Paleontologists have unearthed two exceedingly rare skulls of a titanosaur, finally putting a face on one of the world's most common, yet least understood dinosaurs.
The skulls' discoveries in Madagascar also fuel the debate over how dinosaurs spread around the world and when the Earth's land masses split into today's arrangement of continents.
One of the fossils — a juvenile — is 90 percent complete, including the skull, making it perhaps the best example of a titanosaur ever found. The second specimen is an adult skull only.
The fossils, described in the current issue of the journal Nature, are 65 million to 70 million years old. Most titanosaurs, like other plant-eating behemoths, lived up to 140 million years ago.
The relative youth of these specimens suggests that titanosaurs spanned several periods of dinosaur evolution until all dinosaurs went extinct at the end of the Cretaceous Period.
"These animals were extremely successful, the dominant plant-eaters in some parts of the world," said Scott Sampson, paleontology curator at the Utah Museum of Natural History. Sampson participated in the Madagascar dig, but did not contribute to the study.
"By figuring out relationships between titanosaurs around the world, we can understand the breakup of the continents," Sampson said. "That helps to make this a great discovery."
Titanosaur Bones Found on Six Continents
The first titanosaur was found in 1842. Since then, their bones have been located on every continent except Antarctica.
Titanosaurs are not one species, but a group of at least 30 herbivores of different sizes. The largest is Argentinosaurus. Found in Patagonia, it was 90 feet (27 meters) long and weighed 90 tons, making it the largest creature to ever walk the Earth.
Titanosaurs belonged to a larger category of lightly armored dinosaurs known as sauropods — prototypical plant-eaters with long necks and tails, huge bodies and pile-driver legs. Most sauropods lived during the Jurassic Era, dying out more than 100 million years ago. But titanosaurs persisted.
Titanosaurs are poorly understood. That's because their heads were small and delicate, easily snapping off after death.
"We've never had a complete picture of a titanosaur before," said the study's lead author, Kristina Curry Rogers of the Science Museum of Minnesota in St. Paul.
"This tells us what they looked like," she said, "from the light head hanging on the end of a long neck to the tip of its tail."
Species Had Strong Sense of Smell
The Madagascar specimens probably grew to 50 feet (15 meters). Their scientific name is Rapetosaurus krausei. Rapetosaurus reflects the role of Rapeto, a mythical giant, in the folklore of Madagascar. Krausei honors paleontologist David Krause.
The titanosaur skulls have distinctive features.
The heads are less than 2 feet (60 cms) long with horse-like jaws. Cylindrical teeth resembling sharp pencils were used to strip leaves off branches.
The nostrils are located high on the snout. Large nerve channels suggest it smelled keenly.
High on the face sit two large gaps in the thin skull. They resemble huge eye sockets, but scientists believe they worked like sinuses.
The fragmented skulls were chipped from an ancient river channel in northwest Madagascar beginning in 1995. They were reassembled in the laboratory.
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Posted by Dinosaurs World at 9:25 PM