Dinosaur

What is Dinosaurs?

Dinosaurs are a diverse group of animals that were the dominant terrestrialvertebrates for over 160 million years, from the late Triassic period (about 230million years ago) until the end of the Cretaceous (about 65 million years ago), when the Cretaceous–Paleogene extinction event led to the extinction of most dinosaur species at the close of the Mesozoic era. The fossil record indicates thatbirds evolved within theropod dinosaurs during the Jurassic period. Some of them survived the Cretaceous–Paleogene extinction event, including the ancestors of all modern birds. Consequently, in modern classification systems, birds are considered a type of dinosaur—the only group of which that has survived to the present day.


Dinosaurs are a diverse and varied group of animals; birds, at over 9,000 species, are the most diverse group of vertebrate besides perciform fish. Paleontologists have identified over 500 distinct genera and more than 1,000 different species of non-avian dinosaurs.Dinosaurs are represented on every continent by both extant species and fossil remains. Some dinosaurs are herbivorous, others carnivorous. Many dinosaurs, including birds, have been bipedal, though many extinct groups were quadrupedal, and some were able to shift between these body postures. Many species possess elaborate display structures such as horns or crests, and some prehistoric groups developed even more elaborate skeletal modifications such as bony armor. Avian dinosaurs have been the planet's dominant flying vertebrate since the extinction of the pterosaurs. Although generally known for the large size of some species, most Mesozoic dinosaurs were human-sized or even smaller. All known dinosaurs are known to have built nests and laid eggs.

The term "dinosaur" was coined in 1842 by the English paleontologist Richard Owen, and derives from Greek (deinos) "terrible, powerful, wondrous" + (sauros) "lizard". Through the first half of the 20th century, most of the scientific community believed dinosaurs to have been sluggish, unintelligent cold-blooded animals. Most research conducted since the 1970s, however, has indicated that dinosaurs were active animals with elevated metabolisms and numerous adaptations for social interaction.

Since the first dinosaur fossils were recognized in the early 19th century, mounted fossil dinosaur skeletons or replicas have been major attractions at museums around the world, and dinosaurs have become a part of world culture. They have been featured in best-selling books and films such as Jurassic Park, and new discoveries are regularly covered by the media. In informal speech, the word "dinosaur" is used to describe things that are impractically large, obsolete, or bound for extinction, reflecting the outdated view that dinosaurs were maladapted monsters of the ancient world.[citation needed]
 

Key words :

The Triassic is a geologic period that extended from about 250 to 200 Mya (million years ago). As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic.

Vertebrates  are members of the subphylum Vertebrata, chordates with backbones and spinal columns. Vertebrates are the largest group of chordates with currently about 58,000 species described.[2] Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds.

Cretaceous is a geologic period and system from circa 145.5 ± 4 to 65.5 ± 0.3 million years (Ma) ago.

The Mesozoic Era is an interval of geological time from about 250 million years ago to about 65 million years ago. It is called the Age of Dinosaurs because of its association with non-avian dinosaurs

Fossils (from Latin fossus, literally "having been dug up") are the preserved remains or traces of animals (also known as zoolites), plants, and other organisms from the remote past. The totality of fossils, both discovered and undiscovered, and their placement in fossiliferous (fossil-containing) rock formations and sedimentary layers (strata) is known as the fossil record.

Evolution (also known as biological or organic evolution) is the change over time in one or more inherited traits found in populations of organisms. Inherited traits are particular distinguishing characteristics, including anatomical, biochemical or behaviouralcharacteristics, that are passed on from one generation to the next.

Theropods (theropod suborder name Theropoda meaning "beast feet") is both a suborder of bipedal saurischian dinosaurs, and a clade consisting of that suborder and its descendants (including modern birds).

The Jurassic is a geologic period and system that extends from about 199.6± 0.6 Mya (million years ago) to 145.5± 4 Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic Era, also known as the Age of Reptiles

The Perciformes, also called the Percomorphi or Acanthopteri, is one of the largest orders of vertebrates, containing about 40% of all bony fish. Perciformes means perch-like. They belong to the class of ray-finned fish and comprise over 7,000 species found in almost all aquatic environments.

Palaeontology is the study of prehistoric life, including organisms' evolution and interactions with each other and their environments (their paleoecology). As a "historical science" it tries to explain causes rather than conduct experiments to observe effects. Paleontological observations have been documented as far back as the 5th century BC.

In biology, a genus (plural: genera) is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia. The composition of a genus is determined by a taxonomist. The standards for genus classification are not strictly codified, and hence different authorities often produce different classifications for genera. In the hierarchy of the binomial classification system, genus comes above species and below family.

Extant is a term commonly used in biology to refer to taxa, such as species, genera and families that are still in existence, meaning still alive.

Bipedalism is a form of terrestrial locomotion where an organism moves by means of its two rear limbs, or legs. An animal or machine that usually moves in a bipedal manner is known as a biped meaning "two feet".

Quadrupedalism is a form of land animal locomotion using four limbs or legs. An animal or machine that usually moves in a quadrupedal manner is known as a quadruped, meaning "four feet".

Armour (or armor, see spelling differences) in animals is external or superficial protection against attack by predators, formed as part of the body (rather than the behavioural use of protective external objects), usually through the hardening of body tissues, outgrowths or secretions.

Pterosaurs from the Greek pterosauros, meaning "winged lizard") were flying reptiles of the clade or order Pterosauria. They existed from the late Triassic to the end of the Cretaceous Period (220 to 65.5 million years ago). Pterosaurs are the earliest vertebrates known to have evolved powered flight.

Sir Richard Owen, KCB (20 July 1804 – 18 December 1892) was an English biologist, comparative anatomist and palaeontologist.

A poikilothermis an organism whose internal temperature varies considerably. It is the opposite of a homeotherm, an organism which maintains thermal homeostasis. Usually the variation is a consequence of variation in the ambient environmental temperature

Metabolism (from Greek (metabolismos), "outthrow") is the set of chemical reactions that happen in living organisms to maintain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories. Catabolism breaks down organic matter, for example to harvest energy in cellular respiration. Anabolism uses energy to construct components of cells such as proteins and nucleic acids.

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