Cleveland Museum of Natural History

Steggie – Stegosaurus ungulatus

"Steggie," the sculpture of a Stegosaurus that sits outside the main entrance to The Cleveland Museum of Natural History, has greeted visitors and served as a play structure for generations of children. The 18-foot-long, 8-foot-tall Stegosaurus in place today is the second sculpture to sit outside the museum since 1968. After nearly 30 years, the original Steggie, a copy of the Stegosaurus created by New York sculptor Paul Jonas for the New York World's Fair in 1964-65, became too weathered and worn. In 1997, the Museum commissioned an identical copy from the original casts at Louis Jonas Studio in Hudson, New York. Meanwhile, the previous sculpture was refurbished and found a second life at the Berkshire Museum in Pittsfield, Massachusetts, where it is called "Wally" in honor of its walnut-sized brain.

 

The Art and Science of the Stegosaurus

The Stegosaurus lived in the Late Jurassic Period, from 156 million to 145 million years ago. It was an herbivore (plant-eating) dinosaur, whose genus name means "roofed reptile"—its "roof" being two rows of spiky, thin bone plates called osteoderms that stand vertically along its neck, back and tail. It is one of the world's most widely recognized dinosaurs, owing partly to its striking appearance and its discovery early in the history of dinosaur hunting. Stegosaurus armatus, the first species found, was unearthed in 1877 by Othniel Charles Marsh, Yale University, in Colorado's Morrison Formation.

An Artful Arrangement

The most distinctive feature of Stegosaurus is the arrangement of plates along its back, which vary in size and appearance. There are several theories how these plates were arranged. Paleontologists first thought they were positioned flat on the animal’s back, hence the name "roofed reptile," but it has since been established that they stood vertically at various angles.

There has been speculation among scientists about the function of the plates. They are widely thought to be a type of armor or protection to deter predators. The surfaces of the plates show evidence of being crossed with blood vessels and covered with skin. Some paleontologists have speculated the plates helped to control the animal's body temperature, cooling the animal by helping to dissipate heat. Conversely, like solar panels, they may have absorbed heat from the sun. Other paleontologists point to identification as the primary reason for the plates; they may have helped Stegosauruses recognize one another or select a mate.

In addition to the animal's broad plates, at the end of Steggie's tail are four long spikes, or spines. It is widely thought that these spikes functioned as weapons, powered by tail muscles that enabled Stegosaurus to swing its tail at predators. The tail spikes varied in size according to the individual animal, and one species of Stegosaurus, S. longispinus, had very long spikes.

Stegosaurus is known its walnut-sized brain, estimated to weigh only 70 grams (2.5 ounces). However, most plant-eating dinosaurs had small brains relative to their body size when compared to modern herbivores. A modern elephant's brain is 50 times this size, yet the elephant is smaller than Stegosaurus.

A Model Dinosaur

Stegosaurus had front legs that were much shorter than its hind legs, as a result it could not have raised itself up on its hindlimbs for more than a limited time. If Steggie was to be recast today, one feature would be dramatically different: Steggie would hold his tail aloft. According to some recent thinking in Vertebrate Paleontology, some experts suggest the muscles in the Stegosaurus' tail were more powerful than originally assumed

No visit to the Museum is complete without a moment with Steggie, the Museum's perennial outdoor ambassador and celebrated representative of his kind. The sculpture is an icon in the Museum's permanent collection and a tactile complement to the fossil specimens on display inside the building.