Editing Tyrannosaurus (section)

===''Tyrannosaurus mcraeensis''===
[[File:Tyrannosaurus mcraeensis (skull reconstruction).png|thumb|Reconstructed skull of ''T. mcraeensis'']]
In 2024, Dalman and colleagues [[Species description|described]] the remains of a tyrannosaur discovered in 1983 in the Campanian-early Maastrichtian [[Hall Lake Formation]] in New Mexico. Reposited at the [[New Mexico Museum of Natural History and Science]], the fossil material (NMMNH P-3698) consists of the right [[postorbital]], right [[squamosal]], left [[palatine]], and an incomplete [[maxilla]] from the skull, the left [[dentary]], right [[splenial]], right prearticular, right [[Angular bone|angular]] and right [[articular]] from the lower jaws, isolated teeth, and [[Haemal arch|chevron]]s.<ref name=T.mcraeensis>{{Cite journal |last1=Dalman |first1=Sebastian G. |last2=Loewen |first2=Mark A. |last3=Pyron |first3=R. Alexander |last4=Jasinski |first4=Steven E. |last5=Malinzak |first5=D. Edward |last6=Lucas |first6=Spencer G. |last7=Fiorillo |first7=Anthony R. |last8=Currie |first8=Philip J. |last9=Longrich |first9=Nicholas R. |date=January 11, 2024 |title=A giant tyrannosaur from the Campanian–Maastrichtian of southern North America and the evolution of tyrannosaurid gigantism |journal=Scientific Reports |language=en |volume=13 |issue=1 |page=22124 |doi=10.1038/s41598-023-47011-0 |issn=2045-2322|pmid=38212342 |doi-access=free|pmc=10784284 }}</ref> Some of the bones were briefly mentioned in 1984 as belonging to ''T. rex'',<ref name=Lozinsky1984>{{Cite journal |last1=Lozinsky |first1=Richard P. |last2=Hunt |first2=Adrian P. |last3=Wolberg |first3=Donald L. |last4=Lucas |first4=Spencer G. |year=1984 |title=Late Cretaceous (Lancian) dinosaurs from the McRae Formation, Sierra County, New Mexico |journal=New Mexico Geology |language=en |volume=6 |issue=4 |pages=72–77 |doi=10.58799/NMG-v6n4.72 |s2cid=237011797 |url=https://geoinfo.nmt.edu/publications/periodicals/nmg/6/n4/nmg_v6_n4_p72.pdf |issn=0196-948X |archive-date=November 18, 2023 |access-date=January 12, 2024 |archive-url=https://web.archive.org/web/20231118063409/http://geoinfo.nmt.edu/publications/periodicals/nmg/6/n4/nmg_v6_n4_p72.pdf |url-status=live }}</ref> and described in 1986.<ref name=Gillette1986>{{Cite journal |last1=Gillette |first1=David D. |last2=Wolberg |first2=Donald L. |last3=Hunt |first3=Adrian P. |year=1986 |title=''Tyrannosaurus rex'' from the McRae Formation (Lancian, Upper Cretaceous), Elephant Butte reservoir, Sierra County, New Mexico |journal=New Mexico Geological Society Guidebook |language=en |volume=37 |pages=235–238 |doi=10.56577/FFC-37.235 |s2cid=251985284 |url=https://nmgs.nmt.edu/publications/guidebooks/downloads/37/37_p0235_p0238.pdf |archive-date=January 12, 2024 |access-date=January 12, 2024 |archive-url=https://web.archive.org/web/20240112195843/https://nmgs.nmt.edu/publications/guidebooks/downloads/37/37_p0235_p0238.pdf |url-status=live }}</ref>
[[File:Tyrannosaurus_mcraeensis.png|thumb|left|Life restoration of ''T. mcraeensis'']]
Lehman and Carpenter (1990) suggested that NMMNH P-3698 belonged to a new tyrannosaurid genus,<ref>{{cite journal |last=Lehman |first=Thomas M. |author2=Carpenter, Kenneth |author-link2=Kenneth Carpenter |year=1990 |title=A partial skeleton of the tyrannosaurid dinosaur ''Aublysodon'' from the Upper Cretaceous of New Mexico |journal=Journal of Paleontology |volume=64 |issue=6 |pages=1026–1032 |jstor=1305741 |doi=10.1017/S0022336000019843 |bibcode=1990JPal...64.1026L |s2cid=132662000 |url=https://zenodo.org/record/1037493 |archive-date=July 15, 2023 |access-date=March 17, 2024 |archive-url=https://web.archive.org/web/20230715174200/https://zenodo.org/record/1037493 |url-status=live }}</ref> while Carr and Williamson (2000) disagreed with their claim.<ref>{{cite journal | last1 = Carr | first1 = Thomas D. | last2 = Williamson | first2 = Thomas E. | date = 2000 | title = A review of Tyrannosauridae (Dinosauria: Coelurosauria) from New Mexico | publisher = [[New Mexico Museum of Natural History and Science]] | journal = Bulletin | volume = 17 | pages = 113–145 | url = http://econtent.unm.edu/cdm/ref/collection/bulletins/id/1015 }}</ref> Sullivan and Lucas (2015) argued that there is little evidence to support NMMNH P-3698 as a specimen of ''Tyrannosaurus rex'', so they tentatively classified it as cf. ''Tyrannosaurus'' sp.; they also considered that the McRae tyrannosaur lived before the [[Lancian]] (before 67 million years ago) based on its probable association with the ''[[Alamosaurus]]'' fossil.<ref>{{cite journal|last1=Sullivan|first1=Robert M.|last2=Lucas|first2=Spencer G.|year=2015|title=Cretaceous Vertebrates of New Mexico|journal=New Mexico Museum of Natural History and Science Bulletin|volume=68|url=https://www.researchgate.net/publication/299592501}}</ref>

Dalman et al. (2024) proposed the new name ''Tyrannosaurus mcraeensis'' for the holotype (NMMNH P-3698), referencing the McRae Group, the rock layers to which the Hall Lake Formation belongs. The holotype of ''T. mcraeensis'' is found in the strata that are around a few million years older than the accepted range of ''T. rex'', which existed at the end of the Maastrichtian. The rock layers were initially estimated to date to between 72.7 and 70.9 Ma, correlating to the latest Campanian or earliest Maastrichtian.<ref name=T.mcraeensis/> However, in a 2024 [[Academic conference|conference]] [[Abstract (summary)|abstract]]s, the specific stratigraphic layer which yielded ''T. mcraeensis'' was estimated to be younger than 69.0 ± 0.4 Ma and older than 66.0 Ma based on the sandstone from the same fossil locality,<ref>{{cite conference|author1=Schantz, E.|author2=Amato, J.M.|author3=Lawton, T.F.|title=Dating dinosaurs in the Laramide foreland: U-Pb geochronologic constraints on a stratigraphic section containing ''Alamosaurus'' and the postulated Tyrannosaurus mcraeensis in the Love Ranch Basin|conference=New Mexico Geological Society of America Abstracts with Programs|volume=56|pages=9}}</ref> which would suggest that the age of ''T. mcraeensis'' is much closer to ''T. rex'' than previously thought.<ref name=Scherer2025/> ''T. mcraeensis'' was estimated at {{convert|12|m|ft}} long, which is similar to the size of an adult ''T. rex''. The two are distinguished by characters of the skull. Amongst these, the dentary of ''T. mcraeensis'' is proportionately longer and possesses a less prominent chin, and the lower jaw shallower than that of ''T. rex'', suggesting a weaker bite. The teeth are likewise blunter and more laterally compressed, while the post orbital crests are less prominent. Likewise, the skeletal anatomy showcases shared characteristics with ''Tarbosaurus'' and ''Zhuchengtyrannus''.<ref name=T.mcraeensis/><ref name="NYT-20240111">{{cite news |last=Elbein |first=Asher |title=New Origin Story for ''Tyrannosaurus Rex'' Suggested by Fossil - Researchers say the species they named ''Tyrannosaurus mcraeensis'' predated the dinosaur era's great predator. |url=https://www.nytimes.com/2024/01/11/science/new-tyrannosaur-species-fossil.html |date=January 11, 2024 |work=[[The New York Times]] |url-status=live |archiveurl=https://archive.today/20240112033027/https://www.nytimes.com/2024/01/11/science/new-tyrannosaur-species-fossil.html |archivedate=January 12, 2024 |accessdate=January 12, 2024 }}</ref>

In 2025, Morrison and colleagues noted the uncertainty in the previous age estimate of ''T. mcraeensis''. In their supplementary material, the authors argued that the inclusion of the titanosaurian fossil (cf. ''Alamosaurus'') as a biostratigraphic marker of the Hall Lake Formation fauna makes the dating problematic due to the fossil having a huge variability in assumed sedimentation rates. The study also suggested the uncertainty in the morphology of ''T. mcraeensis'' holotype being reliably outside the known variation of ''T. rex''. Regardless of the age and validity of ''T. mcraeensis'', the authors concluded that the genus ''Tyrannosaurus'' still most likely originated from Laramidia and that the ancestors of this genus possibly migrated from Asia.<ref>{{cite journal|author1=Morrison, C.|author2=Scherer, C.R.|author3=O'Callaghan, E.V.|author4=Layton, C.|author5=Boisvert, C.|author6=Rolando, M.A.|author7=Durrant, L.|author8=Salas, P.|author9=Allain, S.J.R.|author10=Gascoigne, S.J.L.|year=2025|title=Rise of the king: Gondwanan origins and evolution of megaraptoran dinosaurs|journal=Royal Society Open Science|volume=12|issue=5|at=242238|doi=10.1098/rsos.242238|doi-access=free|pmid=40337259 |pmc=12055284}}</ref>