Poposauroidea

Poposauroidea is a clade of advanced pseudosuchians. It includes poposaurids, shuvosaurids, ctenosauriscids, and other unusual pseudosuchians such as Qianosuchus and Lotosaurus. It excludes most large predatory quadrupedal "rauisuchians" such as rauisuchids and "prestosuchids". Those reptiles are now allied with crocodylomorphs (crocodile ancestors) in a clade known as Loricata, which is the sister taxon to the poposauroids in the clade Paracrocodylomorpha. Although it was first formally defined in 2007, the name "Poposauroidea" has been used for many years. The group has been referred to as Poposauridae by some authors, although this name is often used more narrowly to refer to the family that includes Poposaurus and its close relatives. It was phylogenetically defined in 2011 by Sterling Nesbitt as Poposaurus gracilis and all taxa more closely related to it than to Postosuchus kirkpatricki, Crocodylus niloticus (the Nile crocodile), Ornithosuchus woodwardi, or Aetosaurus ferratus. left|thumb|Skeletal reconstruction of Shuvosaurus|Shuvosaurus inexpectatus Poposauroids went extinct at the end of the Triassic period along with other non-crocodylomorph pseudosuchians. They were among the most diverse and longest lasting members of non-crocodylomorph Pseudosuchia, with Xilousuchus (a ctenosauriscid) living near the very beginning of the Triassic and Effigia (a shuvosaurid) surviving up until near the end of the Triassic. Despite the high level of diversity and anatomical disparity within Poposauroidea, certain features of the clade can be determined, particularly in the structure of the snout and pelvis (hip). Many of these features are examples of convergent evolution with dinosaurs, with bipedal poposauroids such as Poposaurus and shuvosaurids having been mistaken for theropod dinosaurs in the past.

== Features == thumb|Skeletal reconstruction of the known remains of Ctenosauriscus, showcasing its characteristic sailPoposauroidea was a diverse group of pseudosuchians, containing genera with many different ecological adaptations. Some (Poposaurus and shuvosaurids) were short-armed bipeds, while others (ctenosauriscids and Lotosaurus) were robust quadrupeds with elongated neural spines, creating a 'sail' like that of certain "pelycosaurs" (like Dimetrodon