The Titanosaurus is a name unfamiliar to most dinosaur fans despite the fact that it holds a unique place in dino history. It was the last surviving group of the giant four-legged sauropods when the dinosaurs went out with a bang 65 million years ago, most likely after a climate-changing meteorite smacked the earth.
The sauropods were the huge long-necked, long-tailed herbivores such as Brachiosaurus, Diplodocus or Apatosaurus, formerly Brontosaurus, that munched their way through the Jurassic and Cretaceous forests. While all the others are well represented and defined by fossil remains, complete Titanosaurus fossils have remained in short supply until now.
Dr Kristina Curry Rogers, now at the Science Museum of Minnesota, St Paul, and Dr Catherine A. Forster of the State University of New York at Stony Brook describe a Titanosaur skeleton recovered in the Maevarano Formation of Madagascar that affords a head-to-toe view of the beast's anatomy. They describe the find in the journal Nature.
The Titanosaurs were no fly-by-night operation. By the close of the Cretaceous period before the dinosaur days ended they had attained near global distribution. One problem with the Titanosaurs however was they apparently lost their heads after death. Many partial fossil skeletons were uncovered but researchers had little idea about what the whole animal looked like, particularly its head.
"With the exception of a few new discoveries in Argentina, most Titanosaurs are known only from fragmentary postcranial skeletons and rare, isolated skull elements," the authors write. The find, named Rapetosaurus krausei, included a disarticulated skull including all its elements and spread over no more than a square metre of ground. Parts from two juvenile skulls were recovered nearby with a near-complete juvenile skeleton.
Rapetosaurus is now well defined. It was an 8.5-metre long creature, a good bit shorter than the 22-metre Apatosaurus or the 26-metre Brachiosaurus. Its skeletal characteristics also allow palaeontologists to identify and link various species of Titanosaurus. The authors for example can now place the Mongolian fossils, Nemegtosaurus and Quaesitosaurus in the Titanosauria family.
The remains provide clues to the distribution of Rapetosaurus, which the authors particularly link to similar finds in Africa, Asia and India. "This finding contrasts with the proposed biogeographic history of Maevarano Formation mammals, crocodyliforms and theropod dinosaurs, which make a strong case for extensive faunal interchange between South America, India and Madagascar."
The creature's Latin name has strong links to Madagascar. Rapeto is the name given to a mischievous giant in Malagasy folklore. The second part of the name honours Professor David W. Krause of the University of Michigan, in recognition of his contributions to palaeontology in Madagascar during excavations and discoveries particularly during the 1990s.