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. 

Cetiosaurus

Type Species: Cetiosaurus oxoniensis

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

Time Period: Middle Jurassic

Location: Europe (England) 

Diet: Herbivore 

Cetiosaurus was the first sauropod to be named. In 1841 Sir Richard Owen named it the ‘whale lizard’, as the fossils were thought to belong to a marine organism something along the lines of an extremely large crocodile. We now know that Cetiosaurus was a land-dwelling sauropod who lived in a floodplain environment with open woodlands. It was a contemporary of the theropod hunter Megalosaurus, which may have preyed upon Cetiosaurus. This sauropod had a shorter tail and neck than most sauropods, and the forelimbs were roughly the same size as its hind limbs. It could grow to about fifty-two feet long and weighed around eleven tons. Its dorsal vertebrae – the bones along the back – had the original heavy build with limited air chambers, unlike the hollowed-out bones of later sauropods. 

Barapasaurus

Type Species: Barapasaurus tagorei

Classification: Dinosauria - Saurischia - Sauropoda - Gravisauria - Cetiosauridae

Time Period: Early Jurassic

Location: India

Diet: Herbivore

The Early Jurassic sauropod Barapasaurus is one of the few dinosaurs that have been discovered on the Indian subcontinent. It lived during the Sinemurian and Pliensbachian stages of the Early Jurassic (199-182 million years ago). Over 300 Barapasaurus fossils were discovered in the Godavari Valley of south central Indian in 1961. The remains included no skulls or feet, but it was determined that the remains belonged to at least six individuals. The fossils were found among large tree trunks scattered over an area of over 250 square meters. Paleontologists speculate this assemblage was due to a catastrophic flood, in which the herd of these early sauropods in a conifer forest were swept away – along with the trunks of their foodstuffs – and deposited a distance away. As they began to decompose, the bones began to disarticulate, and the disarticulated skull bones were removed by the residual water streams because they were light. 

Barapasaurus was an early sauropod, and it exemplified many of the derived sauropod traits. An adult reached about sixty-six feet from head-to-tail, and it had the elongated neck and tail of the sauropods. It had a short trunk and columnar limbs. Its vertebrae show signs of transitioning to the type seen in more derived sauropods: though Barapasaurus had rudimentary weight-saving scoops or hollows common in sauropods, they were less prevalent than those found in later sauropods. Only three whole teeth and three crowns have been discovered. The largest known tooth is 5.8 centimeters in height. Its teeth were spoon-shaped and show wrinkled enamel, as is the case with derived sauropods. Barapasaurus was likely slow and plodding, feeding for many hours a day. It stripped vegetation and swallowed its food without chewing, allowing gastroliths in the gut to break down the food for processing.