1914年發表加拿大有着拱形鼻部的鈎鼻龍,[7]改變了布朗對分離龍鼻部形象,他重新檢驗那些碎片,並修正之前的重建,賦予分離龍一個形似鈎鼻龍的拱形鼻部。[4]他還同時將鈎鼻龍視為分離龍的異名,[8]這得到查爾斯·惠特尼·吉爾摩的支持,[2]更於1920年代被廣泛採納,如威廉·帕克斯將加拿大物種定名為內彎手分離龍(Kritosaurus incurvimanus);[9]但現在被視為著名鈎鼻龍(Gryposaurus notabilis)的異名。[10]1942年李察·斯旺·盧爾(英語:Richard Swann Lull)與紐達·懷特(Nelda Wright)的北美洲鴨嘴龍科專著有着重大影響力,使分離龍=鈎鼻龍成為標準共識。[11]自此一直延續到1990年代,分離龍屬下至少涵蓋了模式種納瓦荷分離龍、內彎手分離龍、著名分離龍(K. notabilis,原鈎鼻龍的模式種)。而盧爾和懷特還將蒙大拿州坎潘階朱迪斯河層(英語:Judith River Formation)僅知齒骨、1889年由馬許命名的短頭鴨嘴龍(Hadrosaurus breviceps)[12]歸入分離龍,[11]時至今日則不再被承認。[13][14]
1970年代末至1980年代初,鴨嘴龍被牽扯進分離龍與鈎鼻龍的異名糾紛,尤其是在一些半學術性的恐龍百科。[15][16]大衛·諾曼(英語:David B. Norman)的《恐龍插畫百科》(The Illustrated Encyclopedia of Dinosaurs)中,把加拿大的鈎鼻龍化石稱為分離龍,並將內彎手分離龍的骨架稱為鴨嘴龍。[17]
起初霍納將阿納薩齊龍頭骨歸入納瓦荷分離龍,[23]但杭特及盧卡斯無法從分離龍的有限材料中發現明確的鑑定特徵,而視之為疑名。有鑑於阿納薩齊龍頭骨呈現出獨有衍徵,且與分離龍沒有任何共有衍徵,而得以獨立為新屬新種,[24]後續一些研究支持其論點,[13]但仍受到某些質疑,如托馬斯·威廉森(Thomas E. Williamson)支持霍納原先的解釋;[3]隨後幾項研究則承認兩者各自獨立。[25][26]
一個在墨西哥沙比納斯盆地(Sabinas Basin)發現的部分骨骼於2006年由詹姆斯·I·柯克蘭(英語:James I. Kirkland)等人稱為分離龍未命名種(Kritosaurus sp.),[25]但2013年皮耶妥馬奎茲認為這是櫛龍亞科未定種。[27]該骨骼的體型比其他已知標本大上20%,身長約11公尺,以坐骨彎曲為特徵,成為北美已知體型最大的櫛龍亞科之一。遺憾的是該標本也未能保存完整的吻部。[25]
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