cross-section. The tibia (shin bone) reached 84% of the length of the femur. Classification In a cladistic analysis, presented by Apaldetti and colleagues in November 2011, Sarahsaurus was found to be most closely related to Ignavusaurus within Massopoda. Their group was found to be intermediate between plateosaurids and massospondylids, being more derived than the former and more primitive than the latter. A 2018 cladistic analysis by Chapelle and Choiniere recovered Sarahsaurus and Ignavusaurus as massospondylids, mirroring the original assignment of Sarahsaurus to Massospondylus. Paleoecology Age and habitat A definitive radiometric dating of the Kayenta Formation has not yet been made, and the available stratigraphic correlation has been based on a combination of radiometric dates from vertebrate fossils, magnetostratigraphy and pollen evidence. It has been surmised that the Kayenta Formation was deposited during the Sinemurian and Pliensbachian stages of the Early Jurassic period, approximately 199 to 182 million years ago. The Kayenta Formation is part of the Glen Canyon Group that includes formations not only in northern Arizona but also parts of southeastern Utah, western Colorado, and northwestern New Mexico. The formation was primarily deposited by rivers. During the Early Jurassic, the land that is now the Kayenta Formation experienced rainy summers and dry winters. By the Middle Jurassic period it was being encroached upon from the north by a sandy dune field that would become the Navajo Sandstone. The animals here were adapted to a seasonal climate and abundant water could be found in streams, ponds and lakes. Paleofauna Sarahsaurus shared its paleoenvironment with other dinosaurs, such as several theropods including Dilophosaurus, Kayentavenator, Coelophyisis kayentakatae, and the "Shake N Bake" theropod, and the armored dinosaurs Scelidosaurus and Scutellosaurus. The Kayenta Formation has yielded a small but growing assemblage of organisms. Vertebrates present in the Kayenta Formation at the time of Saharasaurus included hybodont sharks, indeterminate bony fish, lungfish, salamanders, the frog Prosalirus, the caecilian Eocaecilia, the turtle Kayentachelys, a sphenodontian reptile, various lizards, and the pterosaur Rhamphinion. Also present were the synapsids Dinnebitodon, Kayentatherium, Oligokyphus, morganucodontids, the possible early true mammal Dinnetherium, and a haramiyid mammal. Several early crocodylomorphs were present including Calsoyasuchus, Eopneumatosuchus, Kayentasuchus, and Protosuchus. Vertebrate trace fossils from this area included coprolites and the tracks of therapsids, lizard-like animals, and dinosaurs, which provided evidence that these animals were also present. Non-vertebrates in this ecosystem included microbial or "algal" limestone, freshwater bivalves, freshwater mussels and snails, and ostracods.