雖然鐮刀龍的化石並不完整,但可參考其他鐮刀龍科來重建其特徵。如同其近親,鐮刀龍擁有小型頭部與喙狀嘴,以及長頸部。鐮刀龍是二足恐龍,從寬廣的骨盆可看出牠們擁有寬廣的大型身體。手臂長度為2.5公尺[4],甚至可達3.5公尺[7]。腳部上有4個腳趾,皆具承重性。第一趾爪略短,但與其他獸腳亞目不同,並未萎縮。2016年,美國現代古生物學先驅之一葛瑞格利·保羅(Gregory S. Paul)估計鐮刀龍的身長最高可達10公尺,體重至少有5噸。在鐮刀龍家族中是已知最大型的成員,甚至在手盜龍類中也位居第二(僅次於恐手龍)[7]。
^ 1.01.1Svarney, T.E. and Svarney, P.B. (2003). "The Handy Dinosaur Answer Book", 1st ed. Canton, MI: Visible Ink Press.
^ 2.02.1Barsbold, R. (1983). "Carnivorous dinosaurs from the Cretaceous of Mongolia [in Russian]." Trudy, Sovmestnaâ Sovetsko−Mongol’skaâ paleontologičeskaâ èkspediciâ, 19: 1–120.
^ 3.03.13.2Maleev, E.A. (1954). "New turtle−like reptile in Mongolia [in Russian]." Priroda, 1954(3): 106–108.
^ 4.04.1Barsbold, R. (1976c). "New data on Therizinosaurus (Therizinosauridae, Theropoda) [in Russian]." In Devâtkin, E.V. and N.M. Ânovskaâ (eds.), Paleontologiâ i biostratigrafiâ Mongolii. Trudy, Sovmestnaâ Sovetsko−Mongol’skaâ paleontologičeskaâ kspediciâ, 3: 76–92.
^Perle, A., 1982, "On a new finding of the hindlimb of Therizinosaurus sp. from the Late Cretaceous of Mongolia", Problems on the Geology of Mongolia, 5: 94–98
^ 6.06.1Rozhdestvensky, A.K. (1970). "On the gigantic claws of mysterious Mesozoic reptiles." Paleontologischeskii Zhurnal, 1970(1): 131-141.