Ceratopsians and Pachycephalosaurs
Around 144 million years ago, began the emergence of the Ornithischian dinosaurs during the cretaceous period and diversified into North America and Asia.
Ornithischians were classified as having a hip structure similar to that of birds, although they are not the descendants of birds. Marginocephalians, meaning "fringed heads" are a group of Ornithischians that have a distinctive skull structure, consisting of a slight shelf or bony frill on the back of the skull, a unique palate, and a short hip structure. These herbivores include two major groups: the Ceratopsians and the Pachcephalosaurians.
These plant-eaters include the Ceratopsians, horned dinosaurs such as the Triceratops, Styrachosaurus, Pentaceratops, and the Protoceratops. Pachycephalosaurians, thick-skulled dinosaurs like such as the Stegoceras and the Pachycephalosaurus. (1)
Ceratopsians and Pachycephalosaurs are closely related in their characteristics. Ceratopsians processed a saddle-shaped boney frill that extended from the skull to the neck and typically had horns over the nose and eyes. The most popular was the triceratops, which could reach over 26 feet and weigh in excess of twelve metric tons. Their frills served as two major functions. It protected the vulnerable neck from being harmed. The second major function that the frill provided was due to the fact that the frill contained a network of blood vessels on its underside, which were used as a means to get rid of excess heat. The Pachycephalosaurs were considered to be bipedal. They were also found to have thick skulls, flattened bodies, and tail that were covered in an array of body rods. Pachycephalosaurs were thought to have been more than fifteen feet long and processed a skull that was surrounded by a rounded dome of solid bone. It was thought that they used their heads in combat or mating contests, but that was disproved fairly recently, which I will discuss later in the paper. Both Ceratopsians and Pachycephalosaurs were “bird-hipped” and both of these suborders contained a backwards pubic bone. Both were Marginocephilia, or “fringed heads”, which is one of three clads under the Orinthiscia order. They were also herbivore dinosaurs that inherited their fringe at the back of the skull from earlier ancestors.(2) Their classi...
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...silophodon, a small, agile bipedal herbivore. The Ceratopsians appeared at beginning of cretaceous period from the family Ornithopoda. Pachycephalosaurs contained a ten inch thick skull, which was actually fairly fragile, and their first line of self defense would be to run away. Ceratopsians, which mean horned face, are large beasts with horns that can defend themselves pretty well. Both were very similar, but contained distinct differences.
Works Cited
1) Carroll, R. L. 1988. Vertebrate Paleontology and Evolution. W. H. Freeman and Company, New York.
2) http://www.trueauthority.com/dinosaurs/about.htm
3) Dr. Robert Riesz, University of Toronto, “Ceratopsia and Ornithopoda” http://www.erin.utoronto.ca/~w3bio356/lectures/ceratopsia_and_ornithopoda.html 4) Enchanted Learning; “Pachycephalosaurus” http://www.enchantedlearning.com/subjects/dinosaurs/dinos/Pachy.shtml
5) American Museum of Natural History
http://www.amnh.org/exhibitions/expeditions/treasure_fossil/Fossils/Specimens/stegosaurus.html
The skull was given the scientific name: Sahelanthropus tchadensis and was nicknamed Toumai, which is a local name for a child born perilously close to the beginning of the dry season meaning “Hope of Life” (Walton). The skull has a mix of ape and hominid, early humans who are distinctly different from apes by their upright posture, features. The brain case is similar to those of apes, being about the size as a chimp, but the thick tooth enamel and the presence of small canines in the jaw bone are features that are similar to hominids. The most surprising part of the skull is the presence of the large brow ridges found on Toumai (Groves). This is unexpected because the next oldest hominid fossils have a small or non-existent brow ridges but our family, Homo, also has large prominent brow ridges (Gee).
Incisivosaurus Gauthier was what is believed to be a primitive Oviraptorosaurian that was recently discovered in China. The Theropod and its highly specialized skull is described as a bizarre creature that lived 128 million years ago (Gee). The characteristic that “sticks out” the most are it’s rodent-like teeth. Harry Gee has described the dinosaur as “a [cross between] Roadrunner [and] Bugs Bunny” (Ibid.) and Hillary Mayell calls it a “’Weird’ Bucktoothed Dino.” (Mayell)
developed by means of longer legs and arched heels - two traits seen in H. naledi fossils.
9[9] Trivedi, Bijal P. “Eggs Hold Skulls of Titanosaur Embryos.” National Geographic 27 September 2001.
The Thescelosaurus was a “bird-hipped” dinosaur or an ornithischian ( Russell 2). This herbivore lived near the end of the Cretaceous period, about one million years before the conclusion of the dinosaur era. Thescelosaurus was about the size of a short-legged pony, according to paleontologist Dr. Dale Russell and was native to North America from Wyoming up to Alberta, Canada.
As time progressed, Ichthyosaurs transitioned their body like features from a lizard-shaped body plan to a fish-shaped one through the early and middle Triassic periods. In 1927, the first bone fragments were foun...
Feder and Park present a list of traits that are used by paleoanthropologists to distinguish the appearance of skeletal features and characterize these changes over time. Th...
Every so often a discovery is made that attempts to shake up pre-conceived notions of how the dinosaurs actually lived or how they came to be. On June 22, 2000, in Oregon, scientists announced the discovery of the oldest known animal to have feathers. Though no records indicate how the age of the animal was determined, the fossil was dated at 220 million years old. It lived at the time of the very earliest dinosaurs, and about 75 million years before the first known bird.1[1]
This idea was reinforced when a Diplodocus (a type of sauropod that lived in the late Jurassic) skull was found in 1884 that contained a large hole in the top of the head. Scientists believed that this hole contained the entire nostril (Witmer 2001; ). This positioning of the nostrils was used for many other models of dinosaurs as well, but when it was discovered that...
The Hall of Saurischian Dinosaurs and the Hall of Ornithischian Dinosaurs are more examples of evolution within vertebrates. However, these two halls do not have much in common with our line of ancestry except for the fact that a backbone and brain case are present; any other things in common with our lineage are but minor details. That is why the AMNH has another hall called Mammals and Extinct Relatives.
The Jurassic period was the second segment of the Mesozoic Era. It occurred from 199.6 to 145.5 millions years ago, following the Triassic Period and preceding the Cretaceous Period. During the Jurassic Period, the supercontinent Pangaea split apart. Laurentia, the northern half, made up what would eventually form North America and Eurasia. The creation of these opened basins for the central Atlantic and the Gulf of Mexico. The southern half, Gondwana, drifted into an eastern segment that now forms Antarctica, Madagascar, India, and Australia, and a western portion that forms the present Africa and South America. This rifting, along with generally warmer global temperatures, allowed for diversification and dominance of the reptiles known as dinosaurs. Along with dinosaurs, several different types of life and rock formations emerged during the Jurassic period.
They ruled the world before the time of the dinosaurs, from the Cambrian Period to the
An interesting rumor is that the Triceratops might have never existed. Studies show that as Triceratops’ get older their frills smoothen and their horns get sharper. As they age they start to look like a totally different dinosaur called the Torosaurus (figure 2). Paleontologist found plenty of older Torosaurus fossils but never any of younger Torosaurus’. Can the Triceratops be a younger Torosaurus? Nobody knows the answer to that infamous question.
...d was made of thick bones and had a low cranial vault. Their face also consist of a big arching browridges just above their eyes (Stanford 302).
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