Fossil remains of sauropods – dinosaurs with long necks and tails, weighing up to 100 tons – have been found on every continent but one.
Now, scientists report unearthing the first evidence of these animals in Antarctica, the last holdout.
The Argentine research team is reporting the discovery of a single vertebra and links it to a group of sauropods known as titanosaurs, hefty plant-eaters that were said to dominate the ranks of herbivores during their heyday between 90 million and 65 million years ago.
Titanosaurs appear to have been the last significant group of sauropods to emerge before dinosaurs were extinguished during a mass-extinction event some 65 million years ago.
The find, previewed at the Society of Vertebrate Paleontology's annual meeting in Las Vegas in early November, has just been formally published in the German journal Naturwissenschaften (The Science of Nature).
The team reporting the results unearthed the specimen from sediments near Santa Marta Cove on James Ross Island, a 1,000-square-mile patch of land sporting low mountains and curving bays near the tip of the Antarctic Peninsula.
Compared with the rest of the continent, capped with vast sheets of ice more than a mile thick, James Ross Island represents a fertile, if harsh, hunting ground for evidence of dinosaurs on the continent.
In 1986, a group of Argentine paleontologists reported uncovering what they termed the first confirmed dinosaur fossils on the continent, found on the island.
The likelihood that titanosaurs would have roamed what is now Antarctica was raised in 2007, the team notes, when another group of paleontologists found what it interpreted as a titanosaur vertebra in New Zealand. During the Cretaceous, the land of kiwis and "Lord of the Rings" was joined to Antarctica, providing ample opportunity for migration.
Indeed, the James Ross Island specimen appears to be the latest example of Cretaceous dinosaurs with a global reach.
The team suggests that titanosaurs, which have appeared in the fossil record in South America, among other continents, could have migrated to Antarctica when the two continents were joined by an isthmus during the late Cretaceous.
But the existence of the New Zealand fossil, as well as specimens in Australia, also suggests that the animals were widely distributed among the slowly diverging continents by then, the researchers add.
Given how sparse Antarctica's fossil record is compared with other continents, even the unearthing of a single fossil vertebra from a new group (for the continent) represents a step forward in reconstructing a more complete picture of prehistoric life at the bottom of the world, the team suggests.