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{{Automatic taxobox
{{speciesbox
| fossil_range = [[Late Cretaceous]], {{fossilrange|90|earliest=98|latest=83}}
| fossil_range = [[Late Cretaceous]], {{fossilrange|97|83}}
| image = Erlikosaurus skull and foot.jpg
| image = Erlikosaurus skull and foot.jpg
| image_caption = Skull and foot of the holotype specimen
| image_caption = Skull and right pes of the holotype specimen '''MPC-D 100/111'''
| image_upright = 1.2
| genus = Erlikosaurus
| display_parents = 2
| parent_authority = [[Altangerel Perle|Perle]], [[1980 in paleontology|1980]]
| species = andrewsi
| taxon = Erlikosaurus
| authority = Perle, 1980
| authority = Barsbold & Perle, 1980
| type_species = {{extinct}}'''''Erlikosaurus andrewsi'''''
| type_species_authority = Barsbold & Perle, 1980
}}
}}


'''''Erlikosaurus''''' is a [[genus]] of herbivorous [[theropod]] [[dinosaur]] from the late [[Cretaceous Period]], belonging to the [[Therizinosaur]]idae. Its fossils, a skull and some post-cranial fragments, were found in the [[Bayan Shireh Formation]] of [[Mongolia]], dating to around 90 million years ago.<ref name="ageofdinosaurserlikosaurus"/>
'''''Erlikosaurus''''' (meaning "Erlik's lizard") is a [[genus]] of [[therizinosaur]] [[theropod]] [[dinosaur]] that lived in [[Asia]] during the [[Late Cretaceous]] period. Its fossils, a skull and some post-cranial fragments, were found in the [[Bayan Shireh Formation]] of [[Mongolia]], dating to around 97 million and 83 million years ago. ''Erlikosaurus'' represents the second therizinosaurian taxa from this Mongolian formation (alongside ''[[Enigmosaurus]]'' and ''[[Segnosaurus]]'') with the most complete skull among other relatives of this peculiar family of dinosaurs.

⚫
==Discovery and naming==
[[File:Cretaceous-aged dinosaur fossil localities of Mongolia.PNG|thumb|left|300px|Fossil localities in Mongolia. Locality of ''Erlikosaurus'' in '''Bayshin Tsav''', at Area C]]
[[File:Erlikosaurus Skeleton Reconstruction.jpg|270px|thumb|Known elements from holotype '''MPC-D 100/111''']]
The [[holotype]], '''MPC-D 100/111''', was found in layers from the Bayshin Tsav locality on the [[Bayan Shireh Formation]], consisting of a well preserved skull with lower jaws, some cervical vertebrae fragments and remains of the forelimb and hindlimb; these findings were made during a Soviet-Mongolian expedition in the [[Ömnögovi Province]] in 1972.<ref name=Barsbold1980>{{cite journal|last1=Barsbold|first1=R.|last2=Perle|first2=A.|title=Segnosauria, a new suborder of carnivorous dinosaurs|journal=Acta Palaeontologica Polonica|date=1980|volume=25|issue=2|pages=190-192|url=https://www.app.pan.pl/archive/published/app25/app25-187.pdf}}</ref><ref name=PerleA1981>{{cite journal|last1=Perle|first1=A.|title=Novyy segnozavrid iz verkhnego mela Mongolii|trans-title=New Segnosauridae from the Upper Cretaceous of Mongolia|journal=Transactions of the Joint Soviet-Mongolian Paleontological Expedition|date=1981|volume=15|pages=50-59|url=https://paleoglot.org/files/Perle%2081.pdf|language=Russian}}</ref> Eight years later, the [[genus]] and [[type species]], ''Erlikosaurus andrewsi'', was named and described (although very briefly) by paleontologists [[Rinchen Barsbold]] and [[Altangerel Perle]] in [[1980 in paleontology|1980]], however, Barsbold was not indicated as the name-giver of this particular species. The [[Genus#Use|generic name]], ''Erlikosaurus'', was taken from that of the demon king '''''[[Erlik]]''''', from Turko-Mongolian [[mythology]] and the [[Greek language|Greek]] '''''σαῦρος''''' (sauros, meaning lizard). The [[Specific name (zoology)|specific name]], ''andrewsi'', is in honour to the American paleontologist [[Roy Chapman Andrews]], who was the leader of the American Asiatic Expeditions from 1922 to 1930.<ref name=Barsbold1980/>

Confusingly, in 1981 Perle again named and described the species as if it were new, but this time in more detail and spelling the generic name as a [[Romanization|Latinised]] "Erlicosaurus".<ref name=PerleA1981/> It is today widely accepted by most authors that the original name, ''Erlikosaurus'', is valid. At the time of its discovery it was the only known therizinosaur (then called segnosaurs<ref name=Perle1979>{{cite journal|last1=Perle|first1=A.|title=Segnosauridae — novoe semejstvo teropod iz pozdnego mela Mongolii|trans-title=Segnosauridae — a new family of theropods from the Late Cretaceous of Mongolia|journal=Transactions of the Joint Soviet-Mongolian Paleontological Expedition|date=1979|volume=8|pages=45-55|url=http://paleoglot.org/files/Perle%2079.pdf|language=Russian}}</ref>) for which a complete skull had been discovered, this helped shed light on a puzzling and poorly known group of dinosaurs. It still represents the most completely known therizinosaurian skull.<ref name=Zanno2010>{{cite journal|first1=L. E.|last1=Zanno|year=2010|title=A taxonomic and phylogenetic re-evaluation of Therizinosauria (Dinosauria: Maniraptora)|journal=Journal of Systematic Palaeontology|volume=8|issue=4|pages=503–543|doi=10.1080/14772019.2010.488045}}</ref><ref name=Lautenschlager2012>{{cite journal|last1=Stephan|first1=L.|last2=Emily|first2=J. R.|last3=Perle|first3=A.|last4=Lindsay|first4=E. Z.|last5=Lawrence|first5=M. W.|title=The Endocranial Anatomy of Therizinosauria and Its Implications for Sensory and Cognitive Function|journal=PLoS ONE|year=2012|volume=7|issue=12|pages=e52289|doi=10.1371/journal.pone.0052289|pmid=23284972|pmc=3526574}}</ref>

In 2010, [[Gregory S. Paul]] challenged the validity of this taxon, arguing that ''Erlikosaurus'' may be the same animal as ''[[Enigmosaurus|Enigmosaurus mongoliensis]]'' (named in 1983<ref name=Barsbold1983>{{cite journal|last1=Barsbold|first1=R.|authorlink=Rinchen Barsbold|title=Хищные динозавры мела Монголии|trans-title=Carnivorous dinosaurs from the Cretaceous of Mongolia|journal=Transactions of the Joint Soviet-Mongolian Paleontological Expedition|volume=19|page=107|year=1983|url=http://www.geokniga.org/bookfiles/geokniga-hishchnye-dinozavry-mela-mongolii.pdf|language=Russian}} [https://paleoglot.org/files/Barsbold_83.pdf Translated paper]</ref>), since the latter was found in the same [[geologic formation]], and was only known from pelvic remains, whereas the [[pelvis]] of ''Erlikosaurus'' is unknown; this would make ''Enigmosaurus'' a [[junior synonym]] of ''Erlikosaurus''.<ref name=Paul2010/> However, since the ''Enigmosaurus'' hip did not resemble that of ''[[Segnosaurus]]'' as closely as would be expected for the ''Segnosaurus''-like ''Erlikosaurus'' remains, and there is a considerable size difference, paleontologist Rinchen Barsbold disputed the alleged synonymy.<ref name=Dodson1993>{{cite book|last1=Dodson|first1=P.|title=The Age of Dinosaurs|chapter=Erlikosaurus|publisher=Publications International, LTD|date=1993|page=142|isbn=0-7853-0443-6}}</ref> Additional to this, ''Erlikosaurus'' and ''Enigmosaurus'' are known from upper and lower beds, respectively.<ref name=Clark1994/><ref name=Barsbold1983/><ref name=Tsogtbaatar2019/> Consequently, ''Enigmosaurus'' and ''Erlikosaurus'' are generally still considered separate genera.<ref>{{cite journal|last1=Hartman|first1=S.|last2=Mortimer|first2=M.|last3=Wahl|first3=W. R.|last4=Lomax|first4=D. R.|last5=Lippincott|first5=J.|last6=Lovelace|first6=D. M.|title=A new paravian dinosaur from the Late Jurassic of North America supports a late acquisition of avian flight|journal=PeerJ|date=2019|volume=7|pages=e7247|doi=10.7717/peerj.7247|pmid=31333906|pmc=6626525}}</ref>


==Description==
==Description==
[[File:Beipiaosaurus-Paleozoological Museum of China.jpg|thumb|left|Partial forelimb of the [[Basal (phylogenetics)|basal]] therizinosaur ''[[Beipiaosaurus]]'' with impressions of [[Feathered dinosaur#Primitive feather types|feather-like structures]], [[Paleozoological Museum of China]]]]
[[File:Erlikosaurus feathered.jpg|thumb|left|Restoration]]
[[File:Erlikosaurus feathered.jpg|thumb|[[Paleoart|Life restoration]] of ''Erlikosaurus'']]
''Erlikosaurus'' were [[therizinosaur]]s, a strange group of theropods that ate plants instead of meat, and that had backward-facing [[pubis (bone)|pubis]]es like [[ornithischia]]ns. Also like ornithischians, their jaws were tipped by a broad rounded bony beak useful for cropping off plants.<ref name="ageofdinosaurserlikosaurus"/> Behind the beak, separated by an hiatus, there were per side twenty-three small straight coarsely serrated teeth in the [[maxilla]].<ref name=Zanno2010/> The [[dentary]] of the lower jaw had more teeth: thirty-one for a total of one hundred eight. The bony nostrils of ''Erlikosaurus'' were very large and elongated. The braincase was swollen at the back by pneumatised bone. Scientists now know some therizinosaurs were feathered, so it is likely that ''Erlikosaurus'' were as well. ''Erlikosaurus'' had exceptionally long slender claws on their feet, with a bone core of up to ten centimetres, the purpose of which is unclear; G.S. Paul surmised they were used for self-defence.<ref name=Paul2010/>
The [[holotype]] is fragmentary, consisting of a exceptionally well preserved [[skull]], a virtually complete right [[Pes (anatomy)|pes]] only lacking the proximal end of [[metatarsals]] II, III and IV, and an almost complete left [[humerus]]. Other remains include some fragmentary [[cervical vertebrae]], however, the count is not specified and they were not illustrated.<ref name=Barsbold1980/><ref name=PerleA1981/> Apparently, in the original description a left pes was claimed to be part of the holotype<ref name=Barsbold1980/>, however, this statement has not been mentioned again.<ref name=PerleA1981/><ref name=Clark1994>{{cite journal|last1=Clark|first1=J. M.|last2=Perle|first2=A.|last3=Norell|first3=M.|title=The skull of Erlicosaurus andrewsi, a Late Cretaceous "Segnosaur" (Theropoda, Therizinosauridae) from Mongolia|journal=American Museum Novitates|date=1994|volume=3115|pages=1-39|url=http://digitallibrary.amnh.org/handle/2246/3712}}</ref><ref name=Zanno2010/><ref name=Lautenschlager2012/> It is currently now know that some therizinosaurs were [[Feather#Feathered dinosaurs|feathered]] based on the preserved [[Fossil#Adpression (compression-impression)|skin impressions]] of ''[[Beipiaosaurus]]'', so it is [[Phylogenetic bracketing|likely]] that ''Erlikosaurus'' was feathered as well.<ref name=Xu1999>{{cite journal|last1=Xu|first1=X.|last2=Tang|first2=Z.|last3=Wang|first3=X. A.|title=A therizinosauroid dinosaur with integumentary structures from China|journal=Nature|year=1999|volume=339|pages=350–354|doi=10.1038/20670}}</ref> As the genus is only known from very fragmentary material, it has been problematic to determine the size of ''Erlikosaurus'', especially as most of the [[vertebral column]] of the holotype is missing. The holotype skull length is {{convert|25|cm|mm|abbr=on}} long; the humerus is approximately {{convert|30|cm|mm|abbr=on}} long, this indicates a very small individual. ''Erlikosaurus'' may have been more lightly built than close relative ''[[Segnosaurus]]'' with an estimated adult size of {{convert|6|m|ft|abbr=on}} long.<ref name=Dodson1993/> Other estimates are lower: in 2010 [[Gregory S. Paul]] gave a length of 4.5 metres and a weight of {{convert|500|kg|lb|abbr=on}}.<ref name=Paul2010>{{cite book|last1=Paul|first1=G. S.|title=The Princeton Field Guide to Dinosaurs|publisher=Princeton University Press|date=2010|page=159|isbn=978-0-6911-3720-9}}</ref> Nevertheless, [[Thomas Holtz]] in 2012 estimated its length at {{convert|3.4|m|ft|abbr=on}} long with a weight between {{convert|227|to|454|kg|lb|abbr=on}}.<ref name=Holtz2012>{{cite book|last1=Holtz|first1=T. R.|last2=Rey|first2=L. V.|title=Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages|date=2007|publisher=Random House}} [https://www.geol.umd.edu/~tholtz/dinoappendix/HoltzappendixWinter2011.pdf Genus List for Holtz 2012] [https://www.geol.umd.edu/~tholtz/dinoappendix/appendix.html Weight Information]</ref> Stephan et al. 2012 used theropod-specific equations to estimate the body mass of ''Erlikosaurus'' and other therizinosaurs. However, since the femur is unknown, they used bivariate regression analyses on log-transformed data; the results ended up on a femoral length of {{convert|44.33|cm|mm|abbr=on}} and a weight of {{convert|173.7|kg|lb|abbr=on}}. Given the uncertainities of these estimates, they established an overall mass range between {{convert|150|to|250|kg|lb|abbr=on}}.<ref name=Lautenschlager2012/>
===Skull===
[[File:Reconstructed beak and skull of Erlikosaurus.jpeg|thumb|left|Restored skull of ''Erlikosaurus'' with (A) conservative keratinous beak, and (B) extensive keratinous beak]]
The most studied element from ''Erlikosaurus'' is its articulated, complete skull. The snout is moderately elongated<ref name=Barsbold1980/>, with a [[premaxilla]] featuring elongated nasal [[Process (anatomy)|processes]]. A fine, vertical lamina of [[bone]] is connected rostrally to the medial margin of the premaxilla, indicating that when the animal was alive, a [[cartilaginous]] [[Nasal septum|internasal septum]] was present. Additional to this, the premaxilla features lateral and medial [[foramina]] that are connected by a complex system of [[Blood vessel|vascular canals]], which pervades the structure of the premaxilla and is probably associated with the sensory branches of the neurovasculature and [[ophthalmic nerve]] supporting the [[Beak#Rhamphotheca|rhamphotheca]] (beak). The [[maxilla]] is triangular in shape and preserves 24 [[Dental alveolus|alveoli]], the [[teeth]] are [[homodont]] with coarse [[Denticle (tooth feature)|serrations]]. The [[dentary]] is wedge-shaped elongated and preserves 31 alveoli. In dorsal view, it is U-shaped and dorsoventrally flattened with a transverse expansion. The lateral and ventral surfaces in the symphyseal region bears a series of foramina that measure {{convert|2|to|5|mm|cm|abbr=on}} in diameter, Isolated foramina are connected internally by a complex neurovascular canal.<ref name=Stephan2014>{{cite journal|last1=Stephan|first1=L.|last2=Lawrence|first2=M. W.|last3=Perle|first3=A.|last4=Lindsay|first4=E. Z.|last5=Emily|first5=J. R.|title=Cranial anatomy of Erlikosaurus andrewsi (Dinosauria, Therizinosauria): new insights based on digital reconstruction|journal=Journal of Vertebrate Paleontology|year=2014|volume=34|issue=6|pages=1263-1291|doi=10.1080/02724634.2014.874529}}</ref>
[[File:Erlikosaurus cranial endocast.png|thumb|Reconstructed brain of ''Erlikosaurus'']]
The well preserved [[braincase]] is very much complete, only missing the sphenethmoid-mesethmoid complex, whereas the laterosphenoids and orbitosphenoids are incompletely preserved in medial view. The bones around the braincase are strongly [[Ossification|coossified]], but the [[Fibrous joint#Sutures|sutures]] between individual elements are not visible superficially, except for few exceptions.<ref name=Clark1994/> However, these internal sutures can be traced in [[Computed Tomography|CT]] scans and therefore, braincase elements could be differentiated one from other.<ref name=Stephan2014/> The restored [[brain]] of ''Erlikosaurus'' is somewhat elongated. The olfactory apparatus and the [[cerebral hemispheres]] are very notorious, with the [[olfactory tract]] being far larger than the actual brain. The cerebral hemispheres are large and broad. Interestingly, on the cerebral surface complex vascular grooves can be found, which are tipically found in [[birds]] and [[mammals]], as well as other dinosaurs. Lastly, the [[cerebellum]] is not very notorious as previous elements, it is elongated and stocky.<ref name=Lautenschlager2012/>


[[Keratinous]] [[beaks]], or rhamphothecae, are well documented among diverse groups within the [[Dinosauria]].<ref name=Stephan2014/> [[Ornithomimosaurs]] have solid evidence for it<ref name=Norell2001>{{cite journal|last1=Norell|first1=M. A.|last2=Makovicky|first2=P. J.|last3=Currie|first3=P. J.|title=The beak of ostrich dinosaurs|journal=Nature|date=2001|volume=412|pages=873–874|doi=10.1038/35091139}}</ref><ref>{{cite journal|last1=Barrett|first1=P. M.|title=The diet of ostrich dinosaurs|journal=Palaeontology|date=2005|volume=48|issue=2|pages=347–358|doi=10.1111/j.1475-4983.2005.00448.x}}</ref>, however, this is not a evidence to suggest the lack of this anatomical feature in other groups. Several characteristics are indicative of a rhamphothecae:<ref name=Stephan2014/>
As the genus is only known from very fragmentary material, it has been problematic to determine the size of ''Erlikosaurus'', especially as most of the [[vertebral column]] of the holotype is missing. The skull length is twenty-five centimetres; the humerus is thirty centimetres long. It has been estimated to attain an adult body length of six meters (twenty feet). ''Erlikosaurus'' may have been more lightly built than close relative ''[[Segnosaurus]]''.<ref name="ageofdinosaurserlikosaurus"/> Other estimates are lower: in 2010 [[Gregory S. Paul]] gave a length of 4.5 metres and a weight of half a tonne.<ref name=Paul2010>Paul, G.S., 2010, ''The Princeton Field Guide to Dinosaurs'', Princeton University Press p. 159</ref>


<blockquote>
⚫
==Discovery and naming==
''Edentulous premaxilla with a thin, tapering ventral margin, successive loss of maxillary and dentary teeth, a mandibular ventral concavity, ventral displacement of the dentary, and a rostral projection of the mandibular symphysis.''<ref name=Stephan2014/>
⚫
[[File:Erlikosaurus andrewsi.jpg|left|thumb|known elements]]
</blockquote>
The remains of ''Erlikosaurus'' were discovered in 1972 at [[Bayshin Tsav]], during a Soviet-Mongolian expedition in [[Ömnögovi Province]]. The [[type species]], ''Erlikosaurus andrewsi'', was named and described by [[Altangerel Perle]] in 1980, in an article co-authored with [[Rinchen Barsbold]], who however, is not indicated as the name-giver of this particular species. Its generic name was taken from that of the demon king [[Erlik]] from Turko-Mongolian mythology and the [[specific name (zoology)|specific name]] of the American paleontologist [[Roy Chapman Andrews]].<ref>{{cite journal |author1=Rinchen Barsbold |author2=Altangerel Perle|year=1980 |title=Segnosauria, a new infraorder of carnivorous dinosaurs |journal=Acta Palaeontologica Polonica |volume=25 |issue=2 |pages=187–195 |url=https://www.app.pan.pl/article/item/app25-187.html}}</ref> Confusingly, in 1981 Perle again named the species as if it were new, this time spelling the generic name as a Latinised "Erlicosaurus".<ref>{{cite journal |author=Altangerel Perle |year=1981 |title=Noviy segnozavrid iz verchnego mela Mongolii |journal=Trudy - Sovmestnaya Sovetsko-Mongol'skaya Paleontologicheskaya Ekspeditsiya |volume=15 |pages=50–59}}</ref> It is today generally considered that the original name, ''Erlikosaurus'', is valid.


In ''Erlikosaurus'', the presence of a keratinous beak on the maxilla and premaxilla can be infered by the presence of neurovascular foramina on the rostral and lateral surfaces. The skull of ''Erlikosaurus'' bears all the mentioned features indicative of a rhamphotheca, however it is unclear the extension of the beak.<ref name=Stephan2014/> The preserved rhamphotheca in ''[[Ornithomimus]]''<ref name=Norell2001/> evidences that the keratin sheath covered the premaxilla, and ventrally overlapped it by a few millimeters. In some extant birds, the rhamphotheca is tipically restricted to the premaxilla and maxilla, although in some cases it partially covers the nasal process in some birds.<ref>{{cite book|last1=Knutsen|first1=E. M.|title=Beak morphology in extant birds with implications on beak morphology in ornithomimids|publisher=University of Oslo|date=2007|page=44|url=https://www.duo.uio.no/bitstream/handle/10852/11777/Beakxmorphologyxinxextantxbirdsxwithximplicationsxonxbeakxmorphologyxinxornithomimosaurs_comp.pdf?sequence=1&isAllowed=y}}</ref> Apparently, in ''Erlikosaurus'' the rhamphotheca covered the nasal process of the premaxilla. To deal with this enigmatic topic, they reconstructed a conservative and extensive rhamphotheca.<ref name=Stephan2014/>
The [[holotype]], IGM 100/111, was found in layers dating from the [[Cenomanian]]-[[Santonian]]. It consists of a complete skull with lower jaws, some cervical vertebrae fragments, the left [[humerus]] and the right foot. At the time it was the only known therizinosaur (then called segnosaurs) for which a skull had been discovered.<ref name="ageofdinosaurserlikosaurus"/> This helped shed light on a puzzling and poorly known group of dinosaurs. It still represents the most completely known therizinosaurian skull.<ref name=Zanno2010>{{Cite journal|first=Lindsay E. |last=Zanno |year=2010 |title=A taxonomic and phylogenetic re-evaluation of Therizinosauria (Dinosauria: Maniraptora) |journal=Journal of Systematic Palaeontology |volume=8 |issue=4 |pages=503–543 |doi=10.1080/14772019.2010.488045 }}</ref>


===Postcrania===
Some scientists have speculated that ''Erlikosaurus'' may be the same animal as ''[[Enigmosaurus|Enigmosaurus mongoliensis]]'' named in 1983,<ref name=Paul2010/> since the latter was found in the same [[geologic formation]], and was only known from part of a hip, whereas the pelvis of ''Erlikosaurus'' is unknown. This would make ''Enigmosaurus'' a [[junior synonym]] of ''Erlikosaurus''.<ref name="ageofdinosaurserlikosaurus"/> However, since the ''Enigmosaurus'' hip did not resemble that of ''[[Segnosaurus]]'' as closely as would be expected for the ''Segnosaurus''-like ''Erlikosaurus'' remains and there is a considerable size difference, paleontologist Rinchen Barsbold disputed the alleged synonymy.<ref name="ageofdinosaurserlikosaurus">"Erlikosaurus." In: Dodson, Peter & Britt, Brooks & Carpenter, Kenneth & Forster, Catherine A. & Gillette, David D. & Norell, Mark A. & Olshevsky, George & Parrish, J. Michael & Weishampel, David B. ''The Age of Dinosaurs''. Publications International, LTD. p. 142. {{ISBN|0-7853-0443-6}}.</ref> Consequently, ''Enigmosaurus'' and ''Erlikosaurus'' are generally still considered separate genera.
Body remains of ''Erlikosaurus'' are very sparce compared to the cranial elements, consisting of a [[humerus]], a foot and some [[cervical vertebrae]]. The particular cervicals were not figured and counted, but briefly described. The cervicals are [https://commons.wikimedia.org/wiki/File:Centrum_Morphology.svg platycoelous] with low [[Vertebra#Structure|neural arches]].<ref name=Barsbold1980/> Being relatively robust, they have thick [[Articular processes|prezygapophyses]] and large parapophyses. Additional, the cervicals show some resemblance to those of ''Segnosaurus'', however, being much smaller.<ref name=PerleA1981/>

====Hindlimb====
⚫
[[File:Erlikosaurus right pes.jpg|thumb|Preserved right pes in lateral view]]
The preserved right [[Pes (anatomy)|pes]] is virtually complete, only missing the proximal end of the [[metatarsals]] II, III and IV. It is shortened in length, with robust metatarsals that bear widened articular extremities, and form a non-compact metatarsus. The metatarsal I is the shortest in comparison, expanding the laterally extended proximal [[articular surface]] of the metatarsus. All of the remaining metatarsals, are somewhat equal in size. Pedal [[Digit (anatomy)|digits]] are very peculiar in structure; the first digit is reduced in length, with all the remaining digits being nearly equal in length, however the fourth digit is very thin compared to the others. The [[phalanges]] of the three first digits are shortened, robust with comparable structure. The second and third phalanx of fourth digit are discoidal and stocky. Lastly, the [[unguals]] are recurved, exceptionally large, and strongly compressed laterally.<ref name=Barsbold1980/> Gregory S. Paul surmised that the long, slender [[claws]] of the feet were used for self-defence mechanism.<ref name=Paul2010/>

====Forelimb====
The left [[humerus]] is the only preserved remain from the pectoral region. The humerus shows an elongated [[epiphyses]] and a relatively large [[Deltoid tuberosity|deltoideal]] process.<ref name=Barsbold1980/> As pointed by Perle 1981, it is robust with an estimated maximal length of {{convert|30|cm|mm|abbr=on}}. It has a reduced shaft. The proximal end of the humeurs is greatly broad. The [[humeral head]] features an [[Joint|articular]] surface that is convex and broad, in the middle it is reduced toward the margins. A prominent [[Deltopectoral groove|deltopectoral]] crest is present with the top located 1/3 at the length of the humerus from the proximal end. The articulation [[condyles]] for the [[Radius (bone|radius]] and [[ulna]] are differentiated and divided by a shortened, furrow-like [[Fossa (anatomy)|fossa]] and overall, they are very reduced in size. The fossa for the ulnar process is moderately deep and wide. The internal roughness of the head is prominent<ref name=PerleA1981/>, as in the unrelated [[Dromaeosauridae]].<ref>{{cite journal|last1=Ostrom|first1=J. H.|title=Osteology of Deinonychus antirrhopus, an Unusual Theropod from the Lower Cretaceous of Montana|journal=Peabody Museum of Natural History Bulletin|year=1969|volume=30|pages=1–165|url=https://peabody.yale.edu/sites/default/files/documents/scientific-publications/ypmB30_1969.pdf}}</ref>


==Classification==
==Classification==
{{Main|Timeline of therizinosaur research}}
⚫
[[File:Therizinosaur endocranial elements.png|thumb|Skull of ''Erlikosaurus'' (below) and endocranial elements of other therizinosaurs]]
[[File:Erlikosaurus.jpg|thumb|left|300px|Outdated quadrupedal, prosauropod-like restoration of ''Erlikosaurus'']]
''Erlikosaurus'' was by Perle assigned to the [[Segnosauridae]], a group today known as the [[Therizinosauridae]]. This is confirmed by later [[cladistic]] analyses.<ref name=Zanno2010/>
''Erlikosaurus'' was by Perle assigned to the [[Segnosauridae]]<ref name=Barsbold1980/>, a group today known as the [[Therizinosauridae]], confirmed by later [[cladistic]] analyses.<ref name=Zanno2010/> The [[therizinosaurs]] were a strange group of [[theropods]] that ate plants instead of meat, and had a backward-facing [[pubis (bone)|pubis]], like [[ornithischians]]. Also like ornithischians, their jaws were tipped by a broad rounded bony [[beak]] useful for cropping off plants.<ref name=Dodson1993/>


The relationships of therizinosaurs were quite complicated when members were first discovered. As an example, the first known therizinosaur, ''[[Therizinosaurus]]'', was interpreted to be as a [[turtle]]-like animal that used the elongated claws to feed on seaweed.<ref>{{cite journal|last1=Maleev|first1=E. A.|title=Noviy cherepachoobrazhniy yashcher v Mongolii|trans-title=New turtle−like reptile in Mongolia|journal=Priroda|year=1954|issue=3|pages=106–108|url=https://paleoglot.org/files/Maleev%201954.pdf}}</ref> However in 1970, Rozhdestvensky proposed the idea that therizinosaurs (then known as segnosaurs) instead of being non-dinosaur creatures, they were in fact, [[theropods]].<ref>{{cite journal|last1=Rozhdestvensky|first1=A. K.|title=On the gigantic claws of mysterious Mesozoic reptiles|journal=Paleontologischeskii Zhurnal|year=1970|issue=1|pages=131–141|language=Russian}}</ref> Later, in 1980, segnosaurs were thought to be slow, [[semiaquatic]] animals, with this, Gregory S. Paul claimed that these controversial animals had no theropod characteristics and they were [[prosauropods]] with ornithischian adaptations, also, they shared evolutionary relationships.<ref>{{cite journal|last1=Paul|first1=G. S.|title=The segnosaurian dinosaurs: relics of the prosauropod-ornithischian transition?|journal=Journal of Vertebrate Paleontology|date=1984|volume=4|issue=4|pages=507–515|jstor=4523011|issn=0272-4634|doi=10.1080/02724634.1984.10012026}}</ref> However, with the description of genera ''[[Alxasaurus]]''<ref>{{cite journal|last1=Russell|first1=D. A.|last2=Dong|first2=Z.|title=The affinities of a new theropod from the Alxa Desert, Inner Mongolia, People’s Republic of China|journal=Canadian Journal of Earth Sciences|volume=30|issue=10|pages=2107–2127|year=1993|doi=10.1139/e93-183}}</ref>, ''[[Nanshiungosaurus]]''<ref>{{cite book|last1=Dong|first1=Z.|title=Dinosaurs from the Cretaceous of South China|publisher=Mesozoic and Cenozoic Red Beds of South China, Science Press|year=1979|pages=342-350|url=https://paleoglot.org/files/Dong_79.pdf|language=Chinese}}</ref>, and the redescription of the skull of ''Erlikosaurus''<ref name=Clark1994/>, more theropod evidence began to be supported. With the discovery and description of the feathered ''[[Beipiaosaurus]]'', therizinosaurs were utterly recognized as theropods, and started to be reconstructed in a accurate, bipedal posture.<ref name=Xu1999/>
The following cladogram is based on the phylogenetic analysis by Phil Senter ''et al.'', 2012.<ref name="PLoS ONE, 2012">{{Cite journal | last1 = Senter | first1 = Paul | last2 = Kirkland | first2 = James I. | last3 = Deblieux | first3 = Donald D. | editor1-last = Dodson | editor1-first = Peter | title = ''Martharaptor greenriverensis'', a New Theropod Dinosaur from the Lower Cretaceous of Utah | doi = 10.1371/journal.pone.0043911 | journal = PLoS ONE | volume = 7 | issue = 8 | pages = e43911 | year = 2012 | pmid = 22952806| pmc = 3430620}}</ref>


⚫
[[File:Therizinosaur endocranial elements.png|thumb|300px|Skull of ''Erlikosaurus'' (below) and endocranial elements of other therizinosaurs]]
⚫
{{clade| style=font-size:85%;line-height:80%
Consequently, therizinosaurs are classified as theropods in nowadays, whithin the [[Coelurosauria]]. The cladogram below is the result of the [[phylogenetic analysis]] of Therizinosauria conducted by Pu et al. [[2013 in paleontology|2013]].<ref>{{cite journal|last1=Pu|first1=H.|last2=Kobayashi|first2=Y.|last3=Lü|first3=J.|last4=Xu|first4=L.|last5=Wu|first5=Y.|last6=Chang|first6=H.|last7=Zhang|first7=J.|last8=Jia|first8=S.|title=An Unusual Basal Therizinosaur Dinosaur with an Ornithischian Dental Arrangement from Northeastern China|journal=PLoS ONE|volume=8|issue=5|pages=e63423|year=2013|doi=10.1371/journal.pone.0063423|pmid=23734177|pmc=3667168|bibcode=2013PLoSO...863423P}}</ref>
⚫
|label1=[[Therizinosauroidea]]
⚫
{{clade| style=font-size:100%;line-height:100%
|label1=[[Therizinosauria]]
|1={{clade
|1={{clade
|1=''[[Falcarius]]''
|1=''[[Falcarius]]''
|2={{clade
|2={{clade
|1=''[[Beipiaosaurus]]''
|1=''[[Jianchangosaurus]]''
⚫
|label2=[[Therizinosauroidea]]
|2={{clade
|2={{clade
|1=''[[Martharaptor]]''
|1=''[[Beipiaosaurus]]''
|2={{clade
|1=''[[Alxasaurus]]''
⚫
|label2=[[Therizinosauridae]]
|2={{clade
|2={{clade
|1=''[[Nanshiungosaurus]]''
|1=''[[Alxasaurus]]''
⚫
|label2=[[Therizinosauridae]]
|2={{clade
|2={{clade
|1=''[[Suzhousaurus]]''
|1=''[[Erliansaurus]]''
|2={{clade
|2=''[[Nanshiungosaurus]]''
|1=''[[Nothronychus]]''
|3=''[[Neimongosaurus]]''
|2={{clade
|4={{clade
|1=''[[Segnosaurus]]''
|1=''[[Segnosaurus]]''
|2={{clade
|2='''''Erlikosaurus'''''
|1=''[[Neimongosaurus]]''
|3=''[[Suzhousaurus]]''
|2=''[[Erliansaurus]]''
|4=''[[Enigmosaurus]]''
|3={{clade
|5=''[[Therizinosaurus]]''
|1='''''Erlikosaurus'''''
|6=''[[Nothronychus mckinleyi]]''
|2=''[[Therizinosaurus]]'' }} }} }} }} }} }} }} }} }} }} }}
|7=''[[Nothronychus graffami]]'' }} }} }} }} }} }} }}


==Paleobiology==
==Paleobiology==
[[File:Dentary teeth of Erlikosaurus.png|thumb|Dentary teeth]]
[[File:Dentary teeth of Erlikosaurus.png|thumb|Dentition of the [[lower jaw]] in ''Erlikosaurus'']]
[[File:Dentary teeth of Segnosaurus.png|thumb|120px|Dentition of the [[lower jaw]] in ''Segnosaurus'']]
''Erlikosaurus'' is poorly known from skeletal material, but it has recently become the focus of study in CT scans that were recently published in December 19, 2012 by Stephen Lautenschlager and Dr Emily Rayfield of Bristol University School of Earth Sciences, Professor [[Lindsay Zanno]] of the [[North Carolina Museum of Natural History]] and [[North Carolina State University]], and Lawrence Witmer, Chang Professor of Paleontology at the Ohio University Heritage College of Osteopathic Medicine. Analysis of the brain cavity revealed that ''Erlikosaurus'', and quite likely most other therizinosaurids, had well developed senses of smell, hearing, and balance, traits better associated with carnivorous theropods. The enlarged forebrain of ''Erlikosaurus'' may also have been useful in complex social behavior and predator evasion.<ref>{{cite Journal |last1=Lautenschlager |first1=Stephan |last2=Rayfield |first2=Emily J. |author3=Altangerel Perle |last4=Zanno |first4=Lindsay E. |last5=Witmer |first5=Lawrence M. |year=2012 |title=The Endocranial Anatomy of Therizinosauria and Its Implications for Sensory and Cognitive Function |journal=PLoS ONE |pages=e52289 |volume=7 |issue=12 |doi=10.1371/journal.pone.0052289|pmid=23284972 |pmc=3526574 }}</ref><ref>{{cite web |url=https://www.sciencedaily.com/releases/2012/12/121219174154.htm |title=Inside the head of a dinosaur: Research reveals new information on the evolution of dinosaur senses |author=University of Bristol |website=Science Daily |date=December 19, 2012}}</ref>
''Erlikosaurus'' is poorly known from postcranial material, but its skull became the focus of study in [[Computed Tomography|Computed Tomography (CT)]] scans that were published back in [[2012 in paleontology|2012]] by Stephen Lautenschlager and Dr Emily Rayfield of Bristol University School of Earth Sciences, Professor [[Lindsay Zanno]] of the [[North Carolina Museum of Natural History]] and [[North Carolina State University]], and Lawrence Witmer, Chang Professor of Paleontology at the Ohio University Heritage College of Osteopathic Medicine. Analysis of the brain cavity revealed that ''Erlikosaurus'', and quite likely most other therizinosaurids, had well developed senses of smell, hearing, and balance, traits better associated with [[carnivorous]] [[theropods]]. The enlarged forebrain of ''Erlikosaurus'' may also have been useful in complex [[social behavior]] and [[Ethology#Benefits and costs of group living|predator evasion]].<ref name=Lautenschlager2012/>
[[File:Erlikosaurus and Segnosaurus lower jaw.png|thumb|left|200px|Lower jaw of ''Erlikosaurus'' (bottom) and ''Segnosaurus'' (top) compared]]
⚫
The well preserved jaws of ''Erlikosaurus'' also allowed a study by the University of Bristol to determine how its feeding style and dietary preferences were linked to how wide it could open its mouth. In the study, performed by Stephen Lautenshlager et al., It was revealed that ''Erlikosaurus'' could open its mouth to a 43 degree angle at maximum. Also included in the study for comparison were the carnivorous theropods ''[[Allosaurus]]'' and ''[[Tyrannosaurus]]''. From the comparisons, it was indicated that carnivorous dinosaurs had wider jaw gapes than herbivores, much as modern carnivorous animals do today.<ref name=Lautenschlager2015>{{cite journal|first1=L.|last1=Stephan|title=Estimating cranial musculoskeletal constraints in theropod dinosaurs|year=2015|journal=Royal Society Open Science|volume=2|issue=11|doi=10.1098/rsos.150495|pmid=26716007|pmc=4680622|pages=150495}}</ref>

More findings about its exceptional skull have been made. Based on comparisons beetwen the highly specialized mandible of ''[[Segnosaurus]]'' and the simple one from ''Erlikosaurus'', these taxa were separated by [[niche partitioning]]. For instance, the mandible of ''Segnosaurus'' features very complex specializations, such as a gracile, recurved dentary, and a thickened lateral shelf. The dentition bears a triple carinae on the lower teeth, lingually folded mesial carinae appressed against triangular denticulate facets on the distal carinae, and extracarinal accessory [[Denticle (tooth feature)|denticles]]. In contrast, the dentition of ''Erlikosaurus'' seems to be more "standar", with a more simplistic morphology compared to the latter and other relatives.<ref name=Zanno2016>{{cite journal|last1=Zanno|first1=L. E.|last2=Tsogtbaatar|first2=K.|last3=Chinzorig|first3=T.|last4=Gates|first4=T. A.|title=Specializations of the mandibular anatomy and dentition of Segnosaurus galbinensis (Theropoda: Therizinosauria)|year=2016|journal=PeerJ|volume=4|page=e1885|doi=10.7717/peerj.1885}}</ref> In 2016, using [[Finite element method|Finite Element Analysis (FEA)]] and a [[Multibody system|Multibody Dynamics Analysis (MDA)]], the bite forces of ''Erlikosaurus'', ''[[Plateosaurus]]'' and ''[[Stegosaurus]]'' were tested in order to estimate dietary habits. The resulting bite force for ''Erlikosaurus'' was between 50–121 [[Newton (unit)|N]], with a skull characterised by high susceptibility to stress and deformation. This indicates a feeding behaviour that was specialised in a active use of the beak.<ref name=LautenschlagerS2016>{{cite journal|last1=Lautenschlager|first1=S.|last2=Brassey|first2=C. A.|last3=Button|first3=D. J.|last4=Barrett|first4=P. M.|title=Decoupled form and function in disparate herbivorous dinosaur clades|year=2016|journal=Nature|volume=26495|doi=10.1038/srep26495}}</ref> ''Erlikosaurus'' may have relied on postcranial musculature to compensate the low bite force and to relieve stresses on cranial structure, this is consistent with a [[herbivorous]] diet as suggested by other authors and this study.<ref>{{cite journal|last1=Zanno|first1=L. E.|last2=Gillette|first2=D. D.|last3=Albright|first3=L. B.|last4=Titus|first4=A. L.|title=A new North American therizinosaurid and the role of herbivory in ‘predatory’ dinosaur evolution|year=2009|journal=Proceedings of the Royal Society B|volume=276|doi=10.1098/rspb.2009.1029}}</ref><ref>{{cite journal|last1=Zanno|first1=L. E.|last2=Makovicky|first2=P. J.|title=Herbivorous ecomorphology and specialization patterns in theropod dinosaur evolution|year=2011|journal=Proceedings of the National Academy of Sciences|volume=108|issue=1|doi=10.1073/pnas.1011924108}}</ref><ref>{{cite journal|last1=Stephan|first1=L.|last2=Lawrence|first2=M. W.|last3=Perle|first3=A.|last4=Emily|first4=J. R.|title=Biomechanical innovations in dinosaurs|year=2013|journal=Proceedings of the National Academy of Sciences|volume=110|issue=51|doi=10.1073/pnas.1310711110}}</ref><ref name=LautenschlagerS2016/>

==Paleoecology==
[[File:Bayan Shireh Formation Fauna.png|thumb|400px|''Erlikosaurus'' compared to the known [[Dinosauria]] of the '''[[Bayan Shireh Formation]]''' (''Erlikosaurus'' in dark green, next to ''Segnosaurus'')]]
''Erlikosaurus'' was unearthed from the Bayshin Tsav locality<ref name=Barsbold1980/>, which represents part of the Upper Bayan Shireh.<ref name=Clark1994/><ref name=Tsogtbaatar2019>{{cite journal|author1=Khishigjav Tsogtbaatar |author2=David B. Weishampel |author3=David C. Evans |author4=Mahito Watabe |year=2019 |title=A new hadrosauroid (Dinosauria: Ornithopoda) from the Late Cretaceous Baynshire Formation of the Gobi Desert (Mongolia) |journal=PLoS ONE |volume=14 |issue=4 |pages=e0208480 |doi=10.1371/journal.pone.0208480 |pmid=30995236 |bibcode=2019PLoSO..1408480T }}</ref> The definitive age of the [[Bayan Shireh Formation]] has been dificult to establish, however, there are various competing hypotheses: based on comparisons with other formations, the Bayan Shireh [[fauna]] seems to correspond best with the [[Turonian]] through early [[Campanian]] stages of the Late Cretaceous, about 93 million to 80 [[million years ago]].<ref name=Jerzykiewicz1991/> Through the examination of the [[magnetostratigraphy]] of the formation conducted by Hicks et al. 1999, seems to confirm that the entire Bayan Shireh lies within the [[Cretaceous long normal|Cretaceous Long Normal]], which lasted only until the end of the [[Santonian]] stage, giving a [[Cenomanian]]-Santonian age, or, 98.5 million and 83.5 million years ago.<ref name=Hicks1999/> Dr. Thomas R. Holtz, JR. has suggested that ''Erlikosaurus'' lived between 99.6-85.8 million years ago.<ref name=Holtz2012/> However, according to Averianov and Sues in 2012, based on [[biostratigraphic]] occurences and previous datings, the Upper Bayan Shireh correlated the [[Iren Dabasu Formation]], approximately between 97 million and 83 million years ago.<ref name=Averianov2012>{{cite journal|first1=A.|last1=Averianov|first2=H.|last2=Sues|year=2012|title=Correlation of Late Cretaceous continental vertebrate assemblages in Middle and Central Asia|journal=Journal of Stratigraphy|volume=36|issue=2|pages=462-485|url=https://pdfs.semanticscholar.org/df17/104349a1f7fd4dfd76252f91817fe5f58fb6.pdf?_ga=2.179684836.1368930193.1572314200-1555398245.1565561157}}</ref>

===Enviroment and paleoflora===
[[Fluvial]], [[Lake#Paleolakes|lacustrine]] and [[caliche]]-based boundary indicates a semi-arid enviroment and climate, with the presence of large [[rivers]] and [[lakes]].<ref>{{cite journal|first1=G. G.|last1=Martinson|year=1982|title=The Upper Cretaceous mollusks of Mongolia|journal=Sovmestnaya Sovetsko– Mongolskaya Paleontolog-icheskaya Ekspeditsia|volume=17|pages=5-76}}</ref><ref>{{cite journal|first1=V. S.|last1=Samoilov|last2=Benjamini|first2=C.|year=1996|title=Geochemical features of dinosaur remains from the Gobi Desert, South Mongolia|journal=Palaios|volume=11|pages=519-531}}</ref><ref name=Averianov2012/> As interpreded by Hicks et al. 1999, during the times of the [[Bayan Shireh Formation]], large rivers drained the estern part of the [[Gobi Desert]].<ref name=Hicks1999>{{cite journal | last1 = Hicks | first1 = J. F. | last2 = Brinkman | first2 = D. L. | last3 = Nichols | first3 = D. J. | last4 = Watabe | first4 = M. | title = Paleomagnetic and palynologic analyses of Albian to Santonian strata at Bayn Shireh, Burkhant, and Khuren Dukh, eastern Gobi Desert, Mongolia | doi = 10.1006/cres.1999.0188 | journal = Cretaceous Research | volume = 20 | issue = 6 | pages = 829-850 | year = 1999 | url=https://www.academia.edu/1229640/Paleomagnetic_and_palynologic_analyses_of_Albian_to_Santonian_strata_at_Bayn_Shireh_Burkhant_and_Khuren_Dukh_eastern_Gobi_Desert_Mongolia}}</ref> The Bayan Shireh Formation is generally considered to be [[lacustrine]]<ref>{{cite journal|first1=V. S.|last1=Samoilov|last2=Benjamini|first2=C.|year=1996|title=Geochemical features of dinosaur remains from the Gobi Desert, South Mongolia|journal=Palaios|volume=11|pages=519-531}}</ref>, however, largescale cross-stratification in many of the sandstone layers at the Bayn Shireh and Burkhant localities seems to indicate a [[Meander|meandering]] [[fluvial]] system.<ref name=Hicks1999/> Many [[fossil]] [[fruits]] remains have been recovered from the Bor Guvé and Khara Khutul localities (Upper and Lower Bayan Shireh, respectively), indicating the lpresence of [[Angiosperm]] [[plants]]. The collected fruits were identified to have an ''[[Okra]]''-like appareance.<ref name=Ksepka2006>{{cite journal|first1=D. T.|last1=Ksepka|first2=M. A.|last2=Norell|year=2006|title=Erketu ellisoni, a long-necked sauropod from Bor Guvé (Dornogov Aimag, Mongolia)|journal=American Museum Novitates|issue=3508|pages=1-16|url=http://digitallibrary.amnh.org/bitstream/handle/2246/5783/N3508.pdf?sequence=1&isAllowed=y}}</ref>


===Contemporaneous paleofauna===
⚫
The well preserved jaws of ''Erlikosaurus'' also allowed a study by the University of Bristol to determine how its feeding style and dietary preferences were linked to how wide it could open its mouth. In the study, performed by Stephen Lautenshlager et al., It was revealed that ''Erlikosaurus'' could open its mouth to a 43 degree angle at maximum. Also included in the study for comparison were the carnivorous theropods ''[[Allosaurus]]'' and ''[[Tyrannosaurus]]''. From the comparisons, it was indicated that carnivorous dinosaurs had wider jaw gapes than herbivores, much as modern carnivorous animals do today.<ref>{{cite web |url=https://www.sciencedaily.com/releases/2015/11/151103213705.htm |title=The better to eat you with? How dinosaurs' jaws influenced diet |website=Science Daily |date=November 3, 2015 |author=University of Bristol}}</ref><ref>{{cite journal |title=Estimating cranial musculoskeletal constraints in theropod dinosaurs |first=Stephan |last=Lautenschlager |date=November 4, 2015 |doi=10.1098/rsos.150495 |pmid=26716007 |journal=Royal Society Open Science |volume=2 |issue=11 |pages=150495 |pmc=4680622 }}</ref>
''Erlikosaurus'' co-existed with a vast diversity of animals in the upper part of the formation, compromising dinosaur and non-dinosaur genera. Fellow [[theropods]] include the medium-sized ''[[Achillobator]]''<ref>{{cite journal|last1=Perle|first1=A.|last2=Norell|first2=M. A.|last3=Clark|first3=J.|title=A new maniraptoran Theropod - Achillobator giganticus (Dromaeosauridae) - from the Upper Cretaceous of Burkhant, Mongolia|journal=Contributions from the Geology and Mineralogy Chair, National Museum of Mongolia|date=1999|issue=101|pages=1-105|oclc=69865262|url=https://drive.google.com/open?id=1FtVZYSTmgXXBejYfYDKUIg-giwJXNy39}}</ref>, ''[[Alectrosaurus]]''<ref>{{cite journal |last1=Perle|first1=A.|title=O pervoy nakhodke Alektrozavra (Tyrannosauridae, Theropoda) iz pozdnego Mela Mongolii|trans-title=On the first discovery of Alectrosaurus (Tyrannosauridae, Theropoda) in the Late Cretaceous of Mongolia|journal=Shinzhlekh Ukhaany Akademi Geologiin Khureelen|year=1977|volume=3|issue=3|pages=104–113|language=Russian}}</ref>, ''[[Garudimimus]]''<ref>{{cite journal|last1=Barsbold|first1=R.|title=Toothless carnivorous dinosaurs of Mongolia|journal=Transactions, Joint Soviet–Mongolian Palaeontological Expedition|date=1981|volume=15|pages=28-39|url=https://pdfs.semanticscholar.org/dd82/e596b07658763756de026377a54558f3cac0.pdf}}</ref> and ''[[Segnosaurus]]''<ref name=Barsbold1980/>. The [[ankylosaurs]] ''[[Talarurus]]''<ref>{{cite journal|last1=Maleev|first1=E. A.|year=1952|title=Noviy ankilosavr is verchnego mela Mongolii|trans-title=A new ankylosaur from the Upper Cretaceous of Mongolia|journal=Doklady Akademii Nauk SSSR|volume=87|issue=2|pages=273–276|language=Russian|url=https://paleoglot.org/files/Maleev%2052tr.pdf}}</ref> and ''[[Tsagantegia]]''<ref>{{cite journal|last1=Tumanova|first1=T. A.|trans-title=A new armored dinosaur from Southeastern Gobi|title=O novom pantsirnov dinozavre iz iugo-vostochnoy Gobi|date=1993|journal=Paleontologicheskii Zhurnal|volume=27|issue=2|pages=92-98|language=Russian}}</ref>. Small [[Marginocephalia|marginocephalians]] ''[[Amtocephale]]''<ref>{{cite journal|last1=Watabe|first1=M.|last2=Tsogtbaatar|first2=K.|last3=Sullivan|first3=R. M.|year=2011|title=A new pachycephalosaurid from the Baynshire Formation (Cenomanian-late Santonian), Gobi Desert, Mongolia |url=http://www.robertmsullivanphd.com/uploads/174.Watabe_et_al__Mongolian_pachy_.pdf|journal=Fossil Record 3. New Mexico Museum of Natural History and Science, Bulletin|volume=53|pages=489–497}}</ref> and ''[[Graciliceratops]]''<ref>{{cite book|last1=Sereno|first1=P. C.|title=The Age of Dinosaurs in Russia and Mongolia|chapter=The fossil record, systematics and evolution of pachycephalosaurs and ceratopsians from Asia|date=2000|publisher=Cambridge University Press|page=489-491|url=https://d3qi0qp55mx5f5.cloudfront.net/paulsereno/i/docs/00-Marginocephalia.pdf}}</ref>. The basal [[hadrosauroid]] ''[[Gobihadros]]''<ref name=Tsogtbaatar2019/>, and the large [[sauropod]] ''[[Erketu]]''<ref name=Ksepka2006/>.<ref name=Jerzykiewicz1991>{{cite journal | last1 = Jerzykiewicz | first1 = T. | last2 = Russell | first2 = D. A. | title = Late Mesozoic stratigraphy and vertebrates of the Gobi Basin | journal = Cretaceous Research | volume = 12 | issue = 4 | pages = 345-377 | year = 1991 | issn = 0195-6671 | doi = 10.1016/0195-6671(91)90015-5}}</ref><ref>{{cite book|last1=Weishampel|first1=D. B.|last2=Dodson|first2=P.|last3=Osmolska|first3=H.|title=The Dinosauria, Second Edition|chapter=Dinosaur Distribution|date=2004|publisher=University of California Press|pages=596-597|url=https://www.researchgate.net/publication/234025996_Dinosaur_Distribution}}</ref> Other fauna includes the [[turtle]] ''[[Lindholmemys]]''<ref>{{cite journal|last1=Sukhanov|first1=V. B.|last2=Danilov|first2=I. G.|last3=Syromyatnikova|first3=E. V.|title=The Description and Phylogenetic Position of a New Nanhsiungchelyid Turtle from the Late Cretaceous of Mongolia|journal=Acta Palaeontologica Polonica|date=2008|volume=53|issue=4|pages=601-614|doi=10.4202/app.2008.0405}}</ref>, [[crocodylomorph]] ''[[Paralligator]]''<ref>{{cite journal|first1=A. H.|last1=Turner|year=2015|title=A Review of Shamosuchus and Paralligator (Crocodyliformes, Neosuchia) from the Cretaceous of Asia|journal=PLoS ONE|volume=10|issue=2|page=e0118116|doi=10.1371/journal.pone.0118116}}</ref>, unnamed [[azhdarchids]]<ref>{{cite journal|first1=M.|last1=Watabe|first2=D.|last2=Suzuki|last3=Tsogtbaatar|first3=K.|year=2009|title=The first discovery of pterosaurs from the Upper Cretaceous of Mongolia|journal=Acta Palaeontologica Polonica|volume=54|issue=2|pages=231-242|url=https://www.app.pan.pl/archive/published/app54/app54-231.pdf}}</ref> and the [[shark]] ''[[Hybodus]]''.<ref name=Averianov2012/>


==See also==
==See also==
{{Portal|Dinosaurs}}
{{Portal|Dinosaurs}}
{{Commons category|Erlikosaurus}}
* [[Timeline of therizinosaur research]]
* [[Timeline of therizinosaur research]]
* [[Altangerel Perle]]
* [[Rinchen Barsbold]]
* [[Cretaceous Mongolia]]
* [[Glossary of dinosaur anatomy]]
* [[Anatomical terms of location]]


== References ==
==References==
{{Reflist}}
{{Reflist}}


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[[Category:Therizinosaurs]]
[[Category:Therizinosaurs]]
[[Category:Taxa named by Altangerel Perle]]
[[Category:Taxa named by Altangerel Perle]]
[[Category:Taxa named by Rinchen Barsbold]]

Revision as of 06:39, 26 January 2020

Erlikosaurus
Temporal range: Late Cretaceous, 97–83 Ma
Skull and right pes of the holotype specimen MPC-D 100/111
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: Theropoda
Superfamily: †Therizinosauroidea
Family: †Therizinosauridae
Genus: †Erlikosaurus
Barsbold & Perle, 1980
Type species
†Erlikosaurus andrewsi
Barsbold & Perle, 1980

Erlikosaurus (meaning "Erlik's lizard") is a genus of therizinosaur theropod dinosaur that lived in Asia during the Late Cretaceous period. Its fossils, a skull and some post-cranial fragments, were found in the Bayan Shireh Formation of Mongolia, dating to around 97 million and 83 million years ago. Erlikosaurus represents the second therizinosaurian taxa from this Mongolian formation (alongside Enigmosaurus and Segnosaurus) with the most complete skull among other relatives of this peculiar family of dinosaurs.

Discovery and naming

Fossil localities in Mongolia. Locality of Erlikosaurus in Bayshin Tsav, at Area C
Known elements from holotype MPC-D 100/111

The holotype, MPC-D 100/111, was found in layers from the Bayshin Tsav locality on the Bayan Shireh Formation, consisting of a well preserved skull with lower jaws, some cervical vertebrae fragments and remains of the forelimb and hindlimb; these findings were made during a Soviet-Mongolian expedition in the Ömnögovi Province in 1972.[1][2] Eight years later, the genus and type species, Erlikosaurus andrewsi, was named and described (although very briefly) by paleontologists Rinchen Barsbold and Altangerel Perle in 1980, however, Barsbold was not indicated as the name-giver of this particular species. The generic name, Erlikosaurus, was taken from that of the demon king Erlik, from Turko-Mongolian mythology and the Greek σαῦρος (sauros, meaning lizard). The specific name, andrewsi, is in honour to the American paleontologist Roy Chapman Andrews, who was the leader of the American Asiatic Expeditions from 1922 to 1930.[1]

Confusingly, in 1981 Perle again named and described the species as if it were new, but this time in more detail and spelling the generic name as a Latinised "Erlicosaurus".[2] It is today widely accepted by most authors that the original name, Erlikosaurus, is valid. At the time of its discovery it was the only known therizinosaur (then called segnosaurs[3]) for which a complete skull had been discovered, this helped shed light on a puzzling and poorly known group of dinosaurs. It still represents the most completely known therizinosaurian skull.[4][5]

In 2010, Gregory S. Paul challenged the validity of this taxon, arguing that Erlikosaurus may be the same animal as Enigmosaurus mongoliensis (named in 1983[6]), since the latter was found in the same geologic formation, and was only known from pelvic remains, whereas the pelvis of Erlikosaurus is unknown; this would make Enigmosaurus a junior synonym of Erlikosaurus.[7] However, since the Enigmosaurus hip did not resemble that of Segnosaurus as closely as would be expected for the Segnosaurus-like Erlikosaurus remains, and there is a considerable size difference, paleontologist Rinchen Barsbold disputed the alleged synonymy.[8] Additional to this, Erlikosaurus and Enigmosaurus are known from upper and lower beds, respectively.[9][6][10] Consequently, Enigmosaurus and Erlikosaurus are generally still considered separate genera.[11]

Description

Partial forelimb of the basal therizinosaur Beipiaosaurus with impressions of feather-like structures, Paleozoological Museum of China
Life restoration of Erlikosaurus

The holotype is fragmentary, consisting of a exceptionally well preserved skull, a virtually complete right pes only lacking the proximal end of metatarsals II, III and IV, and an almost complete left humerus. Other remains include some fragmentary cervical vertebrae, however, the count is not specified and they were not illustrated.[1][2] Apparently, in the original description a left pes was claimed to be part of the holotype[1], however, this statement has not been mentioned again.[2][9][4][5] It is currently now know that some therizinosaurs were feathered based on the preserved skin impressions of Beipiaosaurus, so it is likely that Erlikosaurus was feathered as well.[12] As the genus is only known from very fragmentary material, it has been problematic to determine the size of Erlikosaurus, especially as most of the vertebral column of the holotype is missing. The holotype skull length is 25 cm (250 mm) long; the humerus is approximately 30 cm (300 mm) long, this indicates a very small individual. Erlikosaurus may have been more lightly built than close relative Segnosaurus with an estimated adult size of 6 m (20 ft) long.[8] Other estimates are lower: in 2010 Gregory S. Paul gave a length of 4.5 metres and a weight of 500 kg (1,100 lb).[7] Nevertheless, Thomas Holtz in 2012 estimated its length at 3.4 m (11 ft) long with a weight between 227 to 454 kg (500 to 1,001 lb).[13] Stephan et al. 2012 used theropod-specific equations to estimate the body mass of Erlikosaurus and other therizinosaurs. However, since the femur is unknown, they used bivariate regression analyses on log-transformed data; the results ended up on a femoral length of 44.33 cm (443.3 mm) and a weight of 173.7 kg (383 lb). Given the uncertainities of these estimates, they established an overall mass range between 150 to 250 kg (330 to 550 lb).[5]

Skull

File:Reconstructed beak and skull of Erlikosaurus.jpeg
Restored skull of Erlikosaurus with (A) conservative keratinous beak, and (B) extensive keratinous beak

The most studied element from Erlikosaurus is its articulated, complete skull. The snout is moderately elongated[1], with a premaxilla featuring elongated nasal processes. A fine, vertical lamina of bone is connected rostrally to the medial margin of the premaxilla, indicating that when the animal was alive, a cartilaginous internasal septum was present. Additional to this, the premaxilla features lateral and medial foramina that are connected by a complex system of vascular canals, which pervades the structure of the premaxilla and is probably associated with the sensory branches of the neurovasculature and ophthalmic nerve supporting the rhamphotheca (beak). The maxilla is triangular in shape and preserves 24 alveoli, the teeth are homodont with coarse serrations. The dentary is wedge-shaped elongated and preserves 31 alveoli. In dorsal view, it is U-shaped and dorsoventrally flattened with a transverse expansion. The lateral and ventral surfaces in the symphyseal region bears a series of foramina that measure 2 to 5 mm (0.20 to 0.50 cm) in diameter, Isolated foramina are connected internally by a complex neurovascular canal.[14]

Reconstructed brain of Erlikosaurus

The well preserved braincase is very much complete, only missing the sphenethmoid-mesethmoid complex, whereas the laterosphenoids and orbitosphenoids are incompletely preserved in medial view. The bones around the braincase are strongly coossified, but the sutures between individual elements are not visible superficially, except for few exceptions.[9] However, these internal sutures can be traced in CT scans and therefore, braincase elements could be differentiated one from other.[14] The restored brain of Erlikosaurus is somewhat elongated. The olfactory apparatus and the cerebral hemispheres are very notorious, with the olfactory tract being far larger than the actual brain. The cerebral hemispheres are large and broad. Interestingly, on the cerebral surface complex vascular grooves can be found, which are tipically found in birds and mammals, as well as other dinosaurs. Lastly, the cerebellum is not very notorious as previous elements, it is elongated and stocky.[5]

Keratinous beaks, or rhamphothecae, are well documented among diverse groups within the Dinosauria.[14] Ornithomimosaurs have solid evidence for it[15][16], however, this is not a evidence to suggest the lack of this anatomical feature in other groups. Several characteristics are indicative of a rhamphothecae:[14]

Edentulous premaxilla with a thin, tapering ventral margin, successive loss of maxillary and dentary teeth, a mandibular ventral concavity, ventral displacement of the dentary, and a rostral projection of the mandibular symphysis.[14]

In Erlikosaurus, the presence of a keratinous beak on the maxilla and premaxilla can be infered by the presence of neurovascular foramina on the rostral and lateral surfaces. The skull of Erlikosaurus bears all the mentioned features indicative of a rhamphotheca, however it is unclear the extension of the beak.[14] The preserved rhamphotheca in Ornithomimus[15] evidences that the keratin sheath covered the premaxilla, and ventrally overlapped it by a few millimeters. In some extant birds, the rhamphotheca is tipically restricted to the premaxilla and maxilla, although in some cases it partially covers the nasal process in some birds.[17] Apparently, in Erlikosaurus the rhamphotheca covered the nasal process of the premaxilla. To deal with this enigmatic topic, they reconstructed a conservative and extensive rhamphotheca.[14]

Postcrania

Body remains of Erlikosaurus are very sparce compared to the cranial elements, consisting of a humerus, a foot and some cervical vertebrae. The particular cervicals were not figured and counted, but briefly described. The cervicals are platycoelous with low neural arches.[1] Being relatively robust, they have thick prezygapophyses and large parapophyses. Additional, the cervicals show some resemblance to those of Segnosaurus, however, being much smaller.[2]

Hindlimb

File:Erlikosaurus right pes.jpg
Preserved right pes in lateral view

The preserved right pes is virtually complete, only missing the proximal end of the metatarsals II, III and IV. It is shortened in length, with robust metatarsals that bear widened articular extremities, and form a non-compact metatarsus. The metatarsal I is the shortest in comparison, expanding the laterally extended proximal articular surface of the metatarsus. All of the remaining metatarsals, are somewhat equal in size. Pedal digits are very peculiar in structure; the first digit is reduced in length, with all the remaining digits being nearly equal in length, however the fourth digit is very thin compared to the others. The phalanges of the three first digits are shortened, robust with comparable structure. The second and third phalanx of fourth digit are discoidal and stocky. Lastly, the unguals are recurved, exceptionally large, and strongly compressed laterally.[1] Gregory S. Paul surmised that the long, slender claws of the feet were used for self-defence mechanism.[7]

Forelimb

The left humerus is the only preserved remain from the pectoral region. The humerus shows an elongated epiphyses and a relatively large deltoideal process.[1] As pointed by Perle 1981, it is robust with an estimated maximal length of 30 cm (300 mm). It has a reduced shaft. The proximal end of the humeurs is greatly broad. The humeral head features an articular surface that is convex and broad, in the middle it is reduced toward the margins. A prominent deltopectoral crest is present with the top located 1/3 at the length of the humerus from the proximal end. The articulation condyles for the radius and ulna are differentiated and divided by a shortened, furrow-like fossa and overall, they are very reduced in size. The fossa for the ulnar process is moderately deep and wide. The internal roughness of the head is prominent[2], as in the unrelated Dromaeosauridae.[18]

Classification

Main article: Timeline of therizinosaur research
Outdated quadrupedal, prosauropod-like restoration of Erlikosaurus

Erlikosaurus was by Perle assigned to the Segnosauridae[1], a group today known as the Therizinosauridae, confirmed by later cladistic analyses.[4] The therizinosaurs were a strange group of theropods that ate plants instead of meat, and had a backward-facing pubis, like ornithischians. Also like ornithischians, their jaws were tipped by a broad rounded bony beak useful for cropping off plants.[8]

The relationships of therizinosaurs were quite complicated when members were first discovered. As an example, the first known therizinosaur, Therizinosaurus, was interpreted to be as a turtle-like animal that used the elongated claws to feed on seaweed.[19] However in 1970, Rozhdestvensky proposed the idea that therizinosaurs (then known as segnosaurs) instead of being non-dinosaur creatures, they were in fact, theropods.[20] Later, in 1980, segnosaurs were thought to be slow, semiaquatic animals, with this, Gregory S. Paul claimed that these controversial animals had no theropod characteristics and they were prosauropods with ornithischian adaptations, also, they shared evolutionary relationships.[21] However, with the description of genera Alxasaurus[22], Nanshiungosaurus[23], and the redescription of the skull of Erlikosaurus[9], more theropod evidence began to be supported. With the discovery and description of the feathered Beipiaosaurus, therizinosaurs were utterly recognized as theropods, and started to be reconstructed in a accurate, bipedal posture.[12]

Skull of Erlikosaurus (below) and endocranial elements of other therizinosaurs

Consequently, therizinosaurs are classified as theropods in nowadays, whithin the Coelurosauria. The cladogram below is the result of the phylogenetic analysis of Therizinosauria conducted by Pu et al. 2013.[24]

Therizinosauria

Paleobiology

Dentition of the lower jaw in Erlikosaurus
Dentition of the lower jaw in Segnosaurus

Erlikosaurus is poorly known from postcranial material, but its skull became the focus of study in Computed Tomography (CT) scans that were published back in 2012 by Stephen Lautenschlager and Dr Emily Rayfield of Bristol University School of Earth Sciences, Professor Lindsay Zanno of the North Carolina Museum of Natural History and North Carolina State University, and Lawrence Witmer, Chang Professor of Paleontology at the Ohio University Heritage College of Osteopathic Medicine. Analysis of the brain cavity revealed that Erlikosaurus, and quite likely most other therizinosaurids, had well developed senses of smell, hearing, and balance, traits better associated with carnivorous theropods. The enlarged forebrain of Erlikosaurus may also have been useful in complex social behavior and predator evasion.[5]

Lower jaw of Erlikosaurus (bottom) and Segnosaurus (top) compared

The well preserved jaws of Erlikosaurus also allowed a study by the University of Bristol to determine how its feeding style and dietary preferences were linked to how wide it could open its mouth. In the study, performed by Stephen Lautenshlager et al., It was revealed that Erlikosaurus could open its mouth to a 43 degree angle at maximum. Also included in the study for comparison were the carnivorous theropods Allosaurus and Tyrannosaurus. From the comparisons, it was indicated that carnivorous dinosaurs had wider jaw gapes than herbivores, much as modern carnivorous animals do today.[25]

More findings about its exceptional skull have been made. Based on comparisons beetwen the highly specialized mandible of Segnosaurus and the simple one from Erlikosaurus, these taxa were separated by niche partitioning. For instance, the mandible of Segnosaurus features very complex specializations, such as a gracile, recurved dentary, and a thickened lateral shelf. The dentition bears a triple carinae on the lower teeth, lingually folded mesial carinae appressed against triangular denticulate facets on the distal carinae, and extracarinal accessory denticles. In contrast, the dentition of Erlikosaurus seems to be more "standar", with a more simplistic morphology compared to the latter and other relatives.[26] In 2016, using Finite Element Analysis (FEA) and a Multibody Dynamics Analysis (MDA), the bite forces of Erlikosaurus, Plateosaurus and Stegosaurus were tested in order to estimate dietary habits. The resulting bite force for Erlikosaurus was between 50–121 N, with a skull characterised by high susceptibility to stress and deformation. This indicates a feeding behaviour that was specialised in a active use of the beak.[27] Erlikosaurus may have relied on postcranial musculature to compensate the low bite force and to relieve stresses on cranial structure, this is consistent with a herbivorous diet as suggested by other authors and this study.[28][29][30][27]

Paleoecology

Erlikosaurus compared to the known Dinosauria of the Bayan Shireh Formation (Erlikosaurus in dark green, next to Segnosaurus)

Erlikosaurus was unearthed from the Bayshin Tsav locality[1], which represents part of the Upper Bayan Shireh.[9][10] The definitive age of the Bayan Shireh Formation has been dificult to establish, however, there are various competing hypotheses: based on comparisons with other formations, the Bayan Shireh fauna seems to correspond best with the Turonian through early Campanian stages of the Late Cretaceous, about 93 million to 80 million years ago.[31] Through the examination of the magnetostratigraphy of the formation conducted by Hicks et al. 1999, seems to confirm that the entire Bayan Shireh lies within the Cretaceous Long Normal, which lasted only until the end of the Santonian stage, giving a Cenomanian-Santonian age, or, 98.5 million and 83.5 million years ago.[32] Dr. Thomas R. Holtz, JR. has suggested that Erlikosaurus lived between 99.6-85.8 million years ago.[13] However, according to Averianov and Sues in 2012, based on biostratigraphic occurences and previous datings, the Upper Bayan Shireh correlated the Iren Dabasu Formation, approximately between 97 million and 83 million years ago.[33]

Enviroment and paleoflora

Fluvial, lacustrine and caliche-based boundary indicates a semi-arid enviroment and climate, with the presence of large rivers and lakes.[34][35][33] As interpreded by Hicks et al. 1999, during the times of the Bayan Shireh Formation, large rivers drained the estern part of the Gobi Desert.[32] The Bayan Shireh Formation is generally considered to be lacustrine[36], however, largescale cross-stratification in many of the sandstone layers at the Bayn Shireh and Burkhant localities seems to indicate a meandering fluvial system.[32] Many fossil fruits remains have been recovered from the Bor Guvé and Khara Khutul localities (Upper and Lower Bayan Shireh, respectively), indicating the lpresence of Angiosperm plants. The collected fruits were identified to have an Okra-like appareance.[37]

Contemporaneous paleofauna

Erlikosaurus co-existed with a vast diversity of animals in the upper part of the formation, compromising dinosaur and non-dinosaur genera. Fellow theropods include the medium-sized Achillobator[38], Alectrosaurus[39], Garudimimus[40] and Segnosaurus[1]. The ankylosaurs Talarurus[41] and Tsagantegia[42]. Small marginocephalians Amtocephale[43] and Graciliceratops[44]. The basal hadrosauroid Gobihadros[10], and the large sauropod Erketu[37].[31][45] Other fauna includes the turtle Lindholmemys[46], crocodylomorph Paralligator[47], unnamed azhdarchids[48] and the shark Hybodus.[33]

See also

Wikimedia Commons has media related to Erlikosaurus.

References

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