Dinosaur

Saurischia

What is a dinosaur?

Definition

The superorder or clade "Dinosauria" was formally named by the English scientist Richard Owen in 1842. The term is a combination of the Greek words deinos ("terrible" or "fearfully great" or "formidable") and sauros ("lizard" or "reptile"). Contrary to popular perception, the name was chosen to express Owen's awe at the size and majesty of the extinct animals; not out of fear or trepidation at their size and formidable arsenal.

Related Topics:
Superorder - Clade - English - Richard Owen - 1842 - Greek

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There is an almost universal consensus among paleontologists that birds are the descendants of theropod dinosaurs. Using the cladistic definition (all descendants of a single common ancestor), modern birds are dinosaurs, and dinosaurs are therefore not extinct:

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Ask your average paleontologist who is familiar with the phylogeny of vertebrates and they will probably tell you that yes, birds (avians) are dinosaurs. Using proper terminology, birds are avian dinosaurs; other dinosaurs are non-avian dinosaurs, and (strange as it may sound) birds are technically considered reptiles.—http://www.ucmp.berkeley.edu/diapsids/avians.htmlDinoBuzz, hosted by University of California Museum of Paleontology

Related Topics:
University of California - Paleontology

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Modern birds are classified by most palaeontologists as belonging to the subgroup Maniraptora, which are coelurosaurs, which are theropods, which are saurischians, which are dinosaurs.

Related Topics:
Bird - Maniraptora - Coelurosaur - Theropods - Saurischians

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However, birds are morphologically quite distinct from their reptilian ancestors, and referring to birds as "avian dinosaurs" and all other dinosaurs as "non-avian dinosaurs" is clumsy. Birds are still birds, at least in popular usage and among ornithologists. It is also technically correct, at least under the older Linnaean classification system, which accepts taxa that exclude some descendants of a single common ancestor (paraphyletic taxa). Paleontologists mostly use cladistics in their classifications, which does classify birds as dinosaurs, but many other scientists do not. As a result, this article hereafter uses "dinosaur" as a synonym for "non-avian dinosaur", and "bird" as a synonym for "avian dinosaur".

Related Topics:
Morphologically - Ornithologist - Linnaean classification - Paraphyletic - Cladistics

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Capabilities and behaviors

Dinosaurs are extremely varied. Some are herbivorous, others carnivorous; some bipedal, others quadrupedal. (For details on the various types of dinosaurs, see Classification below.)

Related Topics:
Herbivorous - Carnivorous - Biped - Quadruped - Classification

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Size

Only a tiny percentage of animals are ever fossilized, and most of these are still buried in the earth. As a result, the smallest and largest dinosaurs will probably never be discovered. Even among those that are recovered, very few are known from complete skeletons and even impressions of soft tissue like skin is rare. So reconstructing a skeleton by comparing the size and morphology of the bones to the bones of similar, better-known species is inexact; and restoring the muscles and other organs is at best educated guesswork.

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While the largest and smallest will probably remain unknown, and comparisons between existing specimens is imprecise, it is clear that as a group they were very large. But even by dinosaur standards the sauropods were gigantic. The smallest sauropods were larger than anything else in their habitat, and the largest were an order of magnitude more massive than anything else that has ever walked the Earth.

Related Topics:
Sauropod - Order of magnitude

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The tallest and heaviest dinosaur known from a complete skeleton is still the Brachiosaurus (now Giraffatitan), which was discovered in Tanzania between 1907–12, and is now mounted in the Humboldt Museum of Berlin. It is 12 m (38 ft) tall and probably weighed between 30,000–60,000 kg (30–65 tons). The longest is the 27 m (89 ft) long Diplodocus, which was discovered in Wyoming and mounted in Pittsburgh's Carnegie Natural History Museum in 1907.

Related Topics:
Brachiosaurus - Tanzania - Humboldt Museum - Berlin - 12 m - 30,000–60,000 kg - Diplodocus - Wyoming - Pittsburgh - Carnegie Natural History Museum

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There are bigger dinosaurs, but they are known from only a small handful of bones. The current record holders all date from the 1970s or later, and include the massive Argentinosaurus, which may have weighed 80,000–100,000 kg (90–110 tons); the longest, the 40 m (130 ft) long Supersaurus; and the tallest, the 18 m (60 ft) Sauroposeidon, which could have reached into a 6th-floor window.

Related Topics:
Argentinosaurus - 80,000–100,000 kg - 40 m - Supersaurus - Sauroposeidon

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No other group of terrestrial animals even comes close. The largest elephant on record weighed a mere 12,000 kg (13.5 tons), and the tallest giraffe was just 6 m (20 ft) tall. Even giant prehistoric mammals like the Indricotherium and the Columbian mammoth were dwarfed by the giant sauropods. Only a small handful of aquatic animals approach it in size, of which the blue whale is largest, reaching up to 190,000 kg (210 tons) and 33.5 m (110 ft) in length.

Related Topics:
Elephant - 12,000 kg - Giraffe - 6 m - Mammal - Indricotherium - Mammoth - Blue whale - 190,000 kg - 33.5 m

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Discounting modern birds like the bee hummingbird, the smallest dinosaurs known were about the size of a crow or a chicken. The Microraptor, Parvicursor, and Saltopus were all under 60 cm (2 ft) in length.

Related Topics:
Bee hummingbird - Crow - Chicken - Microraptor - Parvicursor - Saltopus - 60 cm

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Behavior

Interpretations of behavior based on the pose of a body fossil and its habitat, computer simulations of their biomechanics, and comparison with modern animals in similar ecological niches rely on speculation and promise to generate controversy for the foreseeable future. However, it is likely that at least the behaviors common in both of their closest living relatives, crocodiles and birds, are also common among dinosaurs.

Related Topics:
Habitat - Computer simulation - Biomechanics - Ecological niche

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The first evidence of herding behavior was the 1878 discovery of 31 Iguanodon that perished together in Bernissart, Belgium http://www.dinohunters.com/Iguanodon/bernissart_page.htm, and similar mass deaths and trackways suggest that herd or pack behavior is common among many dinosaur groups. Trackways of hundreds or even thousands of herbivores indicate that duck-bills (hadrosaurids) may have moved in great herds, like the American Bison or the African Springbok. Sauropod tracks document that they traveled in groups composed of several different species, at least in Oxford, England http://news.nationalgeographic.com/news/2002/05/0529_020529_sauropods.html, and others kept their young in the middle of the herd for defense according to trackways at Davenport Ranch, Texas. Dinosaurs may have congregated in herds for defense, migration, or to care for their young.

Related Topics:
Herd - Iguanodon - Bernissart - Belgium - Pack - Duck-bill - American Bison - Springbok - Oxford - Texas - Migration

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Jack Horner's 1978 discovery of a Maiasaura ("good mother dinosaur") nesting ground in Montana demonstrated parental care long after birth among the ornithopods http://www.isgs.uiuc.edu/faq/dino-faqs/pdq76.html http://www.browningmontana.com/dinosaurs.html, and similar nesting behavior and even huge nesting colonies like those of penguins have been discovered of other Cretaceous dinosaurs like the Patagonian sauropod Saltasaurus (in 1997). The Mongolian maniraptoran Oviraptor was even discovered in a chicken-like brooding position in 1993, which may mean it was covered with an insulating layer of feathers that kept the eggs warm http://search.eb.com/dinosaurs/dinosaurs/BRa.html. Trackways have also confirmed parental behavior among sauropods and ornithopods from the Isle of Skye in the United Kingdom http://news.bbc.co.uk/1/hi/scotland/3255494.stm. Nests and eggs are known from most major groups of dinosaurs, and it appears likely that dinosaurs communicated with their young, like modern birds and crocodiles.

Related Topics:
Jack Horner - Maiasaura - Nest - Montana - Ornithopod - Penguin - Patagonia - Saltasaurus - Mongolia - Maniraptora - Oviraptor - Chicken - Brood - Egg - Isle of Skye

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The crests and frills of some dinosaurs, like the marginocephalians, theropods and lambeosaurines, may have been too fragile for active defense, so they were probably used for sexual or aggressive displays, though little is known about dinosaur mating and territorialism. Communication is also an enigma, but the hollow crests of the lambeosaurines may have been resonance chambers used for a wide range of vocalizations.

Related Topics:
Crest - Marginocephalia - Theropod - Lambeosaurin - Territorialism - Communication - Resonance chamber - Vocalization

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Theropods stalked their prey in Glen Rose, Texas http://www.tpwd.state.tx.us/park/dinosaur/, and a fossil of a Velociraptor attacking a Protoceratops was discovered in the Gobi Desert in 1971 http://www.amnh.org/exhibitions/fightingdinos/ex-fd.html. While cannibalistic behavior among theropods is no surprise http://news.nationalgeographic.com/news/2002/12/1219_021219_dinocannibal.html, it was confirmed by tooth marks from Madagascar in 2003 http://www.nsf.gov/od/lpa/news/03/pr0336.htm.

Related Topics:
Glen Rose, Texas - Velociraptor - Protoceratops - Gobi Desert - Cannibal - Theropod

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Compared to the later mammalian radiation in the Cenozoic, there seem to be no burrowing and few climbing dinosaurs.

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Biomechanics has given insight into how fast dinosaurs could run http://palaeo.gly.bris.ac.uk/Palaeofiles/Tracks/Report7/Speed.html http://www.shef.ac.uk/~es/DINOC01/dinocal1.html, whether diplodocids could create sonic booms by snapping their tails like a whip http://www.newscientist.com/article.ns?id=mg15621103.900, whether giant theropods had to slow down to avoid fatal belly flops http://news.bbc.co.uk/1/hi/sci/tech/78905.stm, and if sauropods could float http://www.nserc.ca/news/features/dinosaurs_e.htm.

Related Topics:
Diplodocid - Sonic boom - Whip

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