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Pachycephalosaurus was a dome-headed dinosaur. Its huge head housed an incredibly thick skull, a tiny brain, and large eyes. Its rounded skull was up to 10 inches thick (25 cm).
Pachycephalosaurus grew to be about 15 feet long (4.6 m) and may have weighed roughly 950 pounds (430 kg). Pachycephalosaurus probably had a good sense of smell. It had bumpy knobs on its snout and along the rear of its skull. This plant-eater had short forelimbs and a stiff tail (which had a distinctive mesh of interwoven tendons surrounding its rear portion).
Pachycephalosaurs were herding dinosaurs that lived in small groups in coastal and upland regions. Running was probably the first line of self-defense.
It had long been thought that Pachycephalosaurus' huge dome may have been used for ramming rivals during mating and dominance combat, for attracting mates, and as a last-ditch self-defense against predators (this idea was first presented by Ed Colbert in 1955). Paleontologist Mark Goodwin of the University of California at Berkeley has analyzed many pachycephalosaur skulls (including those of Pachycephalosaurus), finding no evidence of healed scars. Also, under close analysis, the thick skull bone is not rigid and solid, but porous and fragile when put under extreme pressure. ``It's time to kill the myth ... It certainly wouldn't be in their own best interests to ram heads in a fight,'' said Goodwin ``They would have killed each other, and a couple of bowling balls would hardly make good targets.'' It is more likely that Pachycephalosaurus butted other animals sides (flank-butting), rather than their heads. This would inflict damage on the other animal and not injure the Pachycephalosaurus.
WHEN PACHYCEPHALOSAURUS LIVED
Pachycephalosaurus lived during the late Cretaceous period, about 76 to 65 million years ago, toward the end of the Mesozoic, the Age of Reptiles. Among the contemporaries of Pachycephalosaurus were Albertosaurus and Troodon, Maiasaura, Tyrannosaurus rex, Ankylosaurus (an armored herbivore), Parasaurolophus, Corythosaurus (a crested dinosaur), and Dryptosaurus (a leaping dinosaur).
Pachycephalosaurs probably evolved from Hypsilophodon, a small, agile, bipedal herbivore.
Pachycephalosaurus was an herbivore, eating soft plants, fruit, and seeds. Its teeth were small and sharp.
Pachycephalosaurus walked on two legs, and was not a very fast dinosaur. When it walked or ran, it probably held its back level to the ground. It may have gone on all fours to forage for low-lying plants.
DISCOVERY OF FOSSILS
Pachycephalosaurus was discovered in 1938 by William Winkley on the family ranch outside of Ekalaka, Montana, USA. It was named Pachycephalosaurus in 1943 by Barnum Brown and Erich M. Schlaikjer. Although complete fossils are rare, many thick skull fragments have been found. Pachycephalosaurus and other pachycephalosaur fossils have been found in Alberta, Canada, the western United States, the Isle of Wight, Mongolia and Madagascar.
Pachycephalosaurus belonged to the:
- Order Ornithischia dinosaur - bird-hipped, herbivorous dinosaurs
- Suborder Pachycephalosauria - thick-skulled herbivores (possibly herding) which includes: Pachycephalosaurus, Stegoceras, Wannanosaurus, and others.
- Genus Pachycephalosaurus
- Type species - P. wyomingensis (Gilmore, 1931) (previously known as Troodon).
PACHYCEPHALOSAUR AND PACHYCEPHALOSAURUS LINKS
Pachycephalosaur Pictures from Illinois State Geological Survey
Dinosaurs and other vertebrates of the Hell Creek Formation (Upper Cretaceous) of NW South Dakota, USA
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