mayflies Mayflies (also known as shadflies or fishflies in Canada and the upper Midwestern United States, as Canadian soldiers in the American Great Lakes region, and as up-winged flies in the United Kingdom) are aquatic insects belonging to the orde ...

beetle Beetles are insects that form the order Coleoptera (), in the superorder Endopterygota. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 400,000 describ ...

s, and many other insects, and may have been part of the diet of ''Liushusaurus''.

Paleoecology

DalinghesaurusLongidigitus-PaleozoologicalMuseumOfChina-May23-08

''Liushusaurus'' lived alongside several other lizards, the most common of which from the

Jehol Group The Jehol Biota includes all the living organisms – the ecosystem – of northeastern China between 133 and 120 million years ago. This is the Lower Cretaceous ecosystem which left fossils in the Yixian Formation and Jiufotang Formation. These ...

are '' Yabeinosaurus'' and ''

Dalinghosaurus ''Dalinghosaurus'' (often incorrectly spelled "Dalinghesaurus") is an extinct genus of lizards, first described in 1998 by S.A. Ji of the Peking University Department of Geology. The type species is ''Dalinghosaurus longidigitus''.Ji, S.A. (1998 ...

''. Several other genera have been described, mostly from juvenile specimens. These include '' Jeholacerta'', '' Liaoningolacerta'', and ''

Xianglong ''Xianglong'' (meaning "flying dragon" in Chinese) is a genus of Cretaceous lizard discovered in the Zhuanchengzi, near Yizhou, Yixian, Liaoning Province of China.

''. ''Jeholacerta'' is known only from a skin impression and several skull impressions, while ''Liaoningolacerta'' has been described from a single specimen belonging to a very young individual. ''Xianglong'' is known from better material, and elongate ribs indicate it was a gliding lizard.

References

{{Taxonbar, from=Q6654095 Prehistoric animals of China Cretaceous lizards Fossil taxa described in 2010 Taxa named by Wang Yuan Taxa named by Susan E. Evans