In particular, unlike other oviraptorids, the crest of Tongtianlong was shaped like a dome, with its highest point just behind the eye socket; and the front edge of the toothless premaxilla, which would have supported its beak, was very rounded.

Other characteristics of the skull separate Tongtianlong from its contemporaries; for instance, the nostril is situated much higher than the antorbital fenestra, a trait seen otherwise only in Nemegtomaia and Rinchenia.

[1] While the exceptionally well-preserved specimen was likely originally complete, portions of the arms, right leg, and tail were destroyed by the TNT blasting which unearthed the fossil.

It was first described and named by Lü Junchang, Chen Rongjun, Stephen L. Brusatte, et al.[1] In 2016, Tongtianlong was found to be a member of the Oviraptoridae, as a close relative of Banji and Wulatelong.

[1] Nankangia jiangxiensis Oviraptor philoceratops Yulong mini Nomingia mongoliensis Rinchenia mongoliensis Zamyn Khondt "Citipati" Huanansaurus ganzhouensis Citipati osmolskae Tongtianlong limosus Wulatelong gobiensis Banji long Shixinggia oblita Khaan mckennai Conchoraptor gracilis Wulatelong gobiensis Machairasaurus leptonychus Jiangxisaurus ganzhouensis Ganzhousaurus nankangensis Nemegtomaia barsboldi Ajancingenia yashini Heyuannia huangi Tongtianlong is the sixth oviraptorid described from the Nanxiong Formation, after Banji, Ganzhousaurus, Jiangxisaurus, Nankangia, and Huanansaurus, in that order.