有幾個學者都認為雙角龍可能是三角龍的直系祖先,或是其最近的近親。在傑克·霍納(John R. Horner)與約翰·斯堪那拉(John B. Scannella)的2010年研究中,除了提出牛角龍是三角龍的成年個體,也提出雙角龍是兩者之間的過渡階段[3]。他們是根據頭顱骨的鱗狀骨、頸盾緣骨突的形狀,以及頭盾有初步的洞孔。雙角龍的唯一頭顱骨,其實是三角龍從短頭盾、無洞孔,演化至長頭盾、雙洞孔的某個年齡階段[3]。他們並提出雙角龍缺乏鼻角,因在化石化過程中遺失了[3]。在2011年,Andrew Farke對此提出反對意見,認為這個頭顱骨有一定年齡、有足夠差異,應該是獨立屬[8]。
^Forster CA. Species resolution in Triceratops: cladistic and morphometric approaches. J.Vert.Paleont. 1996, 16 (2): 259–270.
^ 2.02.12.2(俄文)Ukrainsky, A.S. (2009). "Sinonimiya rodov Nedoceratops Ukrainsky, 2007 i Diceratus Mateus, 2008 (Reptilia: Ornithischia: Ceratopidae)." Paleontologicheskii zhurnal, 2009(1): 108. Translated as: Ukrainsky, A.S. (2009). "Synonymy of the genera Nedoceratops Ukrainsky, 2007 and Diceratus Mateus, 2008 (Reptilia: Ornithischia: Ceratopidae)." (页面存档备份,存于互联网档案馆) Paleontological Journal, 2009 43(1):116.
^ 3.03.13.23.33.4Scannella, John B.; Horner, John R. Torosaurus Marsh, 1891, is Triceratops Marsh, 1889 (Ceratopsidae: Chasmosaurinae): synonymy through ontogeny. Journal of Vertebrate Paleontology. 2010, 30 (4): 1157–1168. doi:10.1080/02724634.2010.483632.引文使用过时参数coauthors (帮助)
^Hatcher, John Bell. Two new Ceratopsia from the Laramie of Converse County, Wyoming. American Journal of Science. Series 4,. 1905, 4: 413−419 [2012-05-21]. (原始内容于2013-06-03).
^Lull, Richard Swann. Restoration of the horned dinosaur Diceratops. American Journal of Science. Series 4,. 1905, 4: 420−422 [2012-05-21]. (原始内容于2013-06-06).
^Ukrainsky, A.S. (2007). "A new replacement name for Diceratops Lull, 1905 (Reptilia: Ornithischia: Ceratopsidae)." (页面存档备份,存于互联网档案馆) Zoosystematica Rossica, 16(2), 20 December 2007: 292.
^(英文)Mateus, Octávio. Two ornithischian dinosaurs renamed: Microceratops Bohlin 1953 and Diceratops Lull 1905. Journal of Paleontology. 2008, 82 (2): 423. doi:10.1666/07-069.1.
^(英文)Farke, Andrew A. Claessens, Leon , 编. Anatomy and taxonomic status of the chasmosaurine ceratopsid Nedoceratops hatcheri from the Upper Cretaceous Lance Formation of Wyoming, U.S.A. PLoS ONE. 2011, 6 (1): e16196 [2012-05-21]. PMC 3024410. PMID 21283763. doi:10.1371/journal.pone.0016196. (原始内容于2012-06-07).
Dodson, Peter. The horned dinosaurs: a natural history. Princeton, NJ: Princeton University Press. 1996. ISBN 0-691-02882-6.
Forster, Catherine A. Species resolution in Triceratops: cladistic and morphometric approaches. Journal of Vertebrate Paleontology. 1996, 16: 259–270 [2012-05-21]. (原始内容于2022-02-17).