Mesozoic Era: Jurassic Period 

201–145 Ma

The Jurassic: an age of beasts

Made famous, at least in name, by the Jurassic Park series, the Jurassic Period began like several others thus far—in the aftermath of a mass extinction. The Triassic-Jurassic extinction event was likely triggered by the eruption of the Central Atlantic Magmatic Province (also known as the CAMP). This extinction wiped-out most of the non-dinosaurian archosaurs, many synapsid ancestors to the mammals, and most of the large amphibians, which left the terrestrial realm dominated by the dinosaurs and pseudosuchian archosaurs (those more closely related to crocodilians than birds). A few tens of millions of years later, the Toarcian Oceanic Anoxic Event acidified the oceans and caused even more mass die-offs in the oceans, and was also likely caused by large-scale volcanism, this time related to the Karoo-Ferrar large igneous provinces of southern Africa and Antarctica. The high level of volcanic activity was tied to the supercontinent cycle during this period, with the break-up of Pangea into Laurasia (present-day broken into North America, Europe, and most of Asia) moving to the northern hemisphere and Gondwana (present-day South America, Africa, Australia, India, and Antarctica) moving to the southern hemisphere. Crocodylomorphs made their way back into the water, joining other aquatic reptiles of the time like the long-necked plesiosaur (left) and large predatory mosasaur (right), as shown here. On land, conifers were one of the most significant components of the flora, including the first records of cypress trees. Ginkgos and cycads reached peak levels of diversity. In the skies, pterosaurs were the earliest known archosaurs to have evolved wing-powered flight rather than simple gliding. In the background, two feathered Archaeopteryx, generally acknowledged as the earliest birds, fight for dominance. Don’t worry about that ceratopsian in the foreground just yet, he's a personal favorite, but we’ll talk about him shortly in the Cretaceous—the animals then were just too big to contain within a single frame! Nevertheless, his ornithischian (or, “bird-hipped”, but confusingly not directly related to birds...) ancestors made their first appearances here in the Jurassic. Amongst them, the roots of the marginocephalians (those with "fringed heads") appeared here towards the end of the Jurassic, with early representatives like Chaoyangsaurus and Psittacosaurus, and the group diversified in the early Cretaceous, including both the horn-faced ceratopsians and the thick-headed pachycephalosaurians.