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I would like to point out that there is no line numbers on your paper; also there is no visuals in this article.To help this problem find the pictures of the fossils in your paper.There is also no indentation to see when the paragraph starts. Next, there is no work cited page to be found and should added immediately. I do think most of the research is very sound so far yet you should go into further detail.
First off, the abstract did well to convene the general goal and content of the paper.
Additional anatomical references are recommended for each ontogenetic comparison.
A single comparison versus multiple comparisons to a theropod relatives better supports the argument.
On page 3, paragraph 3, elaborate on examples of young theropods with ontogenetic differences in the scapulocoracoid glenoid
The works cited should include a header. The title of books and paper should be consistently italicize for uniform citations. Scientific names of organisms should be italicized in the work cited
The science of the osteological and ontogenetic comparisons seem scientifically sound and well thought out. Looking at how you used other species that are tyrannosaurids or oviraptorosaurs, which are derived from tyrannosaurids. As well as the Tarbosaurus, which is a tyrannosaurid as well. Using species that are related to the Tyrannosaurus Rex supports your comparisons.
Very well-written and straight to the point to say the least, Mr. Yun! It does an excellent job of addressing the arguments brought to justify generic separation of "Nanotyrannus" from Tyrannosaurus, although there is still one factor that I feel you should address as well regarding supposed diagnostic features on "Nanotyrannus". This would be the difference in brain shape between the two taxa is used to justify the taxonomic validity of "Nanotyrannus", thus, I recommend citing this paper : http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0129939
Kawabe S, Matsuda S, Tsunekawa N, Endo H (2015) Ontogenetic Shape Change in the Chicken Brain: Implications for Paleontology. PLoS ONE 10(6): e0129939. doi:10.1371/journal.pone.0129939
It would further help with the case you are presenting, and also would help to clarify to anyone that brain morphology can change throughout ontogeny.
With respect to juvenile tyrannosaurs found in Lancian-age strata in western North America besides CMNH 7541 and Jane, Snively and Longrich (2009) report on an undescribed juvenile T. rex specimen (RSM P.2347.1) from the Frenchman Formation of Saskatchewan, which is ontogenetically intermediate between CMNH 7541 and LACM 28471 (holotype of Stygivenator molnari) (see http://tyrannosauroideacentral.blogspot.com/2014/12/the-jane-diaries-entries-36-43.html). Since you noted that contribution by Larson (2013) does not cite the description of juvenile Tarbosaurus by Tsuihji et al. (2011), it looks like you recognized the fact that even juvenile Tarbosaurus specimens have Gorgosaurus-like cranial features (e.g. T-shaped lacrimal), making it clear that juveniles of tyrannosaurine tyrannosaurids were somewhat morphologically similar to Gorgosaurus. Even though RSM P.2347.1 is undescribed, it may be useful to mention this specimen in your paper when discussing why Nanotyrannus is a T. rex juvenile.
Snively E. and Longrich N. 2009. A small juvenile tyrannosaurid specimen from the Frenchman Formation (Maastrichtian) of Saskatchewan. Frenchman Formation Terresrial Ecosystem Conference, Royal Saskatchewan Museum Contribution to Science Number 12: 46.
A new paper by Schmerge and Rothschild (2016) claims that Nanotyrannus is not just distinct from T. rex, but also an albertosaurine because CMNH 7541, Jane, and BHI 6437 have a dentary groove as in albertosaurines. However, the conclusions by Schmerge and Rothschild are complete bogus because those authors didn't examine the T. rex holotype or AMNH 5027 (both of which have a dentary groove; see http://tyrannosauroideacentral.blogspot.com/2016/01/by-way-that-groove-is-also-seen-in.html). Even worse, those authors don't mention the fact that the Tarbosaurus juvenile described by Tsuihji et al. (2011) has most of the cranial features that Larson (2013) used to distinguish Nanotyrannus from T. rex, including a T-shaped lacrimal. I discussed the paper by Schmerge and Rothschild with Stephen Brusatte and he totally agrees that Schmerge and Rothschild's paper is flawed and downplays the variability of the presence or absence of a dentary groove among tyrannosaurid specimens, including tyrannosaurines.
Joshua D. Schmerge & Bruce M. Rothschild (2016) Distribution of the dentary groove of theropod dinosaurs: Implications for theropod phylogeny and the validity of the genus Nanotyrannus Bakker et al., 1988. Cretaceous Research 61: 26-33 doi:10.1016/j.cretres.2015.12.016 http://www.sciencedirect.com/science/article/pii/S0195667115301415
Carr et al. (2017) note that the pneumatic foramen on the quadratojugal that Larson (2013) used to distinguish Nanotyrannus from T. rex is also present in Daspletosaurus horneri and the indeterminate specimen CMN 57080. Since you noted that the presence or absence of a pneumatic foramen varies among Gorgosaurus specimens, the pneumatic foramen could be synapomorphic for Tyrannosauridae.
Carr, Thomas D.; Varricchio, David J.; Sedlmayr, Jayc C.; Roberts, Eric M.; Moore, Jason R. (2017). "A new tyrannosaur with evidence for anagenesis and crocodile-like facial sensory system". Scientific Reports. 7: 44942. doi:10.1038/srep44942.
An SVP 2018 abstract by Burnham et al. (2018) reports that a juvenile T. rex specimen (KUVP 156375) found in Montana has the same maxillary count as adult T. rex (12 maxillary teeth), unlike the count of 15-16 maxillary teeth in the Nanotyrannus holotype and “Jane”. Because of the difference between KUVP 156375 and Jane in the maxillary tooth count despite both specimens being juvenile, KUVP 156375 helps clinch Carr's (1999) argument that Nanotyrannus is a juvenile T. rex because it is the first juvenile T. rex specimen to demonstrate a decrease in the number of maxillary teeth as T. rex individuals matured.
Burnham, Atkins-Weltman, and Jevnikar, 2018. A new juvenile Tyrannosaurus rex from the Hell Creek Formation of eastern Montana provides insights into cranial and dental ontogeny. SVP 78th annual meeting, Albuquerque, New Mexico, p. 99. (see http://vertpaleo.org/Annual-Meeting/Annual-Meeting-Home/SVP-2018-program-book-V4-FINAL-with-covers-9-24-18.aspx)
Carr (2020) has released a new paper on updates to knowledge of Tyrannosaurus rex ontogeny, including info on how maturity and decrease in tooth count are correlated in T. rex specimens, and this paper happens to mention the juvenile specimen RSM P.2347.1 (first discussed by Snively and Longrich 2009), corroborating the assessment by Snively and Longrich (2009) as younger than CMNH 7541 but older than LACM 28471.
Carr TD. 2020. A high-resolution growth series of Tyrannosaurus rex obtained from multiple lines of evidence. PeerJ 8:e9192 https://doi.org/10.7717/peerj.9192