Rapetosaurus ( ) is a genus of titanosaurian sauropod dinosaur that lived in Madagascar from 70 to 66 million years ago, at the end of the Cretaceous Period. Only one species, Rapetosaurus krausei, has been identified.
Like other sauropods, Rapetosaurus was a quadrupedal herbivore; it is calculated to have reached lengths of 15 metres (49 ft).
Description
Rapetosaurus was a fairly typical sauropod, with a short and slender tail, a very long neck and a huge, elephant-like body. Its head resembles the head of a diplodocid, with a long, narrow snout and nostrils on the top of its skull. It was a herbivore and its small, pencil-like teeth were good for ripping the leaves off trees but not for chewing.
It was fairly modest in size, for a titanosaur. The juvenile specimen measured from head to tail, and "probably weighed about as much as an elephant". An adult would have been about twice as long ( in length) which is still less than half the length of its gigantic kin, like Argentinosaurus and Paralititan. In 2020 Molina-Perez and Larramendi estimated the size of the probable adult specimen (MAD 93-18), which is known from a femur, at 16.5 meters (54 ft) and 10.3 tonnes (11.35 short tons).
Discovery and naming
The discovery of Rapetosaurus, known by the single species Rapetosaurus krausei marked the first time a titanosaur had been recovered with an almost perfectly intact skeleton, complete with skull. It has helped to clarify some difficult, century-old classification issues, among this large group of sauropod dinosaurs and provides a good baseline for the reconstruction of other titanosaurs that are known only from partial fossilized remains.
The discovery was published in 2001 by Kristina Curry Rogers and Catherine A. Forster in the scientific journal Nature. The nearly-complete skeleton is that of a juvenile and partial remains from three other individuals were also recovered.
The dig uncovered a partial skull (UA 8698, the holotype specimen), another partial skull, a juvenile skeleton missing only a few tail vertebrae, and an unrelated vertebra. The juvenile skeleton, in particular, is the most complete titanosaur skeleton ever recovered and the only one with a head still attached to the body.
The fossilized remains were found in the Mahajanga basin in northwest Madagascar, not far from the port city of Mahajanga. They were recovered from a layer of sandstone known as the Anembalemba Member, which is part of the Maevarano Formation. The rock formation has been dated to the Maastrichtian stage of the late Cretaceous, which means the fossilized bones are about 70 million years old. They were found by a field team from Stony Brook University with the assistance of the local Universite d'Antananarivo. The team leader, David Krause, had been excavating fossils from the site since 1993.
The generic name Rapetosaurus is derived from Rapeto (a giant deity in Malagasy folklore credited for the geographical features of the land) and sauros, which is Greek for lizard. The species epithet, krausei, is named after the team leader of the expedition, David W. Krause.
Paleobiology
Growth
A rare specimen of a juvenile Rapetosaurus was uncovered in a museum collection by Kristina Curry Rogers and colleagues. The specimen was estimated to weigh about 40 kilograms (88 pounds) and was likely between 39 and 77 days old by the time of its death. At the time of its hatching, the juvenile Rapetosaurus was estimated to be 3.4 kilograms (7.8 pounds) in weight. Based on bone remodeling, the juvenile sauropod was also believed to have been capable of surviving with little to no parental care. Analysis of the bones further revealed the young Rapetosaurus likely starved to death due to Cretaceous Madagascar's harsh droughts.