Sunday, July 10, 2011

Marginocephalians


Marginocephalians are a group of Ornithischian (bird-hipped) dinosaurs that have a distinctive skull structure (a slight shelf or bony frill on the back of the skull), a unique palate (part of the mouth) and a short pubis (part of the hip). These plant-eaters include the Ceratopsians (horned dinosaurs like Triceratops, Styracosaurus, Pentaceratops, Protoceratops, etc.) and the Pachycephalosaurians (thick-skulled dinosaurs like (Stegoceras, Pachycephalosaurus, etc.). Marginocephalians may have evolved from the closely-related Ornithopods.

     Protoceratops:


Protoceratops walked on four legs, had a large head, a bulky body, a parrot-like beak, cheek teeth, and a small frill on its head. Males may have had larger frills than females, indicating that the frill may have been used in courtship and mating.

Protoceratops was about 6 to 8.2 feet (1.5-2.5 m) and weighed roughly 900 pounds (400 kg). It was about 3 feet tall (to the top of the shoulders). Protoceratops lived in the late Cretaceous period, about 86 to 71 million years ago, toward the end of the Mesozoic, the Age of Reptiles. Protoceratops was possibly a herding animal, like several other ceratopsians. This hypothesis is supported by the decision of bone beds, large deposits of bones of the same species in an area, and large groups of nests. Each nest had 12 or more eggs, laid in a spiral fashion.Protoceratops was an herbivore, a plant eater. It probably ate cycads and other prehistoric plants with its tough, hook-like beak.Protoceratops walked on four short legs; it was a relatively slow dinosaur. Dinosaur speeds are estimated using their morphology (characteristics like leg length and estimated body mass) and fossilized track ways.

Styracosaurus:

Styracosaurus was a dinosaur that walked on four short legs. This large plant-eater had a six-spiked frill projecting from the back of its skull. It also had an upward-pointing horn on its nose (2 feet (60 cm) long and 6 inches (15 cm) wide), and two small horns above its eyes. These spikes and the horn probably provided protection from predators, and were possibly used in mating rituals and rivalry. It had a short, thick, pointed tail, a large, bulky body, a large skull and a beak. Styracosaurus hatched from eggs. Styracosaurus was about 18 feet (5 m) long, 6 feet (1.8 m) tall, and weighed up to 3 tons.

Styracosaurus lived in the late Cretaceous period, about 77-70 million years ago. It was among the last of the dinosaur species to evolve before the Cretaceous-Tertiary extinction 65 million years ago. Among the contemporaries of Styracosaurus were Tyrannosaurus rex, Ankylosaurus (an armored herbivore), Corythosaurus (a crested dinosaur), and Dryptosaurus (a meat-eating dinosaur). Styracosaurus may have been a herding animal, like some other ceratopsians. This hypothesis is supported by the finding of bone beds, large deposits of bones of the same species in an area. Styracosaurus hatched from eggs, and the young may have been cared for by parents.When threatened by predators, Styracosaurus may have charged into its enemy like a modern-day rhinoceros does. This would have been a very effective defense.Styracosaurus probably ate cycads, palms, and other prehistoric plants with its tough beak. It could also chew well with its cheek teeth (like other ceratopsians, but unlike most other dinosaurs).

Notoceratops:

Notoceratops was a ceratopsian (a frilled, horned, quadrupedal, herbivorous dinosaur with a beak) known only from a late Cretaceous jaw bone. Notoceratops walked on four sturdy legs, had a large head, a bulky body, a parrot-like beak, cheek teeth, and a small frill on its head.Notoceratops lived in the late-Cretaceous period, about 83-73 million years ago, toward the end of the Mesozoic, the Age of Reptiles. Notoceratops may have been a herding animal, and probably laid eggs, like other Ceratopsians. Notoceratops was an herbivore, a plant eater. It probably ate cycads and other prehistoric plants with its tough, hook-like beak.

Triceratops:

Triceratops was a rhinoceros-like dinosaur. It walked on four sturdy legs and had three horns on its face along with a large bony plate projecting from the back of its skull (a frill). One short horn above its parrot-like beak and two longer horns (over 3 feet or 1 m long) above its eyes probably provided protection from predators. The horns were possibly used in mating rivalry and rituals. It had a large skull, up to 10 feet (3 m) long, one of the largest skulls of any land animal ever discovered. Its head was nearly one-third as long as its body. Triceratops hatched from eggs.Triceratops was about 30 feet long (9 m), 10 feet tall (3 m), and weighed up to 6-12 tons.Triceratops lived in the late Cretaceous period, about 72 to 65 million years ago, toward the end of the Mesozoic, the Age of Reptiles. It was among the last of the dinosaur species to evolve before the Cretaceous-Tertiary extinction 65 million years ago.

Montanoceratops:

Montanoceratops walked on four legs, had a large head, a bulky body, a parrot-like beak, a small nose horn, cheek teeth, and a small frill on its head. Males may have had larger frills than females, indicating that the frill may have been used in courtship and mating.Montanoceratops was up to 6 feet long (1.8 m) and weighed about 900 pounds (400 kg). Montanoceratops lived in the late-Cretaceous period, about 72 to 65 million years ago, toward the end of the Mesozoic, the Age of Reptiles.Montanoceratops was an herbivore, a plant eater. It probably ate cycads and other prehistoric plants with its tough, hook-like beak.
Monoclonius:

Monoclonius was a large, early ceratopsian with a huge head that was held close to the ground. Its skull was 6 feet (1.8) long from beak to frill. It had a small frill on its head with a single nose horn that pointed upwards and two smaller horns over the eyes. The short snout ended in a parrot-like, toothless beak, but Monoclonius also had many cheek teeth. It walked on four legs with hoofed toes, had a bulky body, and a short, thick, pointed tail.Monoclonius was up to 16.5 feet (5 m) long and may have weighed about 4780 pounds (2170 kg). Monoclonius lived in the late Cretaceous period, about 76 to 73 million years ago, toward the end of the Mesozoic, the Age of Reptiles. Monoclonius may have been a herding animal, since some other ceratopsians may have been. Monoclonius was an herbivore, a plant eater. It probably ate cycads, palms, and other prehistoric plants with its tough, hook-like beak. It could also chew well with its cheek teeth (like other Ceratopsians, but unlike most other dinosaurs).

Pachycephalosaurus:

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 animal’s sides (flank-butting), rather than their heads. This would inflict damage on the other animal and not injure the Pachycephalosaurus.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.

Stegoceras:

Stegoceras was a small, plant-eating dinosaur that had a large, thick-skulled head. This dinosaur may have butted heads with others of its kind in bone-shaking contests.Stegoceras was a dome-headed, bipedal dinosaur. Its large head housed a thick skull, a relatively large brain, and large eyes. Its skull was about 3-4 inches (8 cm) thick. Males had thicker domes than females, and older Stegoceras had thicker domes than younger ones. Stegoceras had a fringe of horny knobs along the rear of its skull. It had short forelimbs and a large, stiff tail.Stegoceras grew to be about 7 feet long (2.1 m) and 4 feet tall (1.2 m). This plant-eater weighed roughly 170 pounds (78 kg). Stegoceras was a herding dinosaur that lived in small groups in coastal and upland regions. Running was probably its first line of defense.It had long been thought that Stegoceras' (and other pachycephalosaurs') thick dome may have been used for ramming rivals during mating and dominance combat, for attracting mates, and as a last-ditch defense against predators. 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.'' Stegoceras was an herbivore (a plant-eater, a primary consumer). It had small, curved teeth with serrated edges, a relatively large brain, and large eyes.Stegoceras lived during the late Cretaceous period, toward the end of the Mesozoic Era, the Age of Reptiles, about 76-65 million years ago. Among the contemporaries of Stegoceras were Albertosaurus and Maiasaura, Tyrannosaurus rex, Ankylosaurus (an armored herbivore), Parasaurolophus, Corythosaurus (a crested dinosaur), and Dryptosaurus (a meat-eating dinosaur).

Wannanosaurus:

   Wannanosaurus (named after the Chinese province where its very incomplete skeleton was found) was a tiny homalocephalid dinosaur about 2 feet (60 cm) long. It was a very primitive Pachycephalosaur (related to Pachycephalosaurus and Stegoceras, other dinosaurs with thick skulls that probably engaged in head-butting activities). The homalocephalids had thick, but flat-topped skulls. It was an herbivore that walked on two strong legs, had short arms, a stiff tail, and a thick-set body.Wannanosaurus may have been a herding dinosaur that lived in small groups in coastal and upland regions. Running was probably the first line of self-defense. Wannanosaurus' thick skull may have been used for ramming rivals during mating and dominance combat, for attracting mates, and as a last-ditch self-defense against predators.Wannanosaurus was an Ornithischian dinosaur, the order of bird-hipped, herbivorous dinosaurs. It was a member of the group Marginocephalia, and was the largest and last member of the group Pachycephalosauria (herding, thick-skulled herbivores which includes Stegoceras, Pachycephalosaurus, Wannanosaurus, and others) and the family Homalocephalidae (with thick, flat-topped skulls). Wannanosaurus may be the most primitive pachycephalosaur.Wannanosaurus lived during the late Cretaceous period, about 83 to 73 million years ago.Wannanosaurus was an herbivore, eating soft plants, fruit, and seeds. Its teeth were small and sharp.

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