In 2012, a group of three "Triceratops" in relatively complete condition, each of varying sizes from a full-grown adult to a small juvenile, were found in Wyoming, near Newcastle. The remains are currently under excavation by paleontologist Peter Larson and a team from the Black Hills Institute. It is believed that the animals were traveling as a family unit, but it remains unknown if the group consists of a mated pair and their offspring, or two females and a juvenile they were caring for. The remains also show signs of predation or scavenging from "Tyrannosaurus", particularly on the largest specimen, with the bones of the front limbs showing breakage and puncture wounds from "Tyrannosaurus" teeth.
For many years, "Triceratops" finds were known only from solitary individuals. These remains are very common: one palaeontologist reported having seen 200 specimens of "T. prorsus" in the Hell Creek Formation of Montana, U.S. Similarly, Barnum Brown claimed to have seen over 500 skulls in the field. "Triceratops" teeth, horn fragments, frill fragments, and other skull fragments are abundant fossils in the latest Upper Cretaceous of western North America. It was the most dominant herbivore of the time. In 1986, Robert Bakker estimated it as making up 5/6ths of the large dinosaur fauna at the end of the Cretaceous.
"Triceratops" was one of the last ceratopsian genera to appear before the Cretaceous–Paleogene extinction event. The related "Torosaurus", and the more distantly related diminutive "Leptoceratops", were also present, though their remains are rarely found.
"Triceratops" were herbivorous, and because of their low head, their primary food was probably low growth, although they may have been able to knock down taller plants with their horns, beak, and bulk. The jaws were tipped with a deep, narrow beak, good for grasping and plucking.
"Triceratops" teeth were arranged in groups called batteries, of 36 to 40 tooth columns, in each side of each jaw with 3 to 5 stacked teeth per column, depending on the size of the animal. This gives a range of 432 to 800 teeth, of which only a fraction were in use at any given time (tooth replacement was continuous and occurred throughout the life of the animal). The great size and numerous teeth of "Triceratops" suggests that they ate large volumes of fibrous plant material, such as palms and cycads.
There has been much speculation over the functions of "Triceratops"' head adornments. The two main theories have revolved around use in combat, or display in courtship, with the latter thought now to be the most likely primary function.
"Triceratops" were long thought to have used their horns and frills in combat with predators such as "Tyrannosaurus". The idea was discussed first in 1917 and again 70 years later by Robert Bakker. There is evidence that "Tyrannosaurus" did have aggressive head-on encounters with "Triceratops", based on partially healed tyrannosaur tooth marks on a "Triceratops" brow horn and squamosal; the bitten horn is also broken, with new bone growth after the break. Since the "Triceratops" wounds healed, the "Triceratops" survived the encounter. "Tyrannosaurus" is also known to have fed on "Triceratops". Evidence for this includes a heavily tooth-scored "Triceratops" ilium and sacrum.
In addition to combat with predators using horns, "Triceratops" are classically shown engaging each other in combat with horns locked. While studies show that such activity would be feasible, if unlike that of present-day horned animals, there is disagreement about whether they did so.
The large frill also may have helped to increase body area to regulate body temperature. A similar theory has been proposed regarding the plates of "Stegosaurus", although this use alone would not account for the bizarre and extravagant variation seen in different members of the Ceratopsidae. This observation is highly suggestive of what is now believed to be the primary function, display.
The theory of their use in sexual display was first proposed by Davitashvili in 1961 and has gained increasing acceptance since. Evidence that visual display was important, either in courtship or in other social behavior, can be seen in the fact that horned dinosaurs differ markedly in their adornments, making each species highly distinctive. Also, modern living creatures with such displays of horns and adornments use them in similar behavior. A 2006 study of the smallest "Triceratops" skull, ascertained to be a juvenile, shows the frill and horns developed at a very early age, predating sexual development and thus probably important for visual communication and species recognition in general.
One skull, assigned to "Triceratops", has a hole in the jugal bone. It looks like a puncture wound sustained while the animal was still alive. This is supported by signs of healing that are present in the bone around the supposed wound. When examined closely, the hole in the bone has a diameter that is very similar to diameter of the distal end of a "Triceratops" horn. This is evidence of competition between individual dinosaurs.
Border
The border between two regions is a line, where one region is next to the other. If the regions are countries, the border can only be crossed at certain points. To cross the border, a passport or a visa might be necessary; such as the Wagah border between Pakistan and the Republic of India.
Genus
A genus is a rank in the biological classification (or taxonomy). It is above species, and below families. A genus can include more than one species. When biologists talk about a genus, they mean one or more species of animals or plants that are closely related to each other.
As with other taxa, the plural is different from other English words because it is a Latin word. 'Genus' is the singular, and 'genera' is the plural form of the word.
When printing the scientific name of an organism, the name is "always in italic". A name of species has two parts, with the genus first. For example, in ""Felis silvestris"", "Felis" is the genus. The genus name always begins with a capital letter. In ""Felis silvestris catus"", the third word is the subspecies, which is not often used.
In writing, genus names in Latin may be 'anglicised' to form a common name. For example, the genus "Pseudomonas" is "pseudomonad" (plural: "pseudomonads"). In practice, most really common animals and plants already have a common name. So instead of saying 'felids', or 'felines', one says 'cats' both for the family pet, and for all the cat family (Felidae).
Cretaceous
The Cretaceous period is the ninth and longest period in the Phanerozoic eon, lasting 80 million years from 145 to 65 million years ago (mya). It followed the Jurassic period, and is the third and last period of the Mesozoic era. After it came the Cainozoic era.
Though famous for its land fauna, the Cretaceous sea level rose much higher than today. North America was partly covered by an epicontinental inland sea, and half of Britain was under water.
In the Upper Cretaceous, chalk, a type of limestone, was laid down in warm shallow seas. Chalk is 95% to 99% made up of coccoliths, the calcium carbonate (CaCO3) plates which tiny single-celled algae (coccolithophorids) produce.
At its end came the famous meteorite strike which, with the volcanic flood basalts spewed out in the Deccan Plateau (India), ended so many of the dominant life-forms: see K/T extinction event.
The Cretaceous period has just two very long epochs:
The Lower Cretaceous at ~45 million years, is the longest epoch in the Phanerozoic eon.
Textbook
A textbook is a book used for the study of a subject. People use a textbook to learn facts and methods about a certain subject. Textbooks sometimes have questions to test the knowledge and understanding of the learner.