Pachycephalosaurus grangeri

Pachycephalosaurus grangeri

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Period

Cretaceous

Location

western North America

Length

4.5 meters

Weight

370–450

Diet

Omnivore

Category

Dinosaurs - Pachycephalosaurs

Family

Pachycephalosauridae

About Pachycephalosaurus grangeri

Pachycephalosaurus wyomingensis

Overview

Pachycephalosaurus, meaning "thick-headed lizard," was the ultimate bonehead dinosaur—and we mean that as a compliment! Living during the Late Cretaceous period, about 70-66 million years ago, this dinosaur had a skull roof up to 25 centimeters (10 inches) thick, making it one of the strangest-looking dinosaurs ever!

Taxonomy & Classification

  • Clade: Marginocephalia
  • Family: Pachycephalosauridae
  • Diet: Omnivorous (probably)
  • Locomotion: Bipedal

Pachycephalosaurus was the largest of the dome-headed dinosaurs!

Physical Characteristics

Size & Build

  • Length: About 4.5 meters (15 feet)
  • Weight: 370-450 kg (815-990 lbs)
  • Height: About 1.8 meters (6 feet)
  • Build: Bipedal with strong legs

That Amazing Skull!

  • Dome-shaped skull made of solid bone
  • Up to 25 cm (10 inches) thick!
  • Surrounded by bony knobs and spikes
  • Small horns pointed backward
  • Made the head look like a motorcycle helmet!

The Head-Butting Debate

Did They Ram Each Other?

Evidence FOR head-butting:

  • Thick skull perfect for absorbing impacts
  • Similar to bighorn sheep and musk oxen today
  • Would explain the elaborate dome

Evidence AGAINST:

  • Skull shape might not align properly for head-on hits
  • May have been for flank-butting instead
  • Dome might be primarily for display

The truth? Probably both display AND some combat!

Possible Skull Uses

Use How It Worked
Display Bigger dome = more impressive mate
Head-butting Like rams fighting
Flank-butting Hitting rivals in the sides
Species ID Recognizing other Pachys
Defense Ramming predators

Feeding & Diet

Probably Omnivorous

Pachycephalosaurus likely ate:

  • Leaves, ferns, and other plants
  • Seeds and fruits
  • Possibly insects and small animals
  • Small, serrated teeth suggest varied diet
  • Different from pure herbivores

Feeding Style

  • Bipedal stance let it reach different heights
  • Good eyesight for finding food
  • Quick on its feet to catch small prey?

Stygimoloch and Dracorex Mystery

Same Dinosaur, Different Ages?

Scientists now think:

  • Stygimoloch = teenage Pachycephalosaurus
  • Dracorex = juvenile Pachycephalosaurus
  • The dome grew and changed with age!
  • Young had spiky heads, adults had smooth domes
  • One of paleontology's biggest plot twists!
Name What It Really Is
Dracorex Young Pachy
Stygimoloch Teen Pachy
Pachycephalosaurus Adult

Living with T. rex

End of the Dinosaur Era

Pachycephalosaurus lived alongside:

  • Tyrannosaurus rex (main predator)
  • Triceratops (fellow herbivore)
  • Ankylosaurus (armored dinosaur)
  • Edmontosaurus (duck-billed dinosaur)
  • Just before the asteroid impact!

Discovery & Fossils

Hard to Find Complete

  • First described in 1943
  • Found in Montana, Wyoming, South Dakota
  • Part of the Hell Creek Formation
  • Complete skulls are rare
  • Body fossils even rarer—mostly just heads!

Cool Facts

  • The skull dome was made of solid bone—no air spaces!
  • Scientists think the dome may have been brightly colored
  • Lived right up until the asteroid extinction
  • May have been able to run faster than a human
  • Three "different dinosaurs" (Pachy, Stygimoloch, Dracorex) are probably one species!
  • Appeared in Jurassic World escaping its cage
  • Nickname: the "bonehead" dinosaur
  • Had remarkably good eyesight

Pachycephalosaurus was nature's headbanger—a dinosaur with the thickest skull of any land animal ever, whether it used that dome for fighting, showing off, or both!