This tiny skull has big implications for the largest dinosaurs

Sauropods were the biggest dinosaurs – and the biggest land animals – ever to stomp across the planet. Their long-necked group included apatosaurus, brontosaurus, camarasaurus and the more massive titanosaurs, whose legions were longer than a tall person.

But each of their first steps on earth were teensy. These great beasts came from little packages, hatching out of eggs no bigger than grapefruits or soccer balls. They must have had a ridiculous growth rate, "said D. Cary Woodruff, director of paleontology at the Great Plains Dinosaur Museum in Montana.

Woodruff knows how to do these things – along with a team of dinosaur experts, Woodruff describes the smallest diplodocus skull ever found in the journal Scientific Reports. The skull, from a diplodocus the scientists Andrew nicknamed, could fit into Woodruff's cupped palms.

Sauropod skulls are rare. Immature skulls, tiny and fragile, are rare still. Paleontologists can glean lots of information from skulls: Fossilized teeth are markers of what it ate. This skull was just about nine inches long. Andrew had oversize eyes, a short muzzle and unusual teeth.

Skulls are particularly valuable to experts who study sauropod growth, too, because other developmental features are comparatively rare, Woodruff said. Dinos like triceratops had frills and horns, which scientists can track though various ages of the animals' life. Not so for a sauropod.

The newly described skull fills critical gaps in the understanding of sauropod size and development, Woodruff said. Adult diplodocuses had teeth like wooden pegs. They were grazers, like cattle, nuzzling up to soft ferns with their long snouts. Other sauropods, like camarasaurus, had spoon-shape teeth, better to munch on tougher vegetation.

Andrew, surprisingly, had both types of teeth: pegs in the front, spoons in the back. This, Woodruff predicts, would have allowed Andrew to chow down on all sorts of food, nipping at soft ferns but also crunching through more fibrous stuff.

"Said Macalester College paleontologist Kristina Curry Rogers, who was not involved with this researched baby baby sauropods from fossils found in Madagascar" It would be tough to imagine that they would like to see the same things in their lives given the size disparity as they aged. . "There is certainly no way that juvenile sauropods could feed the same browse heights as adults."

The skull and two vertebrae were collected from a quarry in Montana. Woodruff estimated to be about 2 to 4 years old, about 20 feet long and about chest-height. That's tiny, it had survived, would have grown to about 90 feet long and 13 tons in the span of two decades.

The nickname Andrew cam from industrialist Andrew Carnegie, who has been digested with fossils and has a namesake sauropod – Diplodocus carnegii. The study authors are not exactly sure what the species is, but they know it is a diplodocid, meaning a member of the same family as diplodocus. (The paleontologists have no idea whether the animal was male or female.)

Andrew was found among a jumble of other young sauropods, Woodruff said. He said that this is probably an age of segregated herd. In this view, diplodocuses were the opposite of helicopter parents. He suspects the animals were like the turtles: A mother 's pastures at laying eggs, leaving the hatchlings to fend for themselves.

The Swiss-army teeth, Woodruff said, is a sign that the young sauropods did not rely on adults to feed the ferns. "If that's the case, why do they have different kinds of teeth?" He said.

Rogers curry was not sure the teeth were so revealing. "I do not see such an obvious argument when it comes to the link between differential feeding strategies and a lack of parental care," she said. She said that hypothesis needs more data, including anatomical features beyond a skull and a few vertebrae.

An illustration of the young diplodocus "Andrew" in its environment. (Andrey Atuchin)

There's still plenty more to study. "I want to find sauropods smaller than Andrew," Woodruff said. "There's still so much more we can learn."

Even younger sauropods could shape the idea of ​​how they lived. "As adults, they are so giants that they can almost seem like biological impossibilities – it's really challenging to understand how much we're doing in an evolutionary sense," Curry Rogers said. "Sometimes, studying sauropods is like studying aliens."

The Andrews Bones Up Close Beginning Nov. 11, Woodruff said, when the skull is unveiled at the Cincinnati Museum.

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