April 30, 2016

By David Templeton

Discovery of a nearly complete skull and neck fossil of a titanosaur, whose weight would have equaled that of two large elephants, is helping to explain the brains and brawn of the largest animals ever to walk on Earth.

It also reveals the physical demands of dinosaur hunting.

The Sarmientosaurus musacchioi fossil found in southen Argentina — in a remote and rocky area of central Patagonia described as a mini-Grand Canyon — required paleontologist Ruben D.F. Martinez of the National University of Patagonia and his team to hand-carry the 100-pound skull 2½ miles to their truck.

Removing the neck fossil still encased in rock required an Argentinian military helicopter.

But the paleontologists said the effort was well worth it, with what turned out to be arguably the most complete skull fossil of a titanosaur ever discovered. Already it has bolstered knowledge of long-necked, long-tailed dinosaurs with the full details published online Tuesday in the journal PLOS ONE.

Mr. Martinez, who holds a Ph.D., discovered the fossils of Sarmientosaurus — a rather small titanosaur at roughly 40 to 50 feet long and 10 tons.

His team included paleontologist Matt Lamanna, a titanosaur expert at the Carnegie Museum of Natural History, who helped with fossil analysis, and Lawrence Witmer, an Ohio University Heritage College of Osteopathic Medicine expert in dinosaur brains and skulls. The three announced the discovery Tuesday during a news conference at the museum in Oakland.

Research included a CT scan to detail the brain cavity and other parts of the skull. It also allowed completion of a 3D-printed model of the fossil, with the brain cavity serving as a mold to generate a 3D-printed model of the Sarmientosaurus brain, two of which could fit into one hand. Adding to the marvel is how these enormous animals survived many millions of years with a brain the size of an apple or large lime.

Mr. Martinez described the once-in-a-lifetime discovery as a means “to learn as much about this amazing animal as we could.”

Titanosaurs are plant-eaters with small heads, long necks and tails, column-like legs and truly massive bodies, representing what most people envision when hearing the word dinosaur. As a point of reference, Mr. Lamanna, who also holds a Ph.D., said Sarmientosaurus generally would have resembled Dippy the (Diplodocus) dinosaur outside of the Carnegie Museum.

Titanosaurs lived on every continent including Antarctica and ranged in weight from cow-sized to the weight of the largest sperm whale, he said.

Sarmientosaurus lived about 95 million years ago and despite its enormity was only a fraction of the weight and about half the length of the largest titanosaurs.

But knowledge of the more than 60 titanosaurs discovered to date has been limited with only three relatively complete skulls available prior to Sarmientosaurus. Its skull is providing a wealth of anatomical information, including details about brain size and function.

Its large eye sockets indicate good vision, with an inner ear thought to be ideal for hearing low-frequency airborne sounds. That likely meant the dinosaurs used low-frequency sound to communicate, although Mr. Witmer also noted the potential to hear the thunderous footsteps of other herd members.

The balance organ of the inner ear suggests that the dinosaur probably held its head downward, further suggesting it fed primarily on low-growing plants rather than browsing the trees for food.

“The skull is beautifully preserved, which meant that we could tease out a ton of information,” Mr. Witmer said.

“It was really exciting for us to work through the CT scan data because it gave us a glimpse into the biology and lifestyle of this animal like we rarely get with dinosaurs.”

The dinosaur’s genus was named after the town of Sarmiento in the Chubut Province of Argentina, which is close to the discovery site, while the species name (musacchioi) honors Eduardo Musacchio, a colleague of Mr. Martinez’s who was killed in a plane crash.

Mr. Lamanna has helped analyze other recent titanosaur discoveries in Argentina, including the huge Dreadnoughtus and Notocolossus, each weighing at least 40 tons and measuring up to 90 feet long.

In January, another team announced the discovery of what may be the largest ever land animal — a still unnamed Patagonian titanosaur that could have extended 122 feet and weighed up to 70 tons.

“My main role was to provide comparative context to other titanosaurs to help explain the new animal’s relationship to creatures found previously — in essence, where Sarmientosaurus sits on the evolutionary tree and how it compares to previously discovered titanosaurs,” he said.