- Agilisaurus
Taxobox|
name = "Agilisaurus"
fossil_range =Middle Jurassic
image_caption = "Agilisaurus louderbacki"
regnum =Animal ia
phylum =Chordata
classis =Sauropsida
superordo =Dinosauria
ordo =Ornithischia
subordo = uncertain
genus = "Agilisaurus"
species = "A. louderbacki"
binomial = "Agilisaurus louderbacki"
binomial_authority = Peng, 1990"Agilisaurus" (pronEng|ˌædʒ
ɪlɪˈsɔrəs; 'agile lizard') is agenus ofornithischia ndinosaur from the MiddleJurassic Period of what is noweastern Asia . The name is derived from theLatin "agilis" meaning 'agile' and the Greek "sauros" meaning 'lizard', and refers to the agility suggested by its lightweight skeleton and long legs. Itstibia (lower leg bone) was longer than itsfemur (upper leg bone), which indicates that it was an extremely fastbipedal runner, using its long tail for balance, although it may have been gotten down on all fours when browsing for food. It was a smallherbivore , about 1.2 meters (4 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.There is one named
species ("A. louderbacki"), named after Dr. George Louderback, an Americangeologist and the first to recognize dinosaurfossils from theSichuan Province ofChina in 1915. Both genus andtype species were named by Chinesepaleontologist Peng Guangzhou 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 outside the city ofZigong , in the Chinese province of Sichuan, including "Agilisaurus", as well as"Xuanhanosaurus ", "Shunosaurus ", and "Huayangosaurus ". This quarry preserves sediment from theLower Shaximiao Formation (sometimes called "Xiashaximiao") which ranges from theBathonian throughCallovian stages of theMiddle Jurassic 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 (Peng 1990).Several recent studies, including
cladistic analyses, find "Agilisaurus" to be the most basal member of the groupEuornithopoda , which includes all ornithopods morederived than the family Heterodontosauridae (Weishampel et al. 2003; Norman et al. 2004).However, heterodontosaurs are not universally considered to be ornithopods and have been considered more closely related to the suborder
Marginocephalia , which includesceratopsia ns andpachycephalosaur s. In one recent cladistic analysis, "Agilisaurus" was found in a position basal to heterodontosaurs in the branch leading to Marginocephalia (Xu et al. 2006)."Agilisaurus" has been recovered in other positions as well, including as an ornithischian basal to both ornithopods and marginocephalians (Barrett et al. 2005; Butler 2005; Butler et al. 2008).
econd Species?
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 it 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" (Barrett et al. 2005). Several studies agree that this species is slightly more derived than "Agilisaurus" (Norman et al. 2004; Barrett et al. 2005; Butler 2005). Both "Yandusaurus" and "Hexinlusaurus" were also found in the Dashanpu Quarry.References
*Barrett, P.M., Butler, R.J., & Knoll, F. 2005. Small-bodied ornithischian dinosaurs from the Middle Jurassic of Sichuan, China. "Journal of Vertebrate Paleontology" 25(4): 823-834.
*Butler, R.J. 2005. The ‘fabrosaurid’ ornithischian dinosaurs of the Upper Elliot Formation (Lower Jurassic) of South Africa and Lesotho. "Zoological Journal of the Linnean Society" 145: 175–218.
*cite journal |last=Butler |first=Richard J. |coauthors=Upchurch, Paul; and Norman, David B. |title=The phylogeny of the ornithischian dinosaurs|journal=Journal of Systematic Palaeontology |volume=6 |issue=1 |year=2008 |pages=1–40 |doi=10.1017/S1477201907002271
*Norman, D.B., Sues, H-D., Witmer, L.M., & Coria, R.A. 2004. Basal Ornithopoda. In: Weishampel, D.B., Dodson, P., & Osmolska, H. (Eds.) "The Dinosauria" (2nd Edition). Berkeley: University of California Press. Pp. 393-412.
*Peng G. 1990. [A new small ornithopod ("Agilisaurus louderbacki" gen. et sp. nov.) from Zigong, China] . ["Newsletter of the Zigong Dinosaur Museum"] 2: 19-27. [in Chinese]
*Peng G. 1992. [Jurassic ornithopod "Agilisaurus louderbacki" (Ornithopoda: Fabrosauridae) from Zigong, Sichuan, China] . "Vertebrata PalAsiatica" 30: 39-51. [in Chinese]
*Weishampel, D.B., Jianu, C.-M., Csiki, Z., & Norman, D.B. Osteology and phylogeny of "Zalmoxes" (n.g.), an unusual euornithopod dinosaur from the latest Cretaceous of Romania. "Journal of Systematic Palaeontology" 1: 65–123.
*Xu X., Forster, C.A., Clark, J.M., & Mo J. 2006. A basal ceratopsian with transitional features from the Late Jurassic of northwestern China. "Proceedings of the Royal Society B: Biological Sciences". doi:10.1098/rspb.2006.3566 [published online]External links
* [http://dino.lm.com/images/display.php?id=1800 "Agilisaurus" skeleton] at the [http://www.dino.lm.com Dinosauricon]
* [http://www.dinodata.org/index.php?option=com_content&task=view&id=6059&Itemid=67 "Agilisaurus" at Dinodata]
* [http://www.nhm.ac.uk/jdsml/nature-online/dino-directory/detail.dsml?Genus=Agilisaurus Agilisaurus] in the [http://www.nhm.ac.uk/jdsml/nature-online/dino-directory/ Dino Directory]
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