Dino of the Week: Patagosaurus

Type Species: Patagosaurus fariasi

Classification: Dinosauria – Saurischia – Sauropoda – Gravisauria - Eusauropoda - Cetiosauridae

Time Period: Middle Jurassic

Location: South America (Argentina)

Diet: Herbivore 

Patagosaurus lived in the southwest of Gondwana, and it’s known from several specimens, including one juvenile. This sauropod had a long neck; a small head with a short, high, broad snout; and a very long tail. The juvenile specimen exhibits features different from the adults in the mandible, pectoral girdle, pelvis, and hind limbs. An adult Patagosaurus grew to fifty-four feet in length and weighed seven and a half tons. Its teeth were like those of more derived sauropods, similar in morphology to Euhelopus, being concave on one side and having fairly-expanded crowns; the teeth are also similar to Camarasaurus, though with less concavity and expansion. Patagosaurus’ neural canal of the vertebrae is unique among sauropods, however: starting from the very end of the first vertebra, and extending to almost the end of the third, there’s an enlargement of the canal that forms a well-defined cavity. In a lot of ways Patagosaurus resembled the North American sauropod Haplocanthosaurus, though it was still more primitive. Patagosaurus and its kin may be the direct ancestors of some of the largest Late Jurassic sauropods. Though the continents were splitting and moving farther away from each other, it is possible that towards the end of the Middle Jurassic and the beginning of the Late Jurassic, there were land connections that enabled sauropods to travel between Gondwana and northern Laurasia; this seems to be the case, as members of the same ‘sauropod family’ have been found in these different places.

Patagosaurus was discovered in the Canadon Asfalto Formation in Argentina, which gives us an exquisite snapshot of the Callovian stage of the Middle Jurassic. One researcher 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 assemblage of fossils allows us to get a pretty accurate picture of what the environment was like back then. During the late Middle Jurassic and early Late Jurassic, the plants of this area were largely conifers, though ferns are also abundant. Directly beneath the formation is a layer of ash, indicating a nearby volcano (not surprising, given the intense amount of volcanic activity in the Jurassic due to the splitting of the supercontinents). Terrestrial organisms in this lush, tropical environment include the primitive frog Notobatrachus, the turtle Condorchelys, the lizard-like rhynchocephalian Sphenocondor, and a numerous small, early mammals such as Argentoconodon, Asfaltomylos, and Henosferus. The largest creatures were, of course, the dinosaurs. These include the sauropods Patagosaurus and Volkheimeria; the herbivorous heterodont Manidens is also represented, and scientists theorize that it was an arboreal (tree-dwelling) dinosaur due to its feet, which were structured like those of tree-perching birds. Theropods of the environment included Condorraptor, the abelisaur Eoabelisaurus, and the early allosaur Asfaltovenator. The apex predator of the day was Piatnitzkysaurus, who grew as large as the Late Jurassic Allosaurus and was the prime menace to South American herbivores. The small pterosaur Allkaruen flitted about the trees above the heads of these terrestrial dinosaurs.