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Stegosaurus Facts & Worksheets

The Stegosaurus is a genus of plant-eating, four-legged, armored dinosaurs from the Late Jurassic Period, distinguished by kite-shaped vertical plates along their backs and tail spikes.

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Stegosaurus is a genus of plant-eating, four-legged, armored dinosaurs from the Late Jurassic Period, distinguished by kite-shaped vertical plates along their backs and tail spikes. The genus’ fossils have been discovered in the western United States and Portugal, where they were found in Kimmeridgian- to early Tithonian-aged strata dated between 155 and 145 million years ago.

See the fact file below for more information on the Stegosaurus or alternatively, you can download our 27-page Stegosaurus worksheet pack to utilize within the classroom or home environment.

Key Facts & Information

History and Naming

Bone Wars and Stegosaurus armatus

  • Stegosaurus, one of the numerous dinosaurs reported in “Bone Wars,” was discovered by Arthur Lakes and comprised several caudal vertebrae, a dermal plate, and many more postcranial pieces found north of Morrison, Colorado, in Lakes’ YPM Quarry 5.
  • When Yale paleoanthropologist Othniel Charles Marsh reported the first fragmentary bones (YPM 1850), they became the holotype of Stegosaurus armatus.
  • Though some more complete specimens have been assigned to Stegosaurus armatus, processing of the bones and study have revealed that this sort of specimen is genuinely questionable, which is not suitable for the type species of a renowned genus like Stegosaurus.
  • As a result, the International Code of Zoological Nomenclature chose to change a well-known genus’ type species, such as Stegosaurus stenops. Marsh also referred to some S. armatus fossils wrongly. armatus includes the dentary and teeth of the sauropod Diplodocus, sauropod limb bones, and an Allosaurus tibia.
  • Many subsequent studies regarded Hypsirhophus as a synonym for Stegosaurus. However, Peter Galton (2010) proposed that it differs based on vertebral characteristics.
  • In August of the same year, Arthur Lakes discovered many massive Stegosaurus fossils in Como Bluff in Albany County, Wyoming, starting to the Upper Jurassic of the Morrison Formation.
  • He identified a third species, Stegosaurus “affinis,” in 1881 based only on a hip bone, however, the specimen has since been destroyed, and the species has been deemed nomen nudum.
  • Marsh reported two new Stegosaurus species from Como Bluff in 1887, Stegosaurus duplex (YPM 1858) based on an incomplete vertebral column, partial pelvis, and partial left hindlimb from Reed’s Quarry 11, albeit the species is generally considered synonymous with Stegosaurus ungulatus.
  • The finding of a nearly complete, extended skeleton of a subadult Stegosaurus in 1885 contained previously unknown characteristics such as an entire skull, throat ossicles, and articulated plates.
  • Between 1885 and 1886, Marshall P. Felch acquired the bones; the skeleton was skilfully excavated by Felch, who first split the structure into substantial chunks and prepared them separately. That year, Marsh received the frame in 1887 and called it Stegosaurus stenops, or narrow-faced roof lizard.
  • The highly complete and articulated type specimen of Stegosaurus stenops, albeit not yet entirely prepared, allowed Marsh to produce the first effort at a rebuilt Stegosaurus skeleton.

Early Skeletal Mounts and Plate Interpretation

  • The S. stenops skeleton since then, stenops has been on display in Washington, D.C.’s National Museum of Natural History, where it has resided since 1915. Created another mount for the NMNH in building a composite skeleton of various specimens known as S. stenops USNM 6531 is a complete collection of stenops from Quarry 13 at Como Bluff in 1887.
  • In 1910, at the Peabody Museum of Natural History, the S. ungulatus type specimen Richard Swann Lull included ungulatus (YPM 1853) into the first ever exhibited frame of a stegosaur. It was initially mounted with paired plates positioned wide over the ribs but was remounted in 1924 with two spaced rows of scales along the back’s midline.
  • S. marshi was the following Stegosaurus species to be named. Frederick Lucas created marshi in 1901. Later, he placed this species in the new genus Hoplitosaurus. Lucas also revisited the Stegosaurus’s life look, determining that the plates were positioned in pairs in two rows above the rib bases.
  • Charles Gilmore objected to Lull’s view in 1914, pointing out some specimens of S. stenops. The plates of stenops, including the now-completely prepared holotype, were preserved in alternating rows towards the top of the back, with no signs of the plates shifting relative to the body during fossilization. The interpretation of Gilmore and Lucas became the widely acknowledged standard and modified Lull’s mount at the Peabody Museum to reflect this in 1924.

Plate Arrangement

  • Plate arrangement is a crucial topic in books and articles on Stegosaurus, and the debate was pivotal in the history of dinosaur restoration. Over the years, four different plate configurations have been presented.
  • The plates form shingle-like armor down the back. Marsh’s first interpretation resulted in the name “roof lizard.” As they discovered more full plates, their shape revealed that they stood on the edge rather than resting flat.
  • Marsh released a more recognisable image of Stegosaurus in 1891, with a single row of plates. It was abandoned quite early (seemingly because it was poorly apprehended how the plates were entrenched in the skin, and they were deemed to coincide too much in this arrangement). Stephen Czerkas recreated it in the 1980s, in a somewhat modified form, based on the structure of dorsal iguana spines.
  • As in Knight’s 1901 rebuilding and the 1933 film King Kong, the plates were coupled in a double row along the rear.
  • By the early 1960s, this was a widely held belief, owing mainly to S stenops. This configuration may be seen in stenops fossils where the plates are still partly articulated. Because this arrangement is chiral, a specimen must be separated from its unique mirror-image form.

Second Dinosaur Rush

  • Following the end of the Bone Wars, the Marsh and Cope encouraged several prominent institutions in the eastern United States to build their dinosaur fossil collections.
  • Near 1897, the American Museum of Natural History led the first expedition, discovering many scattered but fragmentary Stegosaurus fossils in Bone Cabin Quarry in Como Bluff. 
  • These bones have not been characterized and were mounted in 1932, the mount being a combination of AMNH 650 and 470 specimens from Bone Cabin Quarry. The AMNH mount has been cast and is now on display at the Field Museum, which did not acquire any Stegosaurus skeletons during the Second Dinosaur Rush.
  • The complete skeleton discovered in the quarry, CM 11341, was utilized as the foundation for a composite Stegosaurus mount in 1940, along with numerous other specimens to complete the support. Carnegie workers also discovered a skull (CM 12000), one of the few known. Both the AMNH and CM specimens have been dubbed Stegosaurus ungulatus.

Description

  • Because of the characteristic double row of kite-shaped plates ascending vertically along the curved back and the two pairs of long spikes expanding horizontally at the end of the tail, the quadrupedal Stegosaurus is one of the most clearly identified dinosaur genera.
  • S. stenops measured 6.5 m (21.3 ft) in length and weighed 3.5 metric tons (3.9 short tons), whereas S. ungulatus grew to be 7 m (23.0 ft) long and weighed 3.8 metric tons (4.2 short tons).
  • Most of what we know about Stegosaurus comes from the bones of older animals; nevertheless, young Stegosaurus remains have recently been discovered. One subadult specimen unearthed in Wyoming in 1994 measures 4.6 (15.1 ft) long and 2 m (6.6 ft) high, weighing 1.5-2.2 metric tons (1.6-2.4 short tons) while living. It may be seen at the University of Wyoming Geological Museum.

Skull

  • The long and thin skull was modest compared to the rest of the body. It possessed a tiny antorbital fenestra, a hole between the nose and eye found in most archosaurs, including contemporary birds, but absent in present crocodylians.
  • The low location of the skull shows that Stegosaurus was a browser of low-growing plants. The lack of front teeth and their likely substitution by a horn beak or rhamphotheca corroborate this theory.
  • Such a large beak was most likely unique to Stegosaurus and a few other sophisticated stegosaurids among ornithischians, which typically possessed beaks limited to the jaw points. Stegosaurian teeth were tiny, triangular, and flat, with worn facets indicating that they ground their food. The actual brain structure of Stegosaurus is unknown. However, the brain was tiny for a dinosaur.

Skeleton

  • There are 27 bones in the vertical column before the sacrum, a varied number of vertebrae in the lower spine, with four in most subadults and roughly 46 caudal (tail) vertebrae in Stegosaurus stenops.
  • The presacral vertebrae are split into cervical (neck) and dorsal (back) vertebrae, with approximately ten cervicals and 17 dorsals, resulting in a total number of one greater than Hesperosaurus and two greater than Huayangosaurus. However, Miragaia preserves 17 cervicals and an unknown number of dorsals.
  • The sacrum construction of stenops comprises four sacral vertebrae, but one dorsal is also included. In some S. stenops specimens, A caudal stenops is likewise integrated as a caudosacral. S. stenops retains 46 caudal vertebrae and up to 49; as the series progresses, the centers and the neural spines shrink until the neural spines vanish at caudal 35. The neural spines split or separate towards the top, about the middle of the tail.
  • Pads behind the toes supported all four limbs. The forelimbs were significantly shorter than the stocky hind limbs, resulting in an odd stance. The tail appears to have been kept considerably clear of the ground, but the head of Stegosaurus was likely no more than 1 m (3.3 ft) above the ground.

Plates

  • Stegosaurus is well known for its dermal plates, consisting of 17 to 22 distinct plates with flat spines. These heavily modified osteoderms (bony-cored scales) were comparable to those found in modern crocodiles and many reptiles.
  • They did not grow directly from the animal’s bones but from the skin. The most extensive plates were discovered above the hips and might be 60 cm (24 in) broad and 60 cm (24 in) tall.
  • Many plates are chiral, and no two plates of identical size and form have been discovered for an individual; yet, plates have been proven to be associated between people.
  • Hesperosaurus plate integumentary impressions display a smooth surface with long, parallel, shallow grooves. It shows that the plates had keratinous sheaths.

Classification and Species

  • The bony plates and spines of stegosaurians originated from the low-keeled osteoderms of primitive thyreophorans, just like the spikes and shields of ankylosaurs.
  • Stegosaurus is typically found in the clade Stegosauridae, which also includes the genera Wuerhosaurus and Loricatosaurus; however, Hesperosaurus is occasionally seen in the group. Raven and Maidment presented a new phylogenetic study in 2017 that had practically every known stegosaurian genus.
  • Many of the first described species are now considered legitimate or synonymous with previously recognized species, leaving just two well-known and one poorly-known species.
  • Stegosaurus fossils have been confirmed in Morrison Formation stratigraphic zone 2-6, with extra remains from the stratigraphic zone probably referring to Stegosaurus.

Paleobiology

Posture and Movement

  • Because of its small forelimbs, Marsh assumed Stegosaurus was bipedal soon after its discovery. Although Stegosaurus is undeniably quadrupedal, there has been considerable debate over whether it might have reared up on its hind legs, utilizing its tail to compose a tripod with its hind limbs to forage for higher plants.
  • Because the plates would have impeded copulation, the female stegosaur may have lain on her side while the male entered her from above and behind. Another idea is for the female to stand on all fours but stoop down the forelimbs and elevate the tail up and out of the course of the male, who is supporting his forelimbs on his lips. However, their reproductive organs could not have touched since male dinosaurs lack muscular attachments for a movable penis or a baculum.

Plate Function

  • The purpose of Stegosaurus plates has long been questioned. Marsh proposed that they served as armor, but Davitashvill (1961) disagreed, arguing that they were too flimsy and ill-placed for defensive functions, leaving the animal’s flanks exposed.
  • The plates’ circulatory system may have had a role in the danger, as Stegosaurus may have pumped blood into them, causing them to “blush” and emit a bright red warning.
  • Plates on stegosaurs, according to some, were employed to help people recognize members of their species. The employment of exaggerated features in dinosaurs to identify species has been called into doubt, given no such function exists in current species.

Thagomizer (Tail Spikes)

  • More recently, McWhinney’s analysis of the tail spikes, which revealed severe trauma-related damage, adds weight to the argument that the spikes were utilized in fighting. 
  • This study discovered that 9.8% of the Stegosaurus specimens studied had tail spike injuries. The pierced tail vertebra of an Allosaurus, into which a tail spike fits precisely, provided more evidence for this theory.
  • Each S. stenops dermal spike was around 60-90 cm (2.0-3.0 ft) long. Discoveries of articulated stegosaur armor demonstrate that these spikes protruded horizontally from the tail rather than vertically as is commonly pictured. Marsh first described S. ungulatus has eight spikes on its tail, whereas S. stenops. Recent studies, however, re-examined this and determined that this species also had four.

Second Brain

  • Stegosaurs were once thought to have a “second brain” in their hips. Marsh discovered a massive channel in the hip area of the spinal cord soon after discovering Stegosaurus, which might have held a structure up to 20 times larger than the notoriously tiny brain.
  • It has led to the widely held belief that dinosaurs such as Stegosaurus possessed a “second brain” in the tail responsible for coordinating responses in the back of the body. This “brain” was thought to have boosted a Stegosaurus when predators threatened it.

Growth and Metabolism

  • Stegosaurus juveniles have been preserved, demonstrating the genus’ growth. The two youngsters are relatively small, with the smaller one being 1.5 m (4.9 ft) and the longer one measuring 2.6 m. (8.5 ft).
  • The specimens are classified as immature because the scapula, coracoid, and lower hind limbs have not fused. Furthermore, the pelvic area of the fossils resembles Kentrosaurus juveniles.
  • Wiemann and colleagues’ 2022 analysis of numerous dinosaur taxa, including Stegosaurus, reveals that it possessed an ectothermic (cold-blooded) or giganthothermic metabolism similar to current reptiles.
  • They hypothesized that similar metabolisms were typical among ornithischian dinosaurs in general, with the group developing toward ectothermy from an endothermic (warm-blooded) predecessor.

Diet

  • Stegosaurus and its relatives were herbivores. However, their teeth and jaws are substantially different from those of other herbivorous ornithischian dinosaurs, implying a distinct eating strategy yet unknown.
  • The stegosurians were regionally widespread in the late Jurassic. Paleontologists think it ate mosses, ferns, horsetails, cycads, conifers, and fruits.
  • If Stegosaurus could have elevated itself on two legs, as Bakker suggests, it might have grazed on foliage and fruits relatively high up, with adults foraging up to 6 m (20 ft) above the ground.

Stegosaurus Worksheets

This is a fantastic bundle that includes everything you need to know about the Stegosaurus across 27 in-depth pages. These are ready-to-use Stegosaurus worksheets that are perfect for teaching students about Stegosaurus, which is a genus of plant-eating, four-legged, armored dinosaurs from the Late Jurassic Period, distinguished by kite-shaped vertical plates along their backs and tail spikes.

Complete List of Included Worksheets

  • Stegosaurus Facts
  • Taxonomic Details
  • Let’s Get Physical!
  • Thagomizer Weapon
  • Crossword
  • Amazing Dino
  • Jurassic Film
  • Word Seek
  • Plated Lizard’s Info
  • Fill in the Facts
  • Meet The Stegosaurus

Frequently Asked Questions

What is a Stegosaurus?

Stegosaurus is a genus of plant-eating, four-legged, armored dinosaurs from the Late Jurassic Period, distinguished by kite-shaped vertical plates along their backs and tail spikes.

How does Stegosaurus discover?

Stegosaurus, one of the numerous dinosaurs reported in “Bone Wars,” was discovered by Arthur Lakes and comprised several caudal vertebrae, a dermal plate, and many more postcranial pieces found north of Morrison, Colorado, in Lakes’ YPM Quarry 5.

How can we describe Stegosaurus?

Because of the characteristic double row of kite-shaped plates ascending vertically along the curved back and the two pairs of long spikes expanding horizontally at the end of the tail, the quadrupedal Stegosaurus is one of the most clearly identified dinosaur genera.

What is the function of the plates of Stegosaurus?

The purpose of Stegosaurus plates has long been questioned. Marsh proposed that they served as armor, but Davitashvill (1961) disagreed, arguing that they were too flimsy and ill-placed for defensive functions, leaving the animal’s flanks exposed.

What is the function of the second brain of Stegosaurus?

It has led to the widely held belief that dinosaurs such as Stegosaurus possessed a “second brain” in the tail responsible for coordinating responses in the back of the body. This “brain” was thought to have boosted a Stegosaurus when predators threatened it.

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