the genera are more derived than Amygdalodon, yet more primitive than Haplocanthosaurus. Later in 1995, Paul Upchurch published a paper on early sauropods, finding Patagosaurus as a cetiosaurid again. He found that although earlier works had distinguished two groups, the shunosaurines and cetiosaurines, in the family, but that Shunosaurus and relatives were actually closer to Euhelopus, and cetiosaurines (Cetiosaurus, Patagosaurus and Amygdalodon) were the only true cetiosaurids. Upchurch noted, however, that further work on the group might reveal different conclusions. In a 2009 revision of Euhelopus, Jeffrey A. Wilson and Upchurch published a joint analysis on primitive eusauropodan relationships. They found that Patagosaurus was in fact not a sister taxon of Cetiosaurus, but instead more basal than the genus, effectively invalidating Cetiosauridae. Their results are shown below: A 2021 study found Patagosaurus to be a member of the Cetiosauridae. Paleoecology Patagosaurus was uncovered in the Middle Jurassic Cañadón Asfalto Formation, which preserves a large variety of flora and fauna. In fact, Escapa et al. noted that "the fossil record of this formation represents the most completely known biota from the continental Middle to Late Jurassic of the Southern Hemisphere and one of the most complete of the entire world". The Cañadón Asfalto Formation, which was deposited about 165 to 161 million years ago, was a lush ecosystem, in which many organisms lived. In the Middle Jurassic, the region would have been part of the great southern landmass of Gondwana. Most of the plants are conifers, although ferns and equisetales are also abundant. Directly below the formation is a layer of ash, indicating a nearby volcano. The fauna is dominated by tetrapods, ranging from aquatic amphibians to terrestrial turtles, mammals and dinosaurs. The sole amphibian known is Notobatrachus; turtles are represented by a distinct form that was named Condorchelys; mammals are known from a few genera, including Argentoconodon, Asfaltomylos and Henosferus; multiple dinosaurs have been identified, including the sauropods Volkheimeria, Patagosaurus and a potential third genus that is yet unnamed, and theropods include the related Piatnitzkysaurus and Condorraptor. References External links Cetiosauridae Dinosaur genera Middle Jurassic dinosaurs of South America Fossils of Argentina Jurassic Argentina Cañadón Asfalto Formation Fossil taxa described in 1979 Taxa named by José Bonaparte