Editing Troodon (section)

==Paleoecology==
[[File:Alaskan troodont.jpg|thumb|right|Restored skeleton of an unnamed Alaskan troodontid, [[Perot Museum]]]] 
The type specimen of ''Troodon formosus'' was found in the [[Judith River Formation]] of [[Montana]]. The rocks of the Judith River Formation are equivalent in age with the [[Oldman Formation]] of [[Alberta]],<ref name=eberth1997>{{cite book |last=Eberth |first=David A. |year=1997 |chapter=Judith River Wedge |editor=Currie, Philip J. |editor-link=Phil Currie |editor2=Padian, Kevin |title=Encyclopedia of Dinosaurs |url=https://archive.org/details/encyclopediadino00curr_075 |url-access=limited |publisher= Academic Press |location=San Diego |pages=[https://archive.org/details/encyclopediadino00curr_075/page/n229 199]–204 |isbn=978-0-12-226810-6}}</ref> which has been dated to between 77.5 and 76.5 million years ago.<ref name="ABS09">{{cite journal|last=Arbour, V.M.|author-link= Victoria Arbour|author2=Burns, M. E.|author3=Sissons, R. L.|year=2009|title=A redescription of the ankylosaurid dinosaur ''Dyoplosaurus acutosquameus'' Parks, 1924 (Ornithischia: Ankylosauria) and a revision of the genus|journal=Journal of Vertebrate Paleontology|volume=29|issue=4|pages=1117–1135| doi= 10.1671/039.029.0405|bibcode=2009JVPal..29.1117A |s2cid=85665879}}</ref>

In the past, remains have been attributed to the same genus as the Judith River ''Troodon'' from a wide variety of other geological formations. It is now recognized as unlikely that all of these fossils, which come from localities hundreds or thousands of miles apart, separated by millions of years of time, represent a single species or even a single genus of troodontid. Further study and more fossils are needed to determine how many species of ''Troodon'' existed. It is questionable that, after further study, any additional species can be referred to ''Troodon'', in which case the genus would be considered a ''[[nomen dubium]]''.<ref name=Talos>{{Cite journal|author=Lindsay E. Zanno, David J. Varricchio, Patrick M. O'Connor, Alan L. Titus and Michael J. Knell |year=2011 |title=A new troodontid theropod, ''Talos sampsoni'' gen. et sp. nov., from the Upper Cretaceous Western Interior Basin of North America |journal=PLOS ONE |volume=6 |issue=9 |pages=e24487 |doi=10.1371/journal.pone.0024487 |pmid= 21949721 |pmc=3176273|editor1-last=Lalueza-Fox|editor1-first=Carles| bibcode= 2011PLoSO...624487Z |doi-access=free }}</ref>

Remains referred to ''Troodon'' are known from the [[Prince Creek Formation]], a rock layer in Alaska that dates from the latest [[Campanian]] to [[Maastrichtian]] ages of the [[Late Cretaceous]].<ref name="braincase">{{cite journal|first1=A.R.|last1=Fiorillo |author-link=Anthony R. Fiorillo|first2=R.S.|last2=Tykoski|author-link2=Ronald S. Tykoski|first3=P.J.|last3=Currie|author-link3=Philip J. Currie|first4=P.J. |last4=Mccarthy |author-link4=Paul J. Mccarthy|first5=P.|last5=Flaig|s2cid=197535475|author-link5= Peter Flaig|year=2009|title=Description of two partial Troodon braincases from the Prince Creek Formation (Upper Cretaceous), North Slope Alaska|journal=Journal of Vertebrate Paleontology|volume=29|issue=1|pages=178–187|doi= 10.1080/02724634.2009.10010370|bibcode=2009JVPal..29..178F }}</ref> Based on the presence of [[gypsum]] and [[pyrite]] in the rocks, it suggests that the formation was bordered by a large body of water. It seems that, based on the presence of [[pollen]] fossils, the dominant plants were [[tree]]s, [[shrub]]s, [[herb]]s, and [[flowering plant]]s. The temperature ranged from possibly 2-12°C, which roughly correlates to 36-54°F, and based on Alaska's position in the late Cretaceous, the area faced 120 or so days of winter darkness.<ref>{{cite journal |last1=Druckenmiller |first1=Patrick S. |last2=Erickson |first2=Gregory M. |last3=Brinkman |first3=Donald |last4=Brown |first4=Caleb M. |last5=Eberle |first5= Jaelyn J. |date=23 August 2021 |title=Nesting at extreme polar latitudes by non-avian dinosaurs |journal=Current Biology |volume=31 |issue=16 |pages=3469–3478.e5 |doi=10.1016/j.cub.2021.05.041 |pmid=34171301 |s2cid=235631483|doi-access=free |bibcode=2021CBio...31E3469D }}</ref> This [[maniraptora]]n lived alongside many other reptiles, like the [[Centrosaurinae|centrosaurine]] ''[[Pachyrhinosaurus|Pachyrhinosaurus perotorum]]'', a species of the [[Saurolophinae|saurolophine]] [[Hadrosauridae|hadrosaurid]] ''[[Edmontosaurus]]'', the [[Pachycephalosauria|pachycephalosaurin]] ''[[Alaskacephale|Alaskacephale gangloffi]]'', an unnamed [[Azhdarchidae|azhdarchid]] [[pterosaur]], and the [[Tyrannosaurinae|tyrannosaurine]] ''[[Nanuqsaurus|Nanuqsaurus hoglundi]]''. It also lived alongside the [[Metatheria|metatherian]] mammal ''[[Unnuakomys|Unnuakomys hutchisoni]].''<ref>{{Cite journal |last1=Eberle |first1=Jaelyn J. |last2=Clemens |first2=William A. |last3=McCarthy |first3=Paul J. |last4=Fiorillo |first4=Anthony R. |last5=Erickson |first5=Gregory M. |last6=Druckenmiller |first6=Patrick S. |date=2019-02-14 |title=Northernmost record of the Metatheria: a new Late Cretaceous pediomyid from the North Slope of Alaska |url=https://www.tandfonline.com/doi/full/10.1080/14772019.2018.1560369 |journal=Journal of Systematic Palaeontology |volume=17 |issue=21 |pages=1805–1824 |doi=10.1080/14772019.2018.1560369 |bibcode=2019JSPal..17.1805E |issn=1477-2019 |s2cid=92613824|url-access=subscription }}</ref> Based on the amount of teeth found, this troodontid was the most common theropod of the [[Geological formation|formation]], making up 2/3 of all specimens, which is a stark contrast to more southern deposits in Montana, where troodontids only comprise 6% of all theropod remains.<ref name= ":02">{{Cite web |title=The giant troodontid dinosaurs of Alaska |url=https://eartharchives.org/articles/the-giant-troodontid-dinosaurs-of-alaska/index.html |website=eartharchives.org}}</ref> This, along with evidence that ''Troodon'' was more abundant during cooler intervals, such as the early Maastrichtian, may indicate that ''Troodon'' favored cooler climates.<ref name= "alaska">{{Cite journal | doi = 10.1671/0272-4634(2000)020[0675:TTFTPC]2.0.CO;2 | last1 = Fiorillo | first1 =  Anthony R.| last2 = Gangloff | first2 =  Roland A.| year = 2000 | title = Theropod teeth from the Prince Creek Formation (Cretaceous) of Northern Alaska, with speculations on Arctic dinosaur paleoecology | journal = Journal of Vertebrate Paleontology | volume = 20 | issue = 4| pages = 675–682 | s2cid = 130766946 }}</ref>

Additional specimens currently referred to ''Troodon'' come from the upper [[Two Medicine Formation]]<!-- nest site: Can. J. Earth Sci. 39: 19–26 (2002) --> of Montana. ''Troodon''-like teeth have been found in the lower [[Javelina Formation]] of [[Texas]] and the Naashoibito Member of the [[Ojo Alamo Formation]] in [[New Mexico]].<ref name="texas">Langston, Standhardt and Stevens, (1989). "Fossil vertebrate collecting in the Big Bend - History and retrospective." in ''Vertebrate Paleontology, Biostratigraphy and Depositional Environments, Latest Cretaceous and Tertiary, Big Bend Area, Texas''. Guidebook Field Trip Numbers 1 a, B, and 49th Annual Meeting of the Society of Vertebrate Paleontology, Austin, Texas, 29 October - 1 November 1989. 11-21.</ref><ref name="weil&williamson2000">Weil and Williamson, (2000). "Diverse Maastrichtian terrestrial vertebrate fauna of the Naashoibito Member, Kirtland Formation (San Juan Basin, New Mexico) confirms "Lancian" faunal heterogeneity in western North America." ''Geological Society of America Abstracts with Programs'', '''32''': A-498.</ref>