Editing Protoceratops (section)

==Paleoenvironment==
===Bayan Mandahu Formation===
[[File:Protoceratops in Bayan Mandahu.png|thumb|left|Restoration of a ''P. hellenikorhinus'' pair in the Bayan Mandahu Formation]]
Based on general similarities between the vertebrate fauna and sediments of Bayan Mandahu and the Djadokhta Formation, the [[Bayan Mandahu Formation]] is considered to be [[Late Cretaceous]] in age, roughly [[Campanian]]. The dominant [[lithology]] is reddish-brown, poorly cemented, fine grained [[sandstone]] with some [[Conglomerate (geology)|conglomerate]], and [[caliche]]. Other facies include [[alluvial]] (stream-deposited) and [[Aeolian processes|eolian]] (wind-deposited) [[sediment]]s. It is likely that sediments at Bayan Mandahu were deposited by short-lived rivers and lakes on an alluvial plain (flat land consisting of sediments deposited by highland rivers) with a combination of [[dune]] field paleoenvironments, under a [[semi-arid climate]]. The formation is known for its vertebrate fossils in life-like poses, most of which are preserved in unstructured sandstone, indicating a catastrophic rapid burial.<ref name=Jerzykiewiczz1993/><ref>{{cite journal|last1=Eberth|first1=D. A.|date=1993|title=Depositional environments and facies transitions of dinosaur-bearing Upper Cretaceous redbeds at Bayan Mandahu (Inner Mongolia, People's Republic of China)|journal=Canadian Journal of Earth Sciences|volume=30|number=10|pages=2196–2213|doi=10.1139/e93-191|bibcode=1993CaJES..30.2196E }}</ref>

The [[Fauna|paleofauna]] of Bayan Mandahu is very similar in composition to the nearby Djadokhta Formation, with both formations sharing several of the same genera, but differing in the exact species. In this formation, ''P. hellenikorhinus'' is the representative species, and it shared its paleoenvironment with numerous dinosaurs such as [[dromaeosaurid]]s ''[[Linheraptor]]'' and ''[[Velociraptor]] osmolskae'';<ref>{{cite journal|last1=Godefroit|first1=P.|last2=Currie|first2=P. J.|last3=Li|first3=H.|last4=Shang|first4=C. Y.|last5=Dong|first5=Z.-M.|date=2008|title=A new species of Velociraptor (Dinosauria: Dromaeosauridae) from the Upper Cretaceous of northern China|journal=Journal of Vertebrate Paleontology|volume=28|issue=2|pages=432–438|doi=10.1671/0272-4634(2008)28[432:ANSOVD]2.0.CO;2|jstor=20490961|s2cid=129414074 }}</ref><ref>{{cite journal|last1=Xing|first1=X.|last2=Choinere|first2=J. N.|last3=Pittman|first3=M.|last4=Tan|first4=Q. W.|last5=Xiao|first5=D.|last6=Li|first6=Z. Q.|last7=Tan|first7=L.|last8=Clark|first8=J. M.|last9=Norell|first9=M. A.|last10=Hone|first10=D. W. E|last11=Sullivan|first11=C.|date= 2010|title=A new dromaeosaurid (Dinosauria: Theropoda) from the Upper Cretaceous Wulansuhai Formation of Inner Mongolia, China|journal=Zootaxa|volume=2403|number=1|pages=1–9|doi=10.11646/zootaxa.2403.1.1|doi-access=free|url=http://www.mapress.com/zootaxa/2010/f/zt02403p009.pdf}}</ref> [[oviraptorids]] ''[[Machairasaurus]]'' and ''[[Wulatelong]]'';<ref name=Longrich2010/><ref>{{cite journal|last1=Xing|first1=X.|last2=Qing-Wei|first2=T.|last3=Shuo|first3=W.|last4=Sullivan|first4=C.|last5=Hone|first5=D. W. E.|last6=Feng-Lu|first6=H.|last7=Qing-Yu|first7=M.|last8=Lin|first8=T.|last9=Dong|first9=T.|date=2013|title=A new oviraptorid from the Upper Cretaceous of Nei Mongol,China, and its stratigraphic implications|journal=Vertebrata PalAsiatica|volume=51|issue=2|pages=85–101|url=http://www.ivpp.cas.cn/cbw/gjzdwxb/xbwzxz/201305/P020130507385115746165.pdf}}</ref> and [[troodontid]]s ''[[Linhevenator]]'', ''[[Papiliovenator]]'', and ''[[Philovenator]]''.<ref>{{cite journal|last1=Pei|first1=R.|last2=Qin|first2=Yuying|last3=Wen|first3=Aishu|last4=Zhao|first4=Q.|last5=Wang|first5=Z.|last6=Liu|first6=Z.|last7=Guo|first7=W.|last8=Liu|first8=P.|last9=Ye|first9=W.|last10=Wang|first10=L.|last11=Yin|first11=Z.|last12=Dai|first12=R.|last13=Xu|first13=X.|date=2022|title=A new troodontid from the Upper Cretaceous Gobi Basin of inner Mongolia, China|journal=Cretaceous Research|volume=130|number=105052|page=105052 |doi=10.1016/j.cretres.2021.105052|bibcode=2022CrRes.13005052P |s2cid=244186762 }}</ref> Other dinosaur members include the [[alvarezsaurid]] ''[[Linhenykus]]'';<ref>{{cite journal|last1=Xing|first1=X.|last2=Sullivan|first2=Corwin|last3=Pittman|first3=M.|last4=Choiniere|first4=J. N.|last5=Hone|first5=D. W. E.|last6=Upchurch|first6=P.|last7=Tan|first7=Q.|last8=Xiao|first8=Dong|last9=Lin|first9=Tan|last10=Han|first10=F.|date=2011 |title=A monodactyl nonavian dinosaur and the complex evolution of the alvarezsauroid hand|journal=Proceedings of the National Academy of Sciences of the United States of America|volume=108|number=6|pages=2338–2342|bibcode=2011PNAS..108.2338X|doi=10.1073/pnas.1011052108|doi-access=free|pmc=3038769|pmid=21262806}}</ref> [[ankylosaurid]] ''[[Pinacosaurus]] mephistocephalus'';<ref>{{cite journal|last1=Godefroit|first1=P.|last2=Pereda-Suberbiola|first2=X.|last3=Li|first3=H.|last4=Dong|first4=Z. M.|date=1999|title=A new species of the ankylosaurid dinosaur Pinacosaurus from the Late Cretaceous of Inner Mongolia (P.R. China)|journal=Bulletin de l'Institut Royal des Sciences Naturelles de Belgique, Sciences de la Terre|volume=69|issue=supp. B|pages=17–36|url=http://biblio.naturalsciences.be/rbins-publications/bulletin-of-the-royal-belgian-institute-of-natural-sciences-earth-sciences/69-sup-b-1999/bulletin69supb-article2.pdf}}</ref><ref name=CurrieP2011>{{cite journal|last1=Currie|first1=P. J.|last2=Badamgarav|first2=D.|last3=Koppelhus|first3=E. B.|last4=Sissons|first4=R.|last5=Vickaryous|first5=M. K.|date=2011|title=Hands, feet and behaviour in Pinacosaurus (Dinosauria: Ankylosauridae)|journal=Acta Palaeontologica Polonica|volume=56|issue=3|pages=489–504|doi=10.4202/app.2010.0055|s2cid=129291148|doi-access=free|url=http://www.app.pan.pl/archive/published/app56/app20100055.pdf}}</ref> and closely related [[protoceratopsid]] ''[[Bagaceratops]]''.<ref name=Czepiński19/> Additional fauna from this unit comprises [[nanhsiungchelyid]]s turtles,<ref>{{cite journal|last1=Brinkman|first1=D. B.|last2=Tong|first2=H.-Y.|last3=Li|first3=H.|last4=Sun|first4=Y.|last5=Zhang|first5=J.-S.|last6=Godefroit|first6=P.|last7=Zhang|first7=Z.-M.|date=2015|title=New exceptionally well-preserved specimens of "Zangerlia" neimongolensis from Bayan Mandahu, Inner Mongolia, and their taxonomic significance|journal=Comptes Rendus Palevol|volume=14|issue=6–7|pages=577–587|doi=10.1016/j.crpv.2014.12.005|bibcode=2015CRPal..14..577B |doi-access=free}}</ref> and a variety of [[squamates]] and [[mammal]]s.<ref>{{cite journal|last1=Gao|first1=K.|last2=Hou|first2=L.|date=1996|title=Systematics and taxonomic diversity of squamates from the Upper Cretaceous Djadochta Formation, Bayan Mandahu, Gobi Desert, People's Republic of China|journal=Canadian Journal of Earth Sciences|volume=33|issue=4|pages=578–598|bibcode=1996CaJES..33..578G|doi=10.1139/e96-043}}</ref><ref>{{cite journal|last1=Wible|first1=J. R.|last2=Shelley|first2=S. L.|last3=Bi|first3=S.|date=2019|title=New Genus and Species of Djadochtatheriid Multituberculate (Allotheria, Mammalia) from the Upper Cretaceous Bayan Mandahu Formation of Inner Mongolia|journal=Annals of Carnegie Museum|volume=85|issue=4|pages=285–327|doi=10.2992/007.085.0401|bibcode=2019AnCM...85..285W |s2cid=210840006|url=https://www.researchgate.net/publication/338202993}}</ref>

===Djadokhta Formation===
[[File:Protoceratops in Djadokhta.png|thumb|Restoration of a ''P. andrewsi'' group in the Djadokhta Formation]]
''Protoceratops'' is known from most localities of the [[Djadokhta Formation]] in Mongolia, which dates back to the Late Cretaceous about 71 million to 75&nbsp;million years ago, being deposited during a rapid sequence of polarity changes in the late part of the Campanian stage.<ref name=Dashzeveg2005>{{cite journal|last1=Dashzeveg|first1=D.|last2=Dingus|first2=L.|last3=Loope|first3=D. B.|last4=Swisher III|first4=C. C.|last5=Dulam|first5=T.|last6=Sweeney|first6=M. R.|date=2005|title=New Stratigraphic Subdivision, Depositional Environment, and Age Estimate for the Upper Cretaceous Djadokhta Formation, Southern Ulan Nur Basin, Mongolia|journal=American Museum Novitates|number=3498|pages=1–31|doi=10.1206/0003-0082(2005)498[0001:NSSDEA]2.0.CO;2|hdl=2246/5667|s2cid=55836458 |hdl-access=free|url=http://digitallibrary.amnh.org/bitstream/handle/2246/5667/N3498.pdf?sequence=1&isAllowed=y}}</ref> Dominant sediments at Djadokhta include dominant reddish-orange and pale orange to light gray, medium to fine-grained [[sand]]s and sandstones, caliche, and sparse [[fluvial]] (river-deposited) processes. Based on these components, the paleoenvironments of the Djadokhta Formation are interpreted as having a hot, semiarid climate with large dune fields/sand dunes and several short-lived [[water bodies]], similar to the modern [[Gobi Desert]]. It is estimated that at the end of the Campanian age and into the [[Maastrichtian]] the climate would shift to the more [[Mesic habitat|mesic]] (humid/wet) conditions seen in the [[Nemegt Formation]].<ref>{{cite book|last1=Jerzykiewicz|first1=T.|year=1997|chapter=Djadokhta Formation|editor-last1=Currie|editor-first1=P. J.|editor-last2=Padian|editor-first2=K.|title=Encyclopedia of Dinosaurs|url-access=limited|publisher=Academic Press|location=San Diego|pages=[https://archive.org/details/encyclopediadino00curr_075/page/n218 188]−191|isbn=978-0-12-226810-6|url=https://archive.org/details/encyclopediadino00curr_075}}</ref><ref name=Dingus2008>{{cite journal|last1=Dingus|first1=L.|last2=Loope|first2=D. B.|last3=Dashzeveg|first3=D.|last4=Swisher III|first4=C. C.|last5=Minjin|first5=C.|last6=Novacek|first6=M. J.|last7=Norell|first7=M. A.|date=2008|title=The Geology of Ukhaa Tolgod (Djadokhta Formation, Upper Cretaceous, Nemegt Basin, Mongolia)|journal=American Museum Novitates|number=3616|pages=1–40|doi=10.1206/442.1|hdl=2246/5916|s2cid=129735494 |hdl-access=free|url=https://core.ac.uk/download/pdf/189860633.pdf}}{{Dead link|date=June 2022 |bot=InternetArchiveBot |fix-attempted=yes }}</ref><ref name=Chinzoorig2017>{{cite journal|last1=Chinzorig|first1=T.|last2=Kobayashi|first2=Y.|last3=Tsogtbaatar|first3=K.|last4=Currie|first4=P. J.|last5=Watabe|first5=M.|last6=Barsbold|first6=R.|date=2017|title=First Ornithomimid (Theropoda, Ornithomimosauria) from the Upper Cretaceous Djadokhta Formation of Tögrögiin Shiree, Mongolia|journal=Scientific Reports|volume=7|issue=5835|page=5835 |bibcode=2017NatSR...7.5835C|doi=10.1038/s41598-017-05272-6|doi-access=free|pmc=5517598|pmid=28724887}}</ref>

The Djadokhta Formation is separated into a lower Bayn Dzak Member and upper Turgrugyin Member. ''Protoceratops'' is largely known from both members, having ''P. andrewsi'' as a dominant and representative species in the overall formation.<ref name=Dashzeveg2005/><ref name=Dingus2008/> The Bayn Dzak member (mostly the Bayn Dzak locality) has yielded the dromaeosaurids ''[[Halszkaraptor]]'' and ''Velociraptor mongoliensis'';<ref name=Norel1999>{{cite journal|last1=Norell|first1=M. A.|last2=Makovicky|first2=P. J.|date=1999|title=Important Features of the Dromaeosaurid Skeleton II: Information from Newly Collected Specimens of Velociraptor mongoliensis|journal=American Museum Novitates|number=3282|pages=1–45|hdl=2246/3025|hdl-access=free|oclc=802169086}}</ref><ref>{{cite journal|last1=Cau|first1=A.|last2=Beyrand|first2=V.|last3=Voeten|first3=D. F. A. E.|last4=Fernandez|first4=V.|last5=Tafforeau|first5=P.|last6=Stein|first6=K.|last7=Barsbold|first7=R.|last8=Tsogtbaatar|first8=K.|last9=Currie|first9=P. J.|last10=Godefroit|first10=P.|date=2017|title=Synchrotron scanning reveals amphibious ecomorphology in a new clade of bird-like dinosaurs|journal=Nature|volume=552|issue=7685|pages=395–399|bibcode=2017Natur.552..395C|doi=10.1038/nature24679|pmid=29211712|s2cid=4471941 |url=https://www.researchgate.net/publication/321609878}}</ref> oviraptorid ''[[Oviraptor]]'';<ref name=Osborn1924/> ankylosaurid ''Pinacosaurus grangeri'';<ref name=CurrieP2011/> and troodontid ''[[Saurornithoides]]''.<ref>{{cite journal|last1=Norell|first1=M. A.|last2=Makovicky|first2=P. J.|last3=Bever|first3=G. S.|last4=Balanoff|first4=A. M.|last5=Clark|first5=J. M.|last6=Barsbold|first6=R.|last7=Rowe|first7=T.|date=2009|title=A review of the Mongolian Cretaceous dinosaur Saurornithoides (Troodontidae, Theropoda)|journal=American Museum Novitates|number=3654|pages=1–63|doi=10.1206/648.1|hdl=2246/5973|hdl-access=free|url=https://www.biodiversitylibrary.org/itempdf/280747}}</ref> Ukhaa Tolgod, a highly fossiliferous locality is also included in the Bayn Dzak member.<ref name=Dingus2008/> and its dinosaur paleofauna is composed of alvarezsaurids ''[[Kol (dinosaur)|Kol]]'' and ''[[Shuvuuia]]'';<ref>{{cite journal|last1=Suzuki|first1=S.|last2=Chiappe|first2=L. M.|last3=Dyke|first3=G. J.|last4=Watabe|first4=M.|last5=Barsbold|first5=R.|last6=Tsogtbaatar|first6=K.|date=2002|title=A New Specimen of Shuvuuia deserti Chiappe et al., 1998, from the Mongolian Late Cretaceous with a Discussion of the Relationships of Alvarezsaurids to Other Theropod Dinosaurs|journal=Contributions in Science|volume=494|pages=1–18|doi=10.5962/p.226791|s2cid=135344028 |doi-access=free}}</ref><ref>{{cite journal|first1=A. H.|last1=Turner|first2=S. J.|last2=Nesbitt|first3=M. A.|last3=Norell|date=2009|title=A Large Alvarezsaurid from the Late Cretaceous of Mongolia|journal=American Museum Novitates|number=3648|pages=1–14|doi=10.1206/639.1|hdl=2246/5967|hdl-access=free|s2cid=59459861|url=https://digitallibrary.amnh.org/bitstream/handle/2246/5967/N3648.pdf?sequence=1&isAllowed=y}}</ref> ankylosaurid ''[[Minotaurasaurus]]'';<ref>{{cite journal|last1=Alicea|first1=J.|last2=Loewen|first2=M.|date=2013|title=New Minotaurasaurus material from the Djodokta Formation establishes new taxonomic and stratigraphic criteria for the taxon|journal=Journal of Vertebrate Paleontology|volume=Program and Abstracts|page=76|url=http://vertpaleo.org/Annual-Meeting/Future-Past-Meetings/MeetingPdfs/SVP-2013-merged-book-10-15-2013.aspx}}</ref> birds ''[[Apsaravis]]'' and ''[[Gobipteryx]]'';<ref>{{cite journal|last1=Chiappe|first1=L. M.|last2=Norell|first2=M. A.|last3=Clark|first3=J.|date=2001|title=A New Skull of Gobipteryx minuta (Aves: Enantiornithes) from the Cretaceous of the Gobi Desert|journal=American Museum Novitates|number=3346|pages=1–15|doi=10.1206/0003-0082(2001)346<0001:ANSOGM>2.0.CO;2|hdl=2246/2899|s2cid=51857603 |hdl-access=free|url=https://archive.org/download/newskullgobipte3346chia/newskullgobipte3346chia.pdf}}.</ref><ref>{{cite journal|last1=Clarke|first1=J. A.|last2=Norell|first2=M. A.|date=2002|title=The Morphology and Phylogenetic Position of Apsaravis ukhaana from the Late Cretaceous of Mongolia|journal=American Museum Novitates|number=3387|pages=1–46|doi=10.1206/0003-0082(2002)387<0001:TMAPPO>2.0.CO;2|hdl=2246/2876|s2cid=52971055 |hdl-access=free|url=https://digitallibrary.amnh.org/bitstream/handle/2246/2876//v2/dspace/ingest/pdfSource/nov/N3387.pdf?sequence=1&isAllowed=y}}</ref> dromaeosaurid ''[[Tsaagan]]'';<ref>{{cite journal|last1=Norell|first1=M. A.|last2=Clark|first2=J. M.|last3=Turner|first3=A. H.|last4=Makovicky|first4=P. J.|last5=Barsbold|first5=R.|last6=Rowe|first6=T.|date=2006|title=A New Dromaeosaurid Theropod from Ukhaa Tolgod (Ömnögov, Mongolia)|journal=American Museum Novitates|number=3545|pages=1–51|doi=10.1206/0003-0082(2006)3545[1:ANDTFU]2.0.CO;2|hdl=2246/5823|hdl-access=free|url=https://www.researchgate.net/publication/232678611}}</ref> oviraptorids ''[[Citipati]]'' and ''[[Khaan]]'';<ref>{{cite journal|last1=Clark|first1=J. M.|last2=Norell|first2=M. A.|last3=Barsbold|first3=R.|date=2001|title=Two new oviraptorids (Theropoda: Oviraptorosauria) from the Late Cretaceous Djadokta Formation, Ukhaa Tolgod|journal=Journal of Vertebrate Paleontology|volume=21|issue=2|pages=209–213|doi=10.1671/0272-4634(2001)021[0209:TNOTOU]2.0.CO;2|jstor=20061948|s2cid=86076568 |url=https://www.researchgate.net/publication/232685671}}</ref> troodontids ''[[Almas ukhaa|Almas]]'' and ''[[Byronosaurus]]'';<ref>{{cite journal|last1=Makovicky|first1=P. J.|last2=Norell|first2=M. A.|last3=Clark|first3=J. M.|last4=Rowe|first4=T. E.|date=2003|title=Osteology and Relationships of Byronosaurus jaffei (Theropoda: Troodontidae)|journal=American Museum Novitates|number=3402|pages=1–32|doi=10.1206/0003-0082(2003)402<0001:oarobj>2.0.co;2|hdl=2246/2828|s2cid=51824767 |hdl-access=free|url=https://digitallibrary.amnh.org/bitstream/handle/2246/2828//v2/dspace/ingest/pdfSource/nov/N3402.pdf?sequence=1&isAllowed=y}}</ref><ref>{{cite journal|last1=Pei|first1=R.|last2=Norell|first2=M. A.|last3=Barta|first3=D. E|last4=Bever|first4=G. S.|last5=Pittman|first5=M.|last6=Xu|first6=X.|date=2017|title=Osteology of a New Late Cretaceous Troodontid Specimen from Ukhaa Tolgod, Ömnögovi Aimag, Mongolia|journal=American Museum Novitates|number=3889|pages=1–47|doi=10.1206/3889.1|hdl=2246/6818|hdl-access=free|s2cid=90883541|url=https://ia903007.us.archive.org/27/items/osteologynewlat00peir/osteologynewlat00peir.pdf}}</ref> and a new, unnamed protoceratopsid closely related to ''Protoceratops''.<ref>{{cite journal|last1=Prieto-Márquez|first1=A.|last2=Garcia-Porta|first2=J.|last3=Joshi|first3=S. H.|last4=Norell|first4=M. A.|last5=Makovicky|first5=P. J.|date=2020|title=Modularity and heterochrony in the evolution of the ceratopsian dinosaur frill|journal=Ecology and Evolution|volume=10|issue=13|pages=6288–6309|doi=10.1002/ece3.6361|doi-access=free|pmc=7381594|pmid=32724514|bibcode=2020EcoEv..10.6288P }}</ref> In the Turgrugyin Member (mainly Tugriken Shireh locality), ''P. andrewsi'' shared its paleoenvironment with the bird ''[[Elsornis]]'';<ref>{{cite journal|last1=Chiappe|first1=L. M.|last2=Suzuki|first2=S.|last3=Dyke|first3=G. J.|last4=Watabe|first4=M.|last5=Tsogtbaatar|first5=K.|last6=Barsbold|first6=R.|date=2007|title=A new Enantiornithine bird from the Late Cretaceous of the Gobi desert|journal=Journal of Systematic Palaeontology|volume=5|issue=2|pages=193–208|doi=10.1017/S1477201906001969|bibcode=2007JSPal...5..193C |s2cid=85391743}}</ref> dromaeosaurids ''[[Mahakala omnogovae|Mahakala]]'' and ''Velociraptor mongoliensis'';<ref name=Norel1999/><ref>{{cite journal|last1=Turner|first1=A. H.|last2=Pol|first2=D.|last3=Clarke|first3=J. A.|last4=Erickson|first4=G. M.|last5=Norell|first5=M. A.|date=2007|title=A Basal Dromaeosaurid and Size Evolution Preceding Avian Flight|journal=Science|volume=317|issue=5843|pages=1378–1381|bibcode=2007Sci...317.1378T|doi=10.1126/science.1144066|doi-access=free|pmid=17823350}}</ref> and [[ornithomimid]] ''[[Aepyornithomimus]]''.<ref name=Chinzoorig2017/> ''P. andrewsi'' is also abundant at Udyn Sayr,<ref name=Handa2012/><ref name=Czepiński2020/> where ''[[Avimimus]]'' and ''[[Udanoceratops]]'' have been recovered.<ref>{{cite journal|last1=Kurzanov|first1=S. M.|date=1992|title=A giant protoceratopsid from the Upper Cretaceous of Mongolia|journal=Paleontological Journal|pages=81–93|language=ru}}</ref><ref>{{cite journal|last1=Watabe|first1=M.|last2=Suzuki|first2=S.|last3=Tsogtbaatar|first3=K.|date=2006|title=Geological and geographical distribution of bird-like theropod, Avimimus in Mongolia|journal =Journal of Vertebrate Paleontology|volume=26|issue=supp. 003|pages=136A−137A|doi=10.1080/02724634.2006.10010069|s2cid=220413406}}</ref>

The relatively low dinosaur paleodiversity, small body size of most dinosaurs, and [[arid]] settings of the Djadokhta Formation compared to those of the Nemegt Formation, suggest that ''Protoceratops'' and contemporaneous biota lived in a [[Stress (biology)|stressed]] paleoenvironment (physical factors that generate adverse impacts on the ecosystem).<ref name=Longriich20110/> In addition, the high occurrence of protoceratopsid fossils in arid-deposited formations indicates that these ceratopsians preferred warm environments.<ref name=Longrich2010/><ref name=Longriich20110/> Although ''P. andrewsi'' was the predominant protoceratopsid on this formation, tentative remains of ''P. hellenikorhinus'' have been reported from the Udyn Sayr and Bor Tolgoi localities, suggesting that both species co-existed. Whereas ''P. andrewsi'' is found in aeolian sediments (Bayn Dzak or Tugriken Shireh), ''P. hellenikorhinus'' is found in the aeolian-fluvial sediments. As the latter type of sediments is also found in the Bayan Mandahu Formation, it is likely that ''P. hellenikorhinus'' preferred environments combining [[Mesic habitat|humid]] and arid conditions.<ref>{{cite conference|last1=Chiba|first1=K.|last2=Ryan|first2=M. J.|last3=Saneyoshi|first3= M.|last4=Konishi|first4=S.|last5=Yamamoto|first5=Y.|last6=Mainbayar|first6=B.|last7=Tsogtbaatar|first7=K.|date= 12–16 October 2020|title=Taxonomic re-evaluation of Protoceratops (Dinosauria: Ceratopsia) specimens from Udyn Sayr, Mongolia|conference=The Society of Vertebrate Paleontology 80th Annual Meeting|url=https://vertpaleo.org/wp-content/uploads/2021/03/SVP_2020_Program-Abstracts-Volume-FINAL-for-Publishing-1.27.2021.pdf|page = 104}}</ref>

===Taphonomy===
{{multiple image
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|image1=Standing Protoceratops - Tugrugeen Shireh, Gobi Desert 1971 2.jpg

|image2=Protoceratops specimen block MPC-D 100 526 individual B.png

|footer=''P. andrewsi'' individuals from Tugriken Shireh in an upwards crouched death pose; left specimen is also known as the "Standing Protoceratops"<ref name=Jerzykiewiczz1993/>
}}
In 1993 Jerzykiewiczz suggested that many articulated ''Protoceratops'' specimens died in the process of trying to free themselves from massive sand bodies that trapped them during sandstorms events and were not transported by environmental factors. He cited the distinctive posture of some ''Protoceratops'' involving the body and head arched upwards with forelimbs tucked in at their sides—a condition known as "standing" in particular cases—the absence of sedimentary structures in sediments preserving the individuals, and the Fighting Dinosaurs [[taphonomic]] history itself as evidence for this catastrophic preservation. Given that this posture is exhibited by populations from both Bayan Mandahu and Djadokhta formations, Jerzykiewiczz indicated that this behavior was not unique to any locality. He also considered it unlikely that these ''Protoceratops'' individuals died after burying themselves in the sand given that these specimens are only found in structureless sandstones; an arched posture would pose hard [[breathing]] conditions; and [[Fossorial|burrowers]] are known to excavate headfirst and sub horizontally.<ref name=Jerzykiewiczz1993/>

Fastovsky in 1997 examined the geology at Tugriken Shireh providing insights into the taphonomy of ''Protoceratops''. He agreed in that the preservation of ''Protoceratops'' specimens indicate that they underwent a catastrophic event such as desert storms, and carcasses were not relocated by scavengers or environmental factors. Several isolated burrows found in sediments at this locality have also been reported penetrating in the bone surface of some buried ''Protoceratops'' individuals. Fastovsky pointed out these two factors combined indicate that this site was host to high biotic activity, mainly composed of [[arthropod]] scavengers who were also involved in the recycling of ''Protoceratops'' [[Carrion|carcasses]]. The flexed position of most buried ''Protoceratops'' is indicative of [[desiccation]] and shrinking of [[ligament]]s/[[tendon]]s in the legs, necks, and tails after death.<ref>{{cite journal|last1=Fastovsky|first1=D. E.|date=1997|title=The Paleoenvironments of Tugrikin-Shireh (Gobi Desert, Mongolia) and Aspects of the Taphonomy and Paleoecology of Protoceratops (Dinosauria: Ornithishichia)|journal=PALAIOS|volume=12|number=1|pages=59–70|bibcode=1997Palai..12...59F|doi=10.2307/3515294
|jstor=3515294}}</ref>
[[File:Fox site Protoceratops (5).jpg|thumb|Cast of the Fox site ''Protoceratops'', a largely bored ''P. andrewsi'' (note reconstructed [[Rostrum (anatomy)|rostrum]])]]
In 1998 during a conference abstract at the [[Society of Vertebrate Paleontology]], [[James I. Kirkland]] and team reported multiple arthropod pupae casts and borings (tunnels) on a largely articulated ''Protoceratops'' specimen from Tugriken Shireh, found in 1997. A notorious amount of [[pupa]]e were found in clusters and singly along the bone surfaces, mostly in the joint areas, where the trace makers would have feed on dried ligaments, tendons and [[cartilage]]. The examined pupae from the specimen are more cylindrical structures with rounded ends. The pupae found in this ''Protoceratops'' individual were reported as measuring as much a {{convert|2.5|cm|mm|abbr=on}} long and {{convert|1|cm|mm|abbr=on}} wide and compare best with pupae attributed to [[Hunting wasp|solitary wasps]]. Additionally, the reported borings have a structure that differs from traces made by [[dermestid]] [[beetles]]. The team indicated that both pupae and boring traces reflect a marked ecological relationship between dinosaur carcasses and a relatively large [[necrophagous]] insect taxon.<ref>{{cite journal|last1=Kirkland|first1=J. I.|last2=Delgado|first2=C. R.|last3=Chimedtseren|first3=A.|last4=Hasiotis|first4=S. T.|last5=Fox|first5=E. J.|date=1998|title=Insect? bored dinosaur skeletons and associated pupae from the Djadokhta Fm. (Cretaceous, Campanian), Mongolia|journal=Journal of Vertebrate Paleontology|volume=18|issue=supp. 003|page=56A|doi=10.1080/02724634.1998.10011116|jstor=i406883|url=https://www.researchgate.net/publication/301626260}}</ref>

Later in 2010, Kirkland and Kenneth Bader redescribed and discussed the numerous feeding traces from this ''Protoceratops'' specimen, which they nicknamed Fox Site ''Protoceratops''. They found at least three types of feeding traces on this individual; nearly circular borings—which they found instead to correlate best with feeding traces made by dermestid beetles—of {{convert|0.6|-|1|cm|mm|abbr=on}} in diameter; semicircular shaped notches at the edge of bones; and destruction of articular surfaces, mostly at the [[joint]]s of the limbs. The co-workers also noted that the Fox Site ''Protoceratops'' preserves associated traces in the encasing sediment, indicative of necrophagous activity after the animal was buried. Kirkland and Bader concluded that adults of a large [[beetle]] taxon would detect [[Decomposition|decaying]] carcasses buried below the sand and dig down to feed and lay their eggs. After emerging from the eggs, [[larvae]] would have fed on the carcass prior to pupating. The last larvae to emerge would have feed on the dried tendons and cartilage in the joint areas—thereby explaining the notorious poor preservation of these areas in the specimen—and subsequently chewing on the bone itself, prior to pupating. After reaching full maturity, adult beetles would have then dig back to the surface, most likely leaving borings through bones, and finally beginning to search for new carcasses and thus continuing the recycling of ''Protoceratops'' carcasses.<ref>{{cite book|last1=Kirkland|first1=J. I.|last2=Bader|first2=K.|year=2010|chapter=Insect Trace Fossils Associated with Protoceratops Carcasses in the Djadokhta Formation (Upper Cretaceous), Mongolia: Forensic Entomology in the Upper Cretaceous|chapter-url=https://www.academia.edu/228136|editor-last1=Ryan|editor-first1=M. J.|editor-last2=Chinnery-Allgeier|editor-first2=B. J.|editor-last3=Eberth|editor-first3=D. A.|title=New Perspectives on Horned Dinosaurs: The Royal Tyrrell Museum Ceratopsian Symposium|publisher=Indiana University Press|pages=509–519|jstor=j.ctt16gzgng|isbn=9780253353580 }}</ref>

[[File:Protoceratops specimen MPC-D 100 534 skull.png|thumb|left|''P. andrewsi'' specimen MPC-D 100/534; note borings on the rostrum]]

In 2010 the paleontologists Yukihide Matsumoto and Mototaka Saneyoshi reported multiple borings and bite traces on joint areas of articulated ''Bagaceratops'' and ''Protoceratops'' specimens from the Tugriken Shireh locality of the [[Djadokhta Formation]] and Hermiin Tsav locality of the [[Barun Goyot Formation]], respectively. They interpreted the damaged areas in the ''Protoceratops'' specimen as product of active feeding by burrowing arthropods, most likely insects.<ref>{{cite journal|last1=Matsumoto|first1=Y.|last2=Saneyoshi|first2=M.|date=2010|title=Bored dinosaur skeletons|journal=The Journal of the Geological Society of Japan|volume=116|number=1|pages=I-II|doi=10.5575/geosoc.116.1.I_II|doi-access=free|url=https://www.jstage.jst.go.jp/article/geosoc/116/1/116_116.1.I_II/_pdf}}</ref> These specimens were formally described and discussed in 2011 by Saneyoshi and team, including fossils from ''[[Velociraptor]]'' and an [[ankylosaurid]]. Reported traces were identified as pits, notches, borings, and channels across the skeletons, most notably at limb joint areas. The team indicated that it is very likely that these were made by scavenging insects, however, relatively large borings (about {{convert|3|cm|mm|abbr=on}} wide) in the ribs and scapulae of one ''Protoceratops'' specimen (MPC-D100/534) indicates that insects were not the only scavengers involved in the bone damage, but also [[mammal]]s. Given the dry/harsh paleoenvironmental conditions of units like the Djadokhta Formation, medium to large-sized dinosaur carcasses may have been an important source of nutrition for small animals. Saneyoshi and team emphasized that the high frequency of feeding traces at the limb joints of numerous specimens and reports of previous studies, indicates that small animals may have targeted the [[collagen]] found in the joint cartilage of dried dinosaur carcasses as a source of [[nitrogen]], which was low in the desert-dry conditions of these dinosaur fossils.<ref>{{cite journal|last1=Saneyoshi|first1=M.|last2=Watabe|first2=M.|last3=Suzuki|first3=S.|last4=Tsogtbaatar|first4=K.|date=2011|title=Trace fossils on dinosaur bones from Upper Cretaceous eolian deposits in Mongolia: Taphonomic interpretation of paleoecosystems in ancient desert environments|journal=Palaeogeography, Palaeoclimatology, Palaeoecology|volume=311|issue=1–2|pages=38–47|bibcode=2011PPP...311...38S|doi=10.1016/j.palaeo.2011.07.024|url=https://www.academia.edu/27857932}}</ref>

[[File:Protoceratops specimen block MPC-D 100 526 individual C.png|thumb|Juvenile from MPC-D 100/526; black arrow points to larvae borings]]

In 2011 Fastovsky with colleagues concluded that the juveniles within the nest MPC-D 100/530 were rapidly overwhelmed by a strong sand-bearing event and entombed alive. The sediments of the nest suggest a deposition through a dune-shift or strong sandstorms, and the orientation of the individuals indicates that sediments were brought from a prevailing west-southwest wind. Most individuals are preserved with their forelimbs splayed and hindlimbs are extended, an arrangement that suggests that young ''Protoceratops'' tried to push against the powerful airstream in the initially loose sand. Prior to or during burial, some may have tried to climb on top of others. Because it is generally accepted that most fossil specimens at Tugriken Shireh were preserved by rapidly migrating dunes and sandstorms, Fastovsky with colleagues suggested that the lee side borders of the nest would have been the area where air was sand-free and consequently, all young ''Protoceratops'' may have struggled to reach this area, resulting in their final burial and eventual death.<ref name=Fastovsky2011/>

Hone and colleagues in 2014 indicated that two assemblages of ''Protoceratops'' at Tugriken Shireh (MPC-D 100/526 and 100/534) suggest that individuals died simultaneously, rather than accumulating over time. For instance, the block of four juveniles preserves the individuals with near-identical postures, spatial positions, and all of them have their heads facing upwards, which indicates that they were alive at the time of burial. During burial, the animals were most likely not completely restricted in their movements at all, given that the individuals of MPC-D 100/526 are in relatively normal life positions and have not been disturbed. At least two individuals within this block are preserved with their arms at a level above the legs, suggestive of attempts of trying to move upwards with the purpose of free themselves. The team also noted the presence of borings on the skulls and skeletons of both assemblages, and these may have been produced by insect larvae after the animals died.<ref name=Hone2014/>

In 2016 Meguru Takeuchi and team reported numerous fossilized feeding traces preserved on skeletons of ''Protoceratops'' from the Bayn Dzak, Tugriken Shireh, and Udyn Sayr localities, and also from other dinosaurs. Preserved traces were reported as pits, notches, borings, and tunnels, which they attributed to scavengers. The diameter of the feeding traces preserved on a ''Protoceratops'' skull from Bayn Dzak was bigger than traces reported among other specimens, indicating that the scavengers responsible for these traces were notoriously different from other trace makers preserved on specimens.<ref>{{cite journal|last1=Takeuchi|first1=M.|last2=Saneyoshi|first2=M.|last3=Tsogtbaatar|first3=K.|last4=Mainbayar|first4=B.|last5=Ulziitseren|first5=S.|date=2016|title=Trace fossils on dinosaur skeletons from the Upper Cretaceous of Gobi desert, Mongolia|journal=Bulletin of Research Institute of Natural Sciences, Okayama University of Science|number=46|pages=1–6|url=https://drive.google.com/file/d/1d1h9glLjUnyUSPhE1Kky9HRq7Tnmiud7/view}}</ref>