Stegosaurus ungulatus

Overview

Stegosaurus ungulatus is a distinct species of the famous plated dinosaur that lived during the Late Jurassic period, approximately 155 to 150 million years ago in what is now North America. While closely related to S. stenops, this species had its own unique features that set it apart.

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Taxonomy & Classification

• Clade: Ornithischia
• Family: Stegosauridae
• Diet: Herbivorous
• Species Type: One of several Stegosaurus species

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Physical Characteristics

Size & Build

• Length: About 9 meters (30 feet)
• Weight: 3,100-3,800 kg (3.4-4.2 tons)
• Height: Up to 4 meters at the plates

What Makes It Different?

S. ungulatus stands out from S. stenops in several ways:

• Longer hind limbs compared to front legs
• Smaller, more pointed plates with wide bases and narrow tips
• Additional small, flat spine-like plates near the thagomizer (tail spikes)
• Overall more elongated appearance

The Distinctive Plates

• Plates were more pointed and triangular
• Arranged in the characteristic two rows along the back
• Wider at the base, tapering to sharper points
• The unique plate shape helps scientists identify this species

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The Thagomizer

Tail Defense

Like all Stegosaurus, S. ungulatus had:

• Four sharp tail spikes for defense
• Additional small, flat spines just before the main spikes
• A powerful tail that could swing with devastating force
• This extra armor made its tail even more formidable!

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Discovery & History

Early Finds

• One of the original species described by O.C. Marsh in 1879
• Found in the Morrison Formation of the western United States
• Part of the famous "Bone Wars" dinosaur discoveries
• Fossils found in Colorado, Wyoming, and Utah

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Lifestyle & Habitat

Jurassic World

S. ungulatus shared its environment with:

• Giant sauropods like Diplodocus and Brachiosaurus
• Predators like Allosaurus and Ceratosaurus
• Other plant-eaters like Camptosaurus

Diet

• Fed on low-growing plants
• Used its beak to crop vegetation
• Lived in floodplains and forests
• Probably moved in herds for protection

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Stegosaurus Species Comparison

Feature	S. ungulatus	S. stenops
Hind Limbs	Longer	Standard
Plate Shape	Pointed, narrow tips	Broad, kite-shaped
Extra Tail Plates	Yes	No
Body Shape	More elongated	More compact

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Cool Facts

• The name "ungulatus" means "hoofed"—referring to its feet
• Scientists once thought different Stegosaurus species were different growth stages
• The extra tail plates might have made its defense even more effective
• Both male and female probably had similar plates and spikes
• Like other Stegosaurus, it had a brain the size of a walnut!

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Stegosaurus ungulatus shows us that even within a single dinosaur genus, evolution created wonderful variety—each species perfectly adapted to its environment!