Late Jurassic

Time-Span: 161 – 143 million years ago

Overview: The geological and fossil record from the Middle to Late Jurassic boundary suggests no major extinction events occurred, though there was a brief period of cooling at around that time which saw some changes in vegetation and weather. Afterward, however, global temperatures rose considerably and weather patterns appear to have been far more pronounced. This meant distinct and strong dry seasons, resulting in regional droughts, and powerful monsoons bringing denser vegetation. In terms of general groups, plants didn’t change very much going into the Late Jurassic, though some groups in and of themselves grew more abundant or “extreme” in other ways. Some truly enormous trees evolved in this time, further pushing the sauropods to evolve even larger bodies. Examples include China’s famous Mamenchisaurus, as well as more derived neosauropods. This included macronarian sauropods such as Camarasaurus and Brachiosaurus in North America, as well as diplodocoid sauropods. Some in the latter group, namely those in the family Diplodocidae like Apatosaurus and Diplodocus, were some of the longest sauropods ever recorded. Macronarians were generally more bulky, however.

Megalosaurid theropods, which had thrived during the Middle Jurassic, were somewhat less common going into the Late Jurassic. Some were still highly successful, however, as we can see with Torvosaurus – a genus that had a remarkably wide temporal and geographical range. By the end of the period, most of the megalosaurids would die out, however. Allosauroids, on the other hand, continued to diversify into different families. This included the metriacanthosaurids like Sinraptor or Metriacanthosaurus itself, as well as the famous Allosaurus in the family Allosauridae. Allosaurus in particular was very successful, being one of the top predators in both North America and Europe. Ceratosaurs, a more basal theropod group, continued to flourish, exemplified by Ceratosaurus and the more bizarre noasaurid ceratosaurs. Coelurosaurs, the bird line of theropods, were also going strong. This included early tyrannosaurs such as Guanlong and later Stokesosaurus, as well as more birdlike forms like Archaeopteryx in Europe. There is some evidence that spinosaurids, which may’ve been related to the megalosaurids, also evolved in this time, though this is debated. Most confirmed spinosaurids come from the Early Cretaceous.

Ornithischians continued their rapid diversification, with each group becoming more specialized in their own way. Stegosaurs were particularly successful in the Late Jurassic, with examples including Chinese taxa like Tuojiangosaurus, East Africa’s Kentrosaurus, Dacentrurus in Europe, and of course Stegosaurus itself in the United States. The latter two genera were particularly large and formidable, armed with long tail spines. Ankylosaur fossils are less common, but they were definitely present. They would enjoy more success in the Cretaceous, when the stegosaurs could enter a seemingly steep decline. Ornithopods were becoming more common, with examples including Dryosaurus and Camptosaurus. They tended to be smaller than their later relatives, usually retaining fully bipedal posture. This epoch would also see the emergence of the very first horned dinosaurs in Asia, which included taxa like Chaoyangsaurus and Yinlong. “Horned” isn’t entirely accurate, as these earliest ceratopsians lacked prominent horns and were by and large very small, bipedal creatures. What they lacked in horns they made up for with their sharp, parrot-like beaks, probably used to defend themselves from predators and to snap stems.

Among non-dinosaurian reptiles, the pterosaurs saw some notable changes. More “primitive”, long-tailed forms like Rhamphorhynchus still existed, though more derived short-tailed pterosaurs – those in the pterodactyloid lineage – would emerge. This included Pterodactylus and the filter-feeding pterosaur Ctenochasma. Most continued to be on the smaller side, however, like the short-snouted and rather bat-like anurognathid pterosaurs. Most marine reptile groups remained largely the same, though they too underwent changes, with some groups becoming more prominent than others. Mammals, or at least mammals in the broadest sense, had already evolved by this point. This epoch, however, did see some notable “experimentation” among them, entering new niches. Some gliding forms, similar to modern flying squirrels, are known from the Late Jurassic. Among amphibians, salamanders and frogs took on forms that were more and more similar to those we know today, though both lineages existed prior. Overall, we know far more about the Late Jurassic than we do of the previous epoch, largely due to there being many prominent formations like the Upper Shaximiao, Morrison, Tendaguru, and Lourinhã.

Notable Late Jurassic Dinosaurs: Tuojiangosaurus, Mamenchisaurus, Xiaotingia, Anchiornis, Yi, Limusaurus, Guanlong, Sinraptor, Yinlong, Metriacanthosaurus, Brachytrachelopan, Chaoyangsaurus, Haplocanthosaurus, Brontosaurus, Hesperosaurus, Gargoyleosaurus, Coelurus, Ornitholestes, Stokesosaurus, Marshosaurus, Brachiosaurus, Camarasaurus, Camptosaurus, Dryosaurus, Stegosaurus, Apatosaurus, Diplodocus, Barosaurus, Supersaurus, Ceratosaurus, Torvosaurus, Allosaurus, Turiasaurus, Europasaurus, Lourinhasaurus, Lourinhanosaurus, Zby, Dacentrurus, Giraffatitan, Dicraeosaurus, Tornieria, Kentrosaurus, Dysalotosaurus, Elaphrosaurus, Archaeopteryx, Compsognathus, etc.

Notable Late Jurassic Formations: Upper Shaximiao (China), Tiaojishan (China), Shishugou (China), Oxford Clay (United Kingdom), Cañadón Calcáreo (Argentina), Tuchengzi (China), Morrison (United States), Villar del Arzobispo (Spain), Süntel (Germany), Lourinhã (Portugal), Tendaguru (Tanzania), Altmühltal (Germany), Painten (Germany), etc.