Fig. 55 in The Early Evolution Of Archosaurs: Relationships And The Origin Of Major Clades

Fig. 55. Relationships of Poposauroidea. The distribution of a ''sail'' (silhouette of the skeleton) and endentulism (drawing of the skull) is complex. A ''sail'' either evolved twice in poposauroids, once in Arizonsaurus + Xilousuchus, and once in Lotosaurus or the ''sail'' was lost independently in Poposaurus and Shuvosauridae.