Know Your Sauropod
by AMNH on
But more astounding is this: these strange giants rank among Earth’s great success stories, roaming the planet for 140 million years. Fossil specimens of these extinct herbivores have been found on every continent. Here’s an introduction to a few stupendous species, including several of the largest animals to ever walk the planet.
Apatosaurus may be one of the best-known sauropod species, though it’s just as likely you first heard about this late Jurassic giant under another name: Brontosaurus.
Why the two names? While examining sauropod fossils in the late 19th century, Yale paleontologist O.C. Marsh used two different terms to describe what he believed to be the remains of two different sauropods. Years later, it was discovered that both fossils belonged to the same species. The name Apatosaurus had appeared in scientific publications first, so it became the official designation—though Brontosaurus managed to stick, too.
In life, this gargantuan animal weighed about 26 tons (24,000 kg) and measured about 76 feet (21 m) long—and it maintained its mind-boggling bulk on a diet of plants alone. Like other sauropods, Apatosaurus had quite a small head—and small brain, too. (As a rule, relative brain size is related to diet, and plant eaters get by with smaller brains than meat-eaters: after all, their food doesn’t try to escape!) An adult Apatosaurus brain weighed 4 ounces (125 g), whereas an adult human brain tips the scales at 48 ounces (1,400 g).
Brains aren’t the only small sauropod features. Compared to their large owners, fossil sauropod teeth can seem puny—including those of Diplodocus. This 13-ton (12,000 kg) herbivore presumably used its pencil-shaped teeth for nipping or stripping leaves or needles from trees.
This sauropod species also happens to have a particularly long history at the Museum. A Diplodocus fossil was the first dinosaur fossil ever excavated by Museum paleontologists, in 1897, at Como Bluff, Wyoming. A femur from this specimen is currently on view in the Museum’s Sauropods at the Museum exhibit in the Wallach Orientation Center, across from another notable sauropod, The Titanosaur.
Long necks were key to sauropod gigantism. The position of sauropod necks continues to be debated by scientists. In some reconstructions, the animals’ necks are giraffe-like and straight; in others, they’re horizontal. Many experts think that neck pose may have varied by species. Such differences make sense, because they mirror the diverse habitats, with plants of different heights, that sauropods occupied.
With its long forelegs, Brachiosaurus likely kept its neck in an upright position while it fed on tall trees. But its neck was flexible enough to move in a wide arc—though very slowly!—giving the animal access to a lot of food.
This medium-sized sauropod lived in western North America about 155 million years ago. The cavities and hollows in fossils of its neck vertebra were so striking to scientists that they named the animal Camarasaurus, which means “chambered reptile.” These hollows likely held air-filled sacs, lightening sauropod necks by more than 50 percent—making the holding and moving of those long necks possible.
In the 1990s, a nearly complete skeleton of a Camarasaurus was discovered at Howe Quarry in Wyoming, close to a 1934 dig site where an expedition from the American Museum of Natural History discovered about 4,000 dinosaur fossils. Howe Quarry remains one of the world’s most densely packed fossil sites for sauropod bones. (To go behind the scenes with paleontologists on an ongoing project to identify specimens from the 1934 Howe Quarry dig, join the Museum’s Dino Detectives group on Facebook.)
Many of the biggest sauropods are members of a group called titanosaurs. At 122 feet (37 m) long and weighing an estimated 70 tons—or the equivalent of 10 African elephants—the sauropod species Patagotitan mayorum is one of the largest dinosaurs ever discovered. The species is so new that when The Titanosaur first went on view at the Museum in 2016, it hadn’t been given its scientific name—so the exhibit was named for the gargantuan group instead.
Patagotitan mayorum lived during the late Cretaceous period in what is today Argentina’s Patagonia region, where some of the largest titanosaurs have been found. The Museum’s skeleton is a cast—real fossils would be far too heavy to mount for display— that includes exact replicas of 84 Patagotitan mayorum bones as well as others that have been modeled on close relatives.
Just how large were these sauropods? So large that the adults probably had nothing to fear from even the biggest carnivores. Dead animals were a different story—the site where the Museum’s titanosaur was found also yielded 80 teeth of a large, two-legged meat-eater.