Younginiformes is a group of diapsid reptiles known from the Permian-Triassic of Africa and Madagascar. It has been used as a replacement for "Eosuchia". Younginiformes (including Acerosodontosaurus, Hovasaurus, Kenyasaurus, Tangasaurus, Thadeosaurus and Youngina) were historically suggested to be lepidosauromorphs, but were later suggested to be basal non-saurian neodiapsids. The group is sometimes divided into two families, Tangasauridae and Younginidae. The monophyly of the group is disputed. A 2009 study found them to be an unresolved polytomy at the base of Neodiapsida, while a 2011 study recovered the group as paraphyletic. A 2022 study recovered the Younginiformes as a monophyletic group of basal neodiapsid reptiles, also including Claudiosaurus and Saurosternon as part of the group. Some younginiforms like Hovasaurus and Acerosodontosaurus are thought to have had an amphibious lifestyle, while others like Kenyasaurus, Thadeosaurus and Youngina were probably terrestrial.
Classification
Included genera:
Tangasauridae
Acerosodontosaurus
Hovasaurus
Kenyasaurus
Saurosternon? Tangasaurus Younginidae Claudiosaurus? Heleosuchus? Thadeosaurus Youngina
Phylogeny of Younginiformes from the 2022 study:
2011 phylogeny showing a paraphyletic Younginiformes: