Laurasia was the northern of the two great landmasses that Pangaea divided into. It carried what are now North America, Europe without the Balkan Peninsula, and Asia without India and Arabia, which still belonged to Gondwana in the south. It began to pull away from Gondwana in the late Triassic, between about 215 and 175 million years ago, and held together until the opening of the North Atlantic broke it in two about 56 million years ago. The name lives on in biology: a large branch of the mammal family tree, which includes bats, whales and horses, is called Laurasiatheria after it.
Laurasia is not Laurussia
The name joins Laurentia, the ancient core of North America, with Eurasia, and it is easily confused with an older, smaller continent. About 400 million years ago Laurentia collided with Baltica, the old core of north-western Europe, in the Caledonian mountain-building episode. The result was Laurussia, also called Euramerica or the Old Red Sandstone Continent, which in the late Carboniferous sat on the equator under tropical rainforest.
Laurasia was built on that core. Kazakhstania and Siberia were added from about 300 to 290 million years ago, and the long collision of Baltica, Kazakhstania and Siberia raised the Ural Mountains. Siberia had fused with Pangaea by about 250 million years ago. For tens of millions of years after that, these lands were simply the northern part of Pangaea. The partnership at the centre is far older: Laurentia had been the heart of the supercontinent Rodinia, and it and Baltica had drifted apart about 650 to 600 million years ago, opening the Iapetus Ocean that the Caledonian collision later closed.
Du Toit’s two halves
The idea of a northern continent came from the South African geologist du Toit, one of the staunchest supporters of Wegener’s continental drift. In his 1937 book Our Wandering Continents he proposed that Pangaea had been made of two large landmasses, Laurasia in the north and Gondwana in the south, with the Tethys Ocean between them. Rift basins opened between North America and Africa about 200 million years ago, ahead of the Central Atlantic, and by the Late Jurassic a seaway ran right across: Pangaea was in two.
Nor was Laurasia often a single unbroken landmass. The Turgai Strait separated Europe from Asia from the Middle Jurassic to the Oligocene, and in the warm, largely ice-free Cretaceous the sea rose so high that a third of today’s land area was flooded.
A sea through North America
The most striking of those floods was the Western Interior Seaway. For about 34 million years, from about 100 to 66 million years ago, it ran from the Gulf of Mexico to the Arctic Ocean and split North America into Laramidia in the west and Appalachia in the east, with Hudsonia to the north-east. At its largest it was roughly 760 m deep, 970 km wide and more than 3 200 km long. Mosasaurs and plesiosaurs hunted in it, along with the 4 to 5 m predatory fish Xiphactinus and the flightless bird Hesperornis, while Pteranodon flew overhead.
Torn open from the north
Laurasia’s final break came from the north. Seafloor spreading began in the North Atlantic about 83 million years ago, between the Rockall Basin and North America. By 56 million years ago Greenland had become a plate of its own, and by 33 million years ago spreading had moved from the Labrador Sea to the Mid-Atlantic Ridge. Land bridges still let animals cross in the early Paleogene, and early in the Eocene a peak of warmth brought alligators and amphibians north of the Arctic Circle.
Northern lineages
The northern dinosaur record starts early. Leg bones from Wyoming about 230 million years old, described in 2025 as Ahvaytum bahndooiveche, belong to the oldest known dinosaur from Laurasia, an animal its describers compared to a chicken with a very long tail. It argues against the idea that dinosaurs stayed in Gondwana for millions of years before spreading north.
Once the halves parted, the north went its own way. True crocodilians evolved from the Laurasian branch of their group, East Asia kept its own psittacosaurs and ankylosaurids, and the pine genus appeared about 130 million years ago, reaching from North America to East Asia by the end of the Cretaceous. Tyrannosaurs moved between the two ends: Khankhuuluu mongoliensis, a horse-sized relative of Tyrannosaurus about 90 to 83 million years old from Mongolia, suggests an ancestor reached North America from Asia about 85 million years ago and that the group later moved back.
