''Agilisaurus'' (; 'agile lizard') is a
genus of
ornithischia
Ornithischia () is an extinct order of mainly herbivorous dinosaurs characterized by a pelvic structure superficially similar to that of birds. The name ''Ornithischia'', or "bird-hipped", reflects this similarity and is derived from the Greek s ...
n
dinosaur from the Middle
Jurassic Period of what is now
eastern Asia
East Asia is the eastern region of Asia, which is defined in both Geography, geographical and culture, ethno-cultural terms. The modern State (polity), states of East Asia include China, Japan, Mongolia, North Korea, South Korea, and Taiwan. ...
. It was about 3.5–4 ft (1.2-1.7
m) long, 2 ft (0.6 m) in height and 40 kg in weight.
It has leaf-shaped teeth that were well-adapted to their abrasive, plant-based diets. Most surprisingly, the wavy enamel of the teeth of ''A. louderbacki'' and all other
ornithopods, presumably to make it more resistant to wear, was previously thought to be exclusive to the
hadrosaurs.
[ This is also the case for '']Changchunsaurus parvus
''Changchunsaurus'' (meaning " Changchun lizard") is an extinct genus of small herbivorous dinosaur from Early Cretaceous deposits of Gongzhuling, Jilin, China. It is the first named dinosaur genus from Jilin.
Description
''Changchunsaurus'' ...
''.[Jun Chen, Aaron R. H. LeBlanc, Liyong Jin, Timothy Huang, Robert R. Reisz. Tooth development, histology, and enamel microstructure in Changchunsaurus parvus: Implications for dental evolution in ornithopod dinosaurs. PLOS ONE, 2018; 13 (11): e0205206 DOI: 10.1371/journal.pone.0205206]
Description
Its tibia (lower leg bone) 207.0 mm in length, was longer than its femur (upper leg bone) 199.0 mm in length, which indicates that it was an extremely fast bipedal runner, using its long tail for balance, although it may have walked on all fours when browsing for food.[ It was a small ]herbivore
A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpart ...
, about 2 meters (6.5 feet) in length, and like all ornithischians, it had a beak-like structure on the ends of both upper and lower jaws to help it crop plant material.
Because it lacks tail-stiffening interwoven bony struts, some paleontologists think it may have been a burrow
An Eastern chipmunk at the entrance of its burrow
A burrow is a hole or tunnel excavated into the ground by an animal to construct a space suitable for habitation or temporary refuge, or as a byproduct of locomotion. Burrows provide a form of sh ...
dweller.[
]
Discovery and history
There is one named species (''A. louderbacki''), named after Dr. George Louderback, an American
American(s) may refer to:
* American, something of, from, or related to the United States of America, commonly known as the "United States" or "America"
** Americans, citizens and nationals of the United States of America
** American ancestry, pe ...
geologist and the first to recognize dinosaur fossils
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved in ...
from the Sichuan Province of 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 ...
in 1915. The holotype, which is the only known specimen, was discovered in 1984, during the construction of the Zigong Dinosaur Museum. Both genus and type species were named by Chinese paleontologist Peng Guangzhou
Peng may refer to:
* Peng (surname) (彭), a Chinese name
* Peng (state) (大彭), a state during the late Shang dynasty
* Peng (mythology) (鵬), a legendary Chinese creature
* ''Peng!'', 1992 album by Stereolab
* ''PENG!'', a 2005 comic
* P.Eng. ...
in very brief fashion in 1990, then described in further detail by Peng in 1992.
A single complete skeleton of ''A. louderbacki'' is known to science, one of the most complete small ornithischian skeletons ever found. Only a few parts of its left fore limb and hind limb are missing, and those can be reconstructed from their counterparts on the right side.[
This skeleton was actually discovered during the construction of the Zigong Dinosaur Museum, in which it is now housed. This museum features many dinosaurs recovered from the famous ]Dashanpu Quarry
The Shaximiao Formation () is a Middle to Late Jurassic aged geological formation in Sichuan, China, most notable for the wealth of dinosaurs fossils that have been excavated from its strata. The Shaximiao Formation is exposed in and around the ...
outside the city of Zigong, in the Chinese province of Sichuan, including ''Agilisaurus'', as well as'' Xuanhanosaurus
''Xuanhanosaurus'' (meaning "Xuanhan lizard") is a genus of theropod dinosaur that lived during the Middle Jurassic of China, around 167.7 to 161.2 million years ago.
Discovery
The type species ''Xuanhanosaurus qilixiaensis'' was named by Don ...
'', '' Shunosaurus'', and '' Huayangosaurus''. This quarry preserves sediment from the Lower Shaximiao Formation (sometimes called "Xiashaximiao") which ranges from the Bathonian through Callovian stages of the Middle Jurassic
The Middle Jurassic is the second epoch of the Jurassic Period. It lasted from about 174.1 to 163.5 million years ago. Fossils of land-dwelling animals, such as dinosaurs, from the Middle Jurassic are relatively rare, but geological formations co ...
Period, or from about 168 to 161 million years ago.
Taxonomy
Despite its completeness, ''Agilisaurus'' has been placed in many different positions in the ornithischian family tree. It was originally placed in the family Fabrosauridae, which is no longer considered valid by most paleontologists.[
Several recent studies, including cladistic analyses, find ''Agilisaurus'' to be the most ]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 group Euornithopoda, which includes all ornithopods more derived
Derive may refer to:
* Derive (computer algebra system), a commercial system made by Texas Instruments
* ''Dérive'' (magazine), an Austrian science magazine on urbanism
*Dérive, a psychogeographical concept
See also
*
*Derivation (disambiguatio ...
than the family Heterodontosauridae.
However, heterodontosaurs are not universally considered to be ornithopods and have been considered more closely related to the suborder Marginocephalia, which includes ceratopsia
Ceratopsia or Ceratopia ( or ; Greek: "horned faces") is a group of herbivorous, beaked dinosaurs that thrived in what are now North America, Europe, and Asia, during the Cretaceous Period, although ancestral forms lived earlier, in the Jurassic. ...
ns and pachycephalosaur
Pachycephalosauria (; from Greek παχυκεφαλόσαυρος for 'thick headed lizards') is a clade of ornithischian dinosaurs. Along with Ceratopsia, it makes up the clade Marginocephalia. With the exception of two species, most pachyc ...
s. In one recent cladistic analysis, ''Agilisaurus'' was found in a position basal to heterodontosaurs in the branch leading to Marginocephalia.[
''Agilisaurus'' has been recovered in other positions as well, including as an ornithischian basal to both ornithopods and marginocephalians.]
In his more thorough 1992 description, Peng added a new species to the genus ''Agilisaurus''.[ This species had previously been known as '' Yandusaurus multidens''. Because this species did not belong in the genus ''Yandusaurus'' and due to similarities with ''A. louderbacki'', it was assigned the name ''Agilisaurus multidens''.][
Other scientists were not convinced that this species belonged to either ''Yandusaurus'' or ''Agilisaurus'', and in 2005, it was once again reassigned, this time to its own newly created genus. It is now known as '' Hexinlusaurus multidens''.] Several studies agree that this species is slightly more derived than ''Agilisaurus''.[
]
Etymology
The name is derived from the Latin "''agilis"'' meaning 'agile' and the Greek "''sauros"'' meaning 'lizard', and refers to the agility suggested by its lightweight skeleton and long legs.
The species epithet, ''louderbacki'', honors the late U.S. geologist Dr. George D. Louderback the first to discover fossils within the Sichuan Basin in 1915
Events
Below, the events of World War I have the "WWI" prefix.
January
* January – British physicist Sir Joseph Larmor publishes his observations on "The Influence of Local Atmospheric Cooling on Astronomical Refraction".
*January 1 ...
.
Paleobiology
Comparisons between the scleral ring
Sclerotic rings are rings of bone found in the eyes of many animals in several groups of vertebrates, except for mammals and crocodilians. They can be made up of single bones or multiple segments and take their name from the sclera. They are bel ...
s of ''Agilisaurus'' and modern birds and reptiles suggest that it may have been diurnal, unlike larger herbivorous dinosaurs that were inferred to be cathemeral, active throughout the day at short intervals.
References
External links
Agilisaurus
in the
Dino Directory
NHM.ac.uk.
{{Taxonbar, from=Q131319
Fossil taxa described in 1990
Middle Jurassic dinosaurs of Asia
Ornithischian genera
Paleontology in Sichuan