Liushusaurus
Encyclopedia
Liushusaurus, is an extinct 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 named lizards known from the that have been named from the Yixian Formation, part of the diverse Jehol Biota
ecosystem
.
name or Liushusaurus from the Chinese
word liushu and the Greek language
word sauros. 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 sauros (σαύρος) translates to "lizard". Evans and Wang chose the specific name
from a combination of the Latin
words acanthus meaning "spine" and cauda meaning tail. This combination is in allusion to the scale structure found along the tail.
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, 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
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
and fibula of the lower leg, and the length of these bones ranges from 3.62 millimetre (0.14251968503937 in) to 11.85 millimetre (0.466535433070866 in). This indicates a wide range of ontogenetic 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
l bones that would indicate they are males. These bones are seen in some living lizards such as gekkota
ns. Specimens with these bones tend to be the largest individuals, suggesting that males may have been larger than females.
, a group that includes gecko
s, skink
s, worm lizards, monitor lizard
s, and snakes. However, it is classified as a more basal
member of the clade
Scincogekkonomorpha, which includes Scleroglossa and all taxa more closely related to Scleroglossa than to Iguania
. This encompasses several other extinct taxa, such as Ardeosaurus
and Bavarisaurus
from the Late Jurassic
Solnhofen limestone
of Germany
. Together, these extinct taxa are considered stem scleroglossans. Out of all of these taxa, Liushusaurus is most closely related to Scleroglossa, being the sister taxon 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:
Liushusaurus probably had a similar lifestyle to living Malagasy
gecko
s of the genus Uroplatus
or Africa
n cordylid
lizards of the genus Platysaurus
. Both types of lizards have flattened bodies. Like living lizards with this body shape, Liushusaurus had a relatively short scapula
and short suprascapular cartilage
above it. It also had long rib
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
, 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
, 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
, 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
s and other small invertebrates. Many species of dragonflies have been described from the Yixian Formation, as well as gnat
s, mayflies, beetle
s, and many other insects, and may have been part of the diet of Liushusaurus.
Liushusaurus lived alongside several other lizards, the most common of which from the Jehol Group
are Yabeinosaurus
and Dalinghosaurus
. Several other genera have been described, mostly from juvenile specimens. These include Jeholacerta, Liaoningolacerta, and Xianglong
. 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.
Squamata
Squamata, or the scaled reptiles, is the largest recent order of reptiles, including lizards and snakes. Members of the order are distinguished by their skins, which bear horny scales or shields. They also possess movable quadrate bones, making it possible to move the upper jaw relative to the...
described by Susan E. Evans
Susan E. Evans
Susan E. Evans is British paleontologist and herpetologist. She is the author or co-author of over 100 peer-reviewed papers and book chapters....
and Yuan Wang
Yuan Wang
Yuan Wang is a Paleontologist and has been the director of the Paleozoological Museum of China since 2004. This natural history museum is affiliated to the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences .He is a Research Professor at IVPP and...
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
Yixian Formation
The Yixian Formation is a geological formation in Jinzhou, Liaoning, People's Republic of China, that spans 11 million years during the early Cretaceous period...
of Northeast China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
. Liushusaurus is one of eight named lizards known from the that have been named from the Yixian Formation, part of the diverse Jehol Biota
Jehol Biota
The Jehol Biota includes all the living organisms - the ecosystem - of northeastern China between 133 to 120 million years ago. This is the Lower Cretaceous ecosystem which left fossils in the Yixian Formation and Jiufotang Formation. It is also believed to have left fossils in the Sinuiju series...
ecosystem
Ecosystem
An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....
.
Etymology
Evans and Wang coined the genericGenus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
name or Liushusaurus from the Chinese
Chinese language
The Chinese language is a language or language family consisting of varieties which are mutually intelligible to varying degrees. Originally the indigenous languages spoken by the Han Chinese in China, it forms one of the branches of Sino-Tibetan family of languages...
word liushu and the Greek language
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
word sauros. 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 sauros (σαύρος) translates to "lizard". Evans and Wang chose the specific name
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
from a combination of the Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
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, and are rarely preserved in fossil lizards. Postcloacal or hemipenial bones are also known, which are part of the hemipenis
Hemipenis
A hemipenis is one of a pair of intromittent organs of male squamates .Hemipenes are usually held inverted, within the body, and are everted for reproduction via erectile tissue, much like that in the human penis. Only one is used at a time, and some evidence indicates males alternate use between...
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
Scincomorpha is an infraorder of saurians....
and anguimorph
Anguimorpha
Anguimorphs of the infraorder Anguimorpha include the anguids , monitor lizards, the extinct mosasaurs, and helodermatids . The infraorder was named by Fürbringer in 1900 to include all autarchoglossans closer to Varanus and Anguis than Scincus...
lizards. An area of the skull not covered by scales indicates the presence of the tympanum
Tympanum (zoology)
The tympanum is an external hearing structure in animals such as frogs, toads, insects, and mammals, to name a few.-Anurans:In frogs and toads, it is located just behind the eye. It does not actually process sound waves; it simply transmits them to the amphibian's inner ear, which is protected...
, 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
Tibia
The tibia , shinbone, or shankbone is the larger and stronger of the two bones in the leg below the knee in vertebrates , and connects the knee with the ankle bones....
and fibula of the lower leg, and the length of these bones ranges from 3.62 millimetre (0.14251968503937 in) to 11.85 millimetre (0.466535433070866 in). This indicates a wide range of ontogenetic 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
Cloaca
In zoological anatomy, a cloaca is the posterior opening that serves as the only such opening for the intestinal, reproductive, and urinary tracts of certain animal species...
l bones that would indicate they are males. These bones are seen in some living lizards such as gekkota
Gekkota
Gekkota is an infraorder of reptiles in the suborder Scleroglossa, comprising all geckos and the limbless Pygopodidae. The legless lizards of the family Dibamidae are also referred to as blind lizards but recent molecular phylogenies suggest they are not gekkotans.Gekkota are a suborder of...
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 analysis that was conducted along with its initial description, Liushusaurus is closely related to ScleroglossaScleroglossa
Scleroglossa is the previously recognized suborder of Squamata that contains the geckos, anguids, worm lizards, monitor lizards, such as helodermatids, skinks and snakes. The name is derived from the Greek, skleros, meaning hard and glossa, meaning tongue.Traditionally, Squamata has been divided...
, a group that includes gecko
Gecko
Geckos are lizards belonging to the infraorder Gekkota, found in warm climates throughout the world. They range from 1.6 cm to 60 cm....
s, skink
Skink
Skinks are lizards belonging to the family Scincidae. Together with several other lizard families, including Lacertidae , they comprise the superfamily or infraorder Scincomorpha...
s, worm lizards, monitor lizard
Monitor lizard
Monitor lizards are usually large reptiles, although some can be as small as in length. They have long necks, powerful tails and claws, and well-developed limbs. Most species are terrestrial, but arboreal and semiaquatic monitors are also known...
s, and snakes. However, it is classified as a more basal
Basal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
member of the clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
Scincogekkonomorpha, which includes Scleroglossa and all taxa more closely related to Scleroglossa than to Iguania
Iguania
Iguania is the suborder of Squamata that contains the iguanas, chameleons, agamids, and "New World lizards" such as anoles and Phrynosomatidae...
. This encompasses several other extinct taxa, such as Ardeosaurus
Ardeosaurus
Ardeosaurus is an extinct genus of basal lizard , from the Late Jurassic of Germany.Ardeosaurus was distantly related to modern geckos, and had a similar physical appearance. It was around long, with a flattened head and large eyes...
and Bavarisaurus
Bavarisaurus
Bavarisaurus is an extinct genus of basal lizard found in the Solnhofen limestone near Bavaria, Germany. It is best known from a fossil skeleton found in the stomach region of a Compsognathus, a small theropod dinosaur....
from the Late Jurassic
Late Jurassic
The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 161.2 ± 4.0 to 145.5 ± 4.0 million years ago , which is preserved in Upper Jurassic strata. In European lithostratigraphy, the name "Malm" indicates rocks of Late Jurassic age...
Solnhofen limestone
Solnhofen limestone
The Solnhofen Plattenkalk is a Jurassic Konservat-Lagerstätte that preserves a rare assemblage of fossilized organisms, including highly detailed imprints of soft bodied organisms such as sea jellies...
of Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
. Together, these extinct taxa are considered stem scleroglossans. Out of all of these taxa, Liushusaurus is most closely related to Scleroglossa, being the sister taxon 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
Cladogram
A cladogram is a diagram used in cladistics which shows ancestral relations between organisms, to represent the evolutionary tree of life. Although traditionally such cladograms were generated largely on the basis of morphological characters, DNA and RNA sequencing data and computational...
modified from the phylogenetic analysis of Evans and Wang, 2010:
Paleobiology
Madagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...
gecko
Gecko
Geckos are lizards belonging to the infraorder Gekkota, found in warm climates throughout the world. They range from 1.6 cm to 60 cm....
s of the genus Uroplatus
Uroplatus
Uroplatus is a genus of geckos commonly referred to as Flat or Leaf-tailed Geckos. All the comprising species are endemic to Madagascar or nearby islands, such as Nosy Be, where they are found in primary and secondary forests.-Etymology:...
or Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
n cordylid
Cordylidae
Cordylidae is a family of small to medium sized lizards that occur in southern and eastern Africa. They are commonly known as "Girdled", Spinytail lizards or Girdle-tail lizards. Girdled lizards are diurnal and insectivorous...
lizards of the genus Platysaurus
Platysaurus
Platysaurus is a genus of lizards in the Cordylidae family, known as flat lizards for their flat backs. All species live in isolated populations in southern Africa.-Description:...
. Both types of lizards have flattened bodies. Like living lizards with this body shape, Liushusaurus had a relatively short scapula
Scapula
In anatomy, the scapula , omo, or shoulder blade, is the bone that connects the humerus with the clavicle ....
and short suprascapular cartilage
Cartilage
Cartilage is a flexible connective tissue found in many areas in the bodies of humans and other animals, including the joints between bones, the rib cage, the ear, the nose, the elbow, the knee, the ankle, the bronchial tubes and the intervertebral discs...
above it. It also had long rib
Rib
In vertebrate anatomy, ribs are the long curved bones which form the rib cage. In most vertebrates, ribs surround the chest, enabling the lungs to expand and thus facilitate breathing by expanding the chest cavity. They serve to protect the lungs, heart, and other internal organs of the thorax...
s toward its backside that did not curve greatly. Liushusaurus may have been more similar in appearance to the living Chuckwalla
Chuckwalla
Chuckwallas are large lizards found primarily in arid regions of the southwestern United States and northern Mexico. Some are found on coastal islands...
(Sauromalus) of North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
, 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
Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different...
, 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
Leiolepis, commonly known as Butterfly Lizards , are group of agamid lizards of which very little is known. They are native to Thailand, Burma, Laos, Cambodia, Indonesia, and Vietnam...
, 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
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
s and other small invertebrates. Many species of dragonflies have been described from the Yixian Formation, as well as gnat
Gnat
A gnat is any of many species of tiny flying insects in the Dipterid suborder Nematocera, especially those in the families Mycetophilidae, Anisopodidae and Sciaridae.In British English the term applies particularly to Nematocerans of the family Culicidae...
s, mayflies, beetle
Beetle
Coleoptera is an order of insects commonly called beetles. The word "coleoptera" is from the Greek , koleos, "sheath"; and , pteron, "wing", thus "sheathed wing". Coleoptera contains more species than any other order, constituting almost 25% of all known life-forms...
s, and many other insects, and may have been part of the diet of Liushusaurus.
Paleoecology
Jehol Biota
The Jehol Biota includes all the living organisms - the ecosystem - of northeastern China between 133 to 120 million years ago. This is the Lower Cretaceous ecosystem which left fossils in the Yixian Formation and Jiufotang Formation. It is also believed to have left fossils in the Sinuiju series...
are Yabeinosaurus
Yabeinosaurus
Yabeinosaurus is an extinct genus of basal lizard thought to be about 30 cm long. It is known from China.A 120 million year old fossil of a Yabeinosaurus was discovered in 2011, and represents the oldest fossil of a pregnant, live-bearing lizard yet discovered....
and Dalinghosaurus
Dalinghosaurus
Dalinghosaurus is an extinct genus of lizards, first described in 1998 by S.A. Ji of the Peking University Department of Geology...
. Several other genera have been described, mostly from juvenile specimens. These include Jeholacerta, Liaoningolacerta, and Xianglong
Xianglong
Xianglong is a genus of Cretaceous lizard discovered in the Liaoning Province of China. It is known from LPM 000666, a single complete skeleton with skin impressions. The specimen comes from the Barremian-age Lower Cretaceous Yixian Formation, near Yizhou...
. 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.