Researchers have completed a study on one of the few complete skulls of Sarmientosaurus muscacchioi, a titanosaurian sauropod dinosaur from the Upper Cretaceous period (about 95 million years ago). The study’s lead author, Ruben Martinez, director of the paleovertebrates lab at the National University of Patagonia San Juan Bosco in Argentina discovered the newfound skull and several neck vertebrae in 1997 in central Patagonia.
Though titanosuarian dinosaurs were one of the most massive animals to have ever roamed the earth, finding their heads are rare. Only three skulls have been discovered. Finding a sauropod skull to study has been hampered by the lack of a head on unearthed fossils. Thus, until now, little had been known about their lives and abilities.
Matthew Lamanna, the study co-author and assistant curator of vertebrate paleontology at the Carnegie Museum of Natural History in Pittsburgh says,
When you’ve got a river system, or any kind of environment where the water is moving quickly enough to transport enough sediment to bury one of these behemoths in time for it to be relatively well-preserved, oftentimes currents of that magnitude are probably going to wash away pretty small and delicate structures such as heads.
Titanosaur had a small head and brain in relationship to its large body. Researchers calculate the current specimen to have been about 40 feet long (12 meters) and weigh about 10 tons (9 metric tons). The skull is 17 inches (43 centimeters) long. The brain was about the size of a tennis ball.
Lawrence Witmer, an expert on cranial anatomy at Ohio University and the study’s senior author says,
The Sarmientosaurus skull is beautifully preserved, which means that we could tease out a ton of information.
Researchers ran the complete skull through a CT scanner to get a picture of its structure, including the brain case and inner ear. The scans showed that the sauropod had a hollow neck vertebrae, similar to that found in modern birds. A bony tendon within S. muscacchioi makes it the first non-avian dinosaur to have this unique structure, whose function is yet unknown.
Also discovered were that this species had large eye sockets. Big eyes denote the ability to find mates and avoid predators. They had an inner ear that was capable of detecting low-frequency sounds. Thus, they could communicate with one another. The inner ear also contained a balance organ that, in addition to its head and snout facing down, reveal that they fed on low-growing plants, rare in titanosaurs.
Results have also revealed that multiple titanosaurian species with dissimilar cranial and dental features co-existed in the early Late Cretaceous period.
Though the fossils remain in Argenitina, a 3-D printed replica of S. muscacchioi is on display at the Carnegie Museum of Natural History in Pittsburgh, Pennsylvania. A complete skeleton is at the American Museum of Natural History in New York City.