懼龍通常被認為是暴龍的近親,或是往暴龍演化的直接祖先[11]。格里高利·保羅(Gregory S. Paul)曾將強健懼龍編入暴龍屬中[2],但這個分類卻一般不被接受[6][8]。很多學者認為特暴龍及暴龍是姊妹分類單元,或甚至是同屬,而懼龍是這個演化支的基礎物種[8][9]。菲力·柯爾(Phil Currie)等人提出一個不同的理論,分支龍與特暴龍這兩個亞洲屬構成一個演化支,而懼龍較接近這個演化支,而離北美洲的暴龍較遠[10]。要待所有的懼龍物種被研究、描述,才可以得到較清晰的懼龍分類關係。
^ 1.01.11.21.31.41.51.6(英文)Russell, Dale A. Tyrannosaurs from the Late Cretaceous of western Canada. National Museum of Natural Sciences Publications in Paleontology. 1970, 1: 1–34.
^(英文)Christiansen, Per; & Fariña, Richard A. Mass prediction in theropod dinosaurs. Historical Biology. 2004, 16 (2–4): 85–92. doi:10.1080/08912960412331284313.引文使用过时参数coauthors (帮助)
^ 4.04.1(英文)Erickson, Gregory M., GM; Makovicky, Peter J.; Currie, Philip J.; Norell, Mark A.; Yerby, Scott A.; & Brochu, Christopher A. Gigantism and comparative life-history parameters of tyrannosaurid dinosaurs. Nature. 2004, 430 (7001): 772–775. PMID 15306807. doi:10.1038/nature02699.引文使用过时参数coauthors (帮助)
^ 6.06.16.2(英文)Carr, Thomas D. Craniofacial ontogeny in Tyrannosauridae (Dinosauria, Coelurosauria). Journal of Vertebrate Paleontology. 1999, 19 (3): 497–520. doi:10.1080/02724634.1999.10011161.
^ 8.08.18.28.38.48.58.68.78.8(英文){{ref name=holtz2004>Holtz, Thomas R. Tyrannosauroidea. [Weishampel, David B.; Dodson, Peter; & Osmólska, Halszka (eds.). (编). The Dinosauria Second. Berkeley: University of California Press. 2004: 111–136. ISBN 0-520-24209-2.
^ 11.011.1(英文)Horner, John R.; Varricchio, David J.; & Goodwin, Mark B. Marine transgressions and the evolution of Cretaceous dinosaurs. Nature. 1992, 358 (6381): 59–61. doi:10.1038/358059a0.引文使用过时参数coauthors (帮助)
^(英文)Liddell & Scott. Greek-English Lexicon, Abridged Edition. Oxford University Press, Oxford, UK. 1980. ISBN 978-0-19-910207-5.
^(英文)Carr, Thomas D.; Williamson, Thomas E. A review of Tyrannosauridae (Dinosauria: Coelurosauria) from New Mexico. Lucas, Spencer G.; & Heckert, Andrew B. (eds.). (编). Dinosaurs of New Mexico. New Mexico Museum of Natural History and Science Bulletin17. 2000: 113–146.
^(英文)Carr, T.D.; Williamson, T.E. Bistahieversor sealeyi, gen. et sp. nov., a new tyrannosauroid from New Mexico and the origin of deep snouts in Tyrannosauroidea. Journal of Vertebrate Paleontology. 2010, 30 (1): 1–16. doi:10.1080/02724630903413032.
^(英文)Sullivan, Robert M.; & Lucas, Spencer G. The Kirtlandian land-vertebrate "age" – faunal composition, temporal position and biostratigraphic correlation in the nonmarine Upper Cretaceous of North America. Lucas, Spencer G.; & Sullivan, Robert M. (eds.). (编). Late Cretaceous vertebrates from the Western Interior. New Mexico Museum of Natural History and Science Bulletin35. 2006: 7–29.引文使用过时参数coauthors (帮助)
^ 20.020.120.2(英文)Currie, Philip J.; Trexler, David; Koppelhus, Eva B.; Wicks, Kelly; & Murphy, Nate. An unusual multi-individual tyrannosaurid bonebed in the Two Medicine Formation (Late Cretaceous, Campanian) of Montana (USA). Carpenter, Kenneth (ed.). (编). The Carnivorous Dinosaurs. Bloomington: Indiana University Press. 2005: 313–324. ISBN 978-0-253-34539-4.引文使用过时参数coauthors (帮助)
^(英文)Molnar, R. E. Theropod paleopathology: a literature survey. Tanke, D. H.; Carpenter, K.; Skrepnick, M. W. (编). Mesozoic Vertebrate Life. Bloomington: Indiana University Press. 2001: 337–363. ISBN 0253339073.
^ 23.023.123.2(英文)Farlow, James O.; & Pianka, Eric R. Body size overlap, habitat partitioning and living space requirements of terrestrial vertebrate predators: implications for the paleoecology of large theropod dinosaurs. Historical Biology. 2002, 16 (1): 21–40. doi:10.1080/0891296031000154687.引文使用过时参数coauthors (帮助)
^(英文)Eberth, David A.; & McCrea, Richard T. Were large theropods gregarious?. Journal of Vertebrate Paleontology. 2001, 21 ((Supplement to 3 - Abstracts of Papers, 61st Annual Meeting of the Society of Vertebrate Paleontology)): 46A.引文使用过时参数coauthors (帮助)[published abstract only]
^(英文)Roach, Brian T.; Brinkman, Daniel L. A reevaluation of cooperative pack hunting and gregariousness in Deinonychus antirrhopus and other nonavian theropod dinosaurs. Bulletin of the Peabody Museum of Natural History. 2007, 48 (1): 103–138.引文使用过时参数coauthors (帮助)
^(英文)Erickson, Gregory M.; Currie, Philip. J.; Inouye, Brian D.; & Wynn, Alice A. Tyrannosaur life tables: an example of nonavian dinosaur population biology. Science. 2006, 313 (5784): 213–217. PMID 16840697. doi:10.1126/science.1125721.引文使用过时参数coauthors (帮助)
^(英文)Falcon-Lang, Howard J. Growth interruptions in silicified conifer woods from the Upper Cretaceous Two Medicine Formation, Montana, USA: implications for palaeoclimate and dinosaur palaeoecology. Palaeogeography, Palaeoclimatology, Palaeoecology. 2003, 199 (3–4): 299–314. doi:10.1016/S0031-0182(03)00539-X.
^(英文)Jacobsen, A. R. Tooth-marked small theropod bone: An extremely rare trace. Tanke, D. H.; Carpenter, K.; Skrepnick, M. W. (编). Mesozoic Vertebrate Life. Bloomington: Indiana University Press. 2001: 58–63. ISBN 0253339073.