Stegosaurus

Basic Information

Stegosaurus lived during the Late Jurassic Period, about 155 to 150 million years ago, making them one of the last dinosaurs to live before the Cretaceous Period!

Scientists gave Stegosaurus its name in 1877, and it means “roof lizard” or “covered lizard” because they initially thought its plates lay flat like roof tiles!

A full-grown Stegosaurus could reach lengths of up to 30 feet (9 meters), about as long as three school buses lined up together!

Despite its massive size, Stegosaurus had a brain about the size of a hot dog, weighing only 80 grams!

Stegosaurus belonged to a family of dinosaurs called Stegosauridae, which includes other plate-backed dinosaurs like Kentrosaurus and Tuojiangosaurus!

The first Stegosaurus fossil was discovered near Morrison, Colorado, by Professor Arthur Lakes in 1877!

A fully grown Stegosaurus could weigh up to 5 tons (4,500 kilograms), about as heavy as an elephant!

Stegosaurus was a pure herbivore, meaning it only ate plants, and its favorite foods were likely ferns, cycads, and horsetails!

Scientists estimate that Stegosaurus could only move at speeds of about 5 miles per hour (8 km/h), about as fast as you can ride a bike!

Over 80 different Stegosaurus specimens have been found in the western United States, making it one of the best-studied dinosaurs!

Physical Features

Stegosaurus had between 17 and 22 large, kite-shaped bony plates along its back, arranged in two alternating rows.

The largest plates on a Stegosaurus’s back could grow up to 2 feet (60 centimeters) tall and 2 feet wide!

Recent studies suggest that Stegosaurus plates were covered in a protective layer of keratin, the same material that makes up your fingernails!

Stegosaurus had a unique tail with four long spikes known as the “thagomizer,” each measuring up to 3 feet (90 centimeters) in length!

Scientists have found that male and female Stegosaurus might have had differently shaped plates, just like male and female peacocks have different feathers!

Stegosaurus had strong feet with three toes on the back legs and five toes on the front legs. Each toe had a sharp hoof to help it walk easily, even on soft ground!

The skin of Stegosaurus was covered in small, round, bony structures called osteoderms that provided extra protection!

Stegosaurus had a short neck and a small head, so it mostly ate plants that grew close to the ground, like ferns and bushes!

Unlike many other dinosaurs, Stegosaurus had cheeks that helped it keep food in its mouth while chewing!

The plates on a Stegosaurus’s back were not solid bone but were filled with blood vessels that could help regulate its body temperature!

Scientists believe Stegosaurus used its tail spikes, called a thagomizer, to defend itself against predators like Allosaurus!

Hunting & Defense

The tail of a Stegosaurus was very flexible and could swing side to side with enough force to pierce a predator’s skin!

Some scientists believe that Stegosaurus’s back plates may have changed color when the dinosaur was excited or scared, similar to how some lizards change color today!

Despite being a plant-eater, Stegosaurus had powerful leg muscles that could help it stand its ground against meat-eating dinosaurs!

Habitat & Environment

Stegosaurus lived in what is now western North America, in an environment that was warm and semi-arid with seasonal rainfalls!

During the time of Stegosaurus, there were no grass or flowering plants yet — they ate mostly ferns, cycads, and primitive conifers!

Stegosaurus shared its habitat with other famous dinosaurs like Apatosaurus, Diplodocus, and Allosaurus!

The world during Stegosaurus’s time was warmer than today, with no polar ice caps and higher sea levels!

Stegosaurus fossils have been found in rock layers that show they lived near ancient rivers and floodplains!

Discovery & Fossils

The most complete Stegosaurus skeleton ever found is nicknamed “Sophie” and is displayed at the Natural History Museum in London!

Scientists can tell how old a Stegosaurus was when it died by counting the growth rings in its bones, just like tree rings!

Paleontologists have found Stegosaurus footprints that help them understand how these dinosaurs walked!

Some Stegosaurus fossils show signs of injuries that healed while the dinosaur was alive, proving they could recover from wounds!

In 1885, Marshall P. Felch discovered a nearly complete Stegosaurus skeleton in Garden Park, near Cañon City, Colorado.

Daily Life

Scientists think Stegosaurus probably lived in small family groups rather than large herds!

Stegosaurus likely used low-pitched sounds and body language to communicate with each other!

Young Stegosaurus had different shaped plates than adults, and their plates grew and changed shape as they got older!

Stegosaurus probably spent most of its day eating, as it needed to consume large amounts of plants to sustain its huge body!

Scientific Understanding

Scientists use CT scans and 3D modeling to study Stegosaurus fossils and understand how their muscles and joints worked!

Recent studies of Stegosaurus teeth show they were replaced every 95 days to keep them sharp for cutting tough plants!

Scientists have found that Stegosaurus plates had different shapes in different species, helping them tell species apart!

Stegosaurus’s tail could swing side to side, and it might have been able to move it up and down a little, like a drawbridge!

Physical Adaptations

Stegosaurus had special teeth with pointed leaf-shaped crowns that were perfect for stripping leaves from plants!

The nostrils of Stegosaurus were located high on its snout, which may have helped it smell predators approaching!

Stegosaurus had bony plates (osteoderms) in its skin even on its throat area, giving it extra protection from attackers!

Scientists have discovered that Stegosaurus had powerful jaw muscles that could crush tough plant material!

The eyes of Stegosaurus faced sideways, giving it a wide field of view to watch for danger!

Growth and Development

Baby Stegosaurus were probably only about the size of a house cat when they hatched from their eggs!

Scientists think it took about 15 years for a Stegosaurus to reach its full adult size!

Young Stegosaurus had smaller, more pointed plates than adults, which grew larger and more triangle-shaped as they aged!