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(dī`nəsôr) [Gr., = terrible lizard], extinct land reptile of the Mesozoic eraMesozoic era
[Gr.,=middle life], major division of geologic time (see Geologic Timescale, table) from 65 to 225 million years ago. Great crustal disturbances that marked the close of the Paleozoic and the beginning of the Mesozoic eras brought about drastic changes in the
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. The dinosaurs, which were egg-laying animals, ranged in length from 2 1-2 ft (91 cm) to about 127 ft (39 m). Recognized discoveries of fossilized dinosaur bones date only to the 1820s; Sir Richard OwenOwen, Sir Richard,
1804–92, English zoologist and comparative anatomist. He studied medicine in Edinburgh and in 1827 joined the staff of the Hunterian museum of the Royal College of Surgeons, where he was first Hunterian professor of comparative anatomy and physiology
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, a Victorian anatomist, coined the term dinosaur.

Dinosaur Traits and Classification

Fossil remains of dinosaurs have been found in rock strata of every continent, indicating that they differed widely in structure, habitat, and diet. Their brain sizes varied, with some predators having brain-to-body ratios equivalent to those of some modern birds and animals. Many species built nests. Many theories regarding dinosaurs and their behavior have been hotly debated by the experts. These include the debate over the grouping of birds with dinosaurs, the question of whether nonavian dinosaurs were cold-blooded (ectothermic) or warm-blooded (endothermic), the question of whether dinosaurs protected and nurtured their young in the nest after hatching or whether the young were mobile and self-sufficient at birth, and the reason for the disappearance of nonavian dinosaurs.

No complete fossil dinosaur has ever been discovered. Inferences often must be made from fragments or pieces that have been compressed and distorted. Information about the diet has been gleaned from stomach contents and coprolites (fossilized dinosaur feces) and by comparing the teeth to those of living animals, for example, relating the large grinding teeth of hadrosaurs to those of living herbivores. Fossilized dinosaur footprints, such as the trackways found at Davenport Ranch in Texas, have been interpreted as evidence that some dinosaurs traveled in herds; bonebeds containing large numbers of certain dinosaurs, as have been found in Alberta, Canada, have also been seen as evidence of this. What is known about dinosaurs is that, far from being evolutionary failures, they dominated their habitats for much of their 160 million years of existence (the human species Homo sapiens has existed for approximately 150,000–200,000 years).

Although all dinosaurs were originally classified in a single order, they were later reclassified into two distinct types distinguished by structural differences. The pelvis in the saurischian (lizard-hipped) dinosaurs resembles that of still-extant reptiles, but in the ornithischian (bird-hipped) dinosaurs the pubic bone of the pelvis has forward and backward extensions that resemble those found in birds. (The backward-tilting hips of ornithischian dinosaurs and birds, however, have been determined to be the result of convergent evolution and not inheritance.) Many other shared characteristics have been noted between birds and saurischians, and it has come to be accepted by most paleontologists that modern birds are in fact extant dinosaurs, descended from the theropods of the saurischian order.

The jaws and teeth of the two dinosaur orders also differ. The saurischian order, which includes both herbivores and carnivores, has teeth around the entire jaw or confined to the front of the mouth. Ornithischians have "cheek teeth" along the sides of the jaw, but never in the front; the bones at the front of the mouth sometimes developed into the horny beaks typical of modern turtles. All known ornithischians were herbivores.

Dinosaurs have been further classified into some common groupings. In the saurischian dinosaurs, some were theropods [Gr., = beast feet], a group sharing hind feet with only three functional toes (e.g., the carnivorous bipeds TyrannosaurusTyrannosaurus
[Gr.,=tyrant lizard], member of a family, Tyrannosauridae, of bipedal carnivorous saurischian dinosaurs characterized by having strong hind limbs, a muscular tail, and short forelimbs. Tyrannosaurids are theropods, having three toes on the hind feet.
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, VelociraptorVelociraptor
[Gr.,=swift robber], swift bipedal carnivorous dinosaur of the late Cretaceous period. It was relatively small, being approximately 6 ft (1.8 m) long. It was similar to Deinonychus
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, DeinonychusDeinonychus
[Gr.,=terrible claw], swift bipedal carnivorous dinosaur of the early Cretaceous period, approximately 119–93 million years ago. Fossil specimens have been discovered in Montana and Wyoming. Adults were around 10 ft (2.5 m) from head to tail and 1 ft (3 m) high.
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, and possibly the living birds); others were sauropods [Gr., = lizard feet] with small heads and long necks (e.g., the herbivorous quadrupeds ApatosaurusApatosaurus
, [Gr.,=deceptive lizard], quadruped saurischian dinosaur, estimated to be from 70 to 90 ft (21 to 27 m) in length and to weigh up to 30 tons (27 metric tons). The similar dinosaur formerly called Brontosaurus [Gr.
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 [including those specimens formerly called Brontosaurus] and DiplodocusDiplodocus
[Gr., = double beam (or rafter)], immense quadruped herbivorous dinosaur found in the late Jurassic strata of the Colorado, Utah, and Wyoming. It had a long whiplash tail and a small horselike head with nostrils placed high, just below and between the eyes.
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). Among the ornithischians, there were ornithopods (bird-footed dinosaurs), such as IguanodonIguanodon
[Gr., = iguana tooth], herbivorous ornithiscian dinosaur, characterized by teeth similar to those of the iguana, a horny beak, spikelike thumbs, and a powerful tail. It may have been capable of walking on either two or four feet.
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; thyreophorans (armored dinosaurs), such as StegosaurusStegosaurus
[Gr.,=roof lizard], quadriped ornithischian dinosaur of the late Jurassic period. About 29 ft 6 in (9 m) long, it had short forelegs, four long bony spikes on a flexible tail, and two rows of upright triangular bony plates running along the back, which gave it a
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 and AnkylosaurusAnkylosaurus
, [Gr.,=crooked lizard], genus of heavily armored, herbivorous quadripedal dinosaurs, the best known of which is the species A. magniventris, the largest and heaviest of the ankylosaurs.
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; and ceratopsians (horned dinosaurs), such as TriceratopsTriceratops
[Gr., = three-horn face], genus of ornithischian quadruped dinosaurs of the late Cretaceous period. Because of some variations in sample fossils, it was thought at one time that there were as many as 16 different species, but only one species,
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. The total number of dinosaur genera that existed is unknown; new species are discovered every year, but some species, on further examination, are found to be redundant with earlier finds. One estimate of the possible number of distinct genera exceeds 1,800.

A study published in 2017 called into question a number of aspects concerning the dinosaur family tree. Relying on several hundred diagnostic anatomical features and including information based on new fossil discoveries in the late 20th and early 21st cent., the study compiled on a large statistical database concerning dinosaurs, which was analyzed by computer. The results suggested that the theropods share a common ancestor with the ornithischians, and the two groups have a common ancestor with the saurischians and the herrerasaurids, a group often considered to be theropods.

Similarities of dinosaurs found on what are now different continents have given scientists clues to the breakup of the supercontinent Pangaea, which began about 170 million years ago. For example, the discovery of a 130-million-year-old African dinosaur similar to the North American Allosaurus suggests that the African plate was connected to the northern continents (Laurasia) longer than had been believed previously.

The Extinction of the Dinosaurs

Many explanations have been offered for the worldwide extinction of the dinosaurs at the end of the Mesozoic after 160 million years of existence. One widely accepted theory is that one or more asteroids or comets hit the earth, lifting massive amounts of debris and sulfur in the air and blocking the sunlight from reaching the earth's surface. The 1991 discovery of the Chicxulub crater on the Yucatán peninsula in Mexico lent support to this idea. Another widely accepted theory is that the extinctions followed the huge volcanic eruptions that created the lava flows of the Deccan Traps in what is now India. It also has been suggested that both an impact or impacts and the eruptions may be responsible for the extinctions. (See mass extinctionmass extinction,
the extinction of a large percentage of the earth's species, opening ecological niches for other species to fill. There have been at least ten such events.
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 for more information.) No theory perfectly describes why nonavian dinosaurs, pterosaurs, and many marine organisms were affected by the extinction, when many mammals and other animals (e.g., turtles and crocodiles) survived. The extinction of the dinosaurs led to the geologically rapid evolution of mammals from a group of relatively small creatures to a diverse one that included many megafauna.


See R. Bakker, The Dinosaur Heresies (1986); D. Lambert, The Ultimate Dinosaur Book (1993); D. Lessem and D. Glut, The Dinosaur Encyclopedia (1993); P. Taquet, Dinosaur Impressions (1994, tr. 1998); M. A. Norell et al., Discovering Dinosaurs in the American Museum of Natural History (1995); J. R. Horner, Dinosaur Lives (1997); D. B. Weishampel et al., ed., The Dinosauria (2d ed. 2004); D. Nash, The Great Dinosaur Discoveries (2009); S. D. Sampson, Dinosaur Odyssey (2009).

The Columbia Electronic Encyclopedia™ Copyright © 2013, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/

What does it mean when you dream about dinosaurs?

In a dream, any creature can symbolize the animal self. As a long-extinct creature, a dinosaur can represent the sense that, at some level, we are the products of a very ancient process.

The Dream Encyclopedia, Second Edition © 2009 Visible Ink Press®. All rights reserved.


The name, meaning terrible lizard, applied to the fossil bones of certain large, ancient bipedal and quadripedal reptiles placed in the orders Saurischia and Ornithischia.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.


dinosaurs died out, unable to adapt to environmental change. [Ecology: Hammond, 290]
Allusions—Cultural, Literary, Biblical, and Historical: A Thematic Dictionary. Copyright 2008 The Gale Group, Inc. All rights reserved.


any extinct terrestrial reptile of the orders Saurischia and Ornithischia, many of which were of gigantic size and abundant in the Mesozoic era
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005


Any hardware requiring raised flooring and special power. Used especially of old minicomputers and mainframes, in contrast with newer microprocessor-based machines.

In a famous quote from the 1988 Unix EXPO, Bill Joy compared the liquid-cooled mainframe in the massive IBM display with a grazing dinosaur "with a truck outside pumping its bodily fluids through it". IBM was not amused.

Compare big iron; see also dinosaurs mating.


[IBM] A very conservative user; a zipperhead.
This article is provided by FOLDOC - Free Online Dictionary of Computing (foldoc.org)


Dinosaurs are always fascinating, sometimes lovable, mostly dangerous, and they are alive only in our imaginations. Consider all of the details of the dream and try to tie these ideas to some aspect of your life. The dinosaur, whether you have given it a positive or negative connotation, represents something from your past or an aspect of your personality that you have altered over time. Dinosaurs may represent old issues that have not been properly addressed and that continue to have the power to affect your life in the present.
Bedside Dream Dictionary by Silvana Amar Copyright © 2007 by Skyhorse Publishing, Inc.
References in periodicals archive ?
Attractions on the day included the opportunity to view a dinosaur hatching as well as coming face-toface with a life-size triceratops.
Claire goes to the rich man's mansion and shares with him her desire to bring into fruition a more systematic way of protecting dinosaurs. Lockwood has a fantastic idea: for his and his money to find people who will assist him in his desire to transfer the dinosaurs to another island where they will be allowed to live but without human presence and participation.
And today we know that many dinosaurs traveled in large groups, both parents were often when the eggs hatched and dinosaurs were not the solitary beings as was taught not all that many years ago.
Dr McNamara said: "There was a burst of evolution of feathered dinosaurs and birds at this time, and it's exciting to see evidence that the skin of early birds and dinosaurs was evolving rapidly in response to bearing feathers."
The place is so different and calm with small lakes, trees, lights and of course the roars of the dinosaurs,' said Saada al Touqi, an Omani visitor at the park.
Dinosaurs belong to a larger group called archosaurs that about 250 million years ago cleaved into two branches: crocodilians in one and another that includes dinosaurs, extinct flying reptiles called pterosaurs, and birds, which evolved from feathered dinosaurs.
Baron, a student at University of Cambridge, went to museums around the world, collecting data on dinosaurs. He fed the features, grooves, and shapes of different dinosaurs that he found, into a computer program.
Muscat: Those looking for a blend of education and entertainment can now have a unique experience at a dinosaur village in Amerat Park as an 'Edutainment' event is being held for the first time there as part of the Muscat Festival.
Whether all dinosaurs or just avian relatives flaunted feathers has been up for debate.
It's very cool to see these tracks and imagine dinosaurs walking around where you are standing.
A major new site for dinosaur fossils along the Yukon River has been discovered by researchers from the University of Alaska Museum of the North, Fairbanks.