The term dinosaur (Dinosauria, to be exact) was coined by British paleontologist Sir Richard Owen in 1842 and is derived from the Greek term “deinos” meaning reptile or lizard.
According to the available fossil record, dinosaurs first appeared on earth during the late Triassic period 240 million years from now and went extinct about 65 million years ago.
Dinosaurs are a varied group of animals from taxonomic, morphological, and ecological standpoints. The more we get to know about the dinosaurs, the more diverse they turn out to be, both from an ecological as well as a morphological point of view.
So far, about 700 valid species of dinosaur have been identified and named from more than 300 genera. Researchers, however, are certain that many are yet to be discovered. Below is a list of selected types of dinosaurs.
Dinosaurs can be broadly divided into two groups Saurischia and Ornithischia.
Saurischian (lizard-hipped) dinosaurs
Saurischian dinosaurs or Saurischia are dinosaurs that have reptile (or lizard-like) hip structure. Saurischian dinosaurs are further classified into Theropods and Sauropods. Theropods (Theropoda) are characterized by three-toed limbs and hollowed bones. Modern birds are believed to have evolved from theropod dinosaurs.
Sauropods, on the other hand, were larger with long tail and neck and walked on four legs instead of just two.
T-Rex specimen at the Carnegie Museum of Natural History | Image Courtesy: Scott Robert Anselmo
The tyrannosaurus rex, or T-Rex for short, is perhaps the most popular of all known dinosaur species. Based on the fossil specimens, researchers have estimated that a T-rex could grow more than 12 meters in length from head to tail.
T-rex is believed to have one of the strongest bite force in the animal kingdom that allowed it to hunt other dinosaurs effectively. What paleontologists still haven’t been able to conclude is that whether T-rex was an apex predator or a pure scavenger.
Analysis from the smallest partial T-rex specimen (LACM 28471) suggests that it might have weighed just 30 kg, while the largest known individual (FMNH PR2081) was well over 5,600 kg.
Velociraptor skeleton on display at Dinosaur Journey Museum in Fruita, Colorado
Velociraptor is a genus of theropod dinosaurs that lived in the latter half of the Cretaceous Period. So far, only two species of Velociraptor are discovered, namely V. mongoliensis and V. osmolskae.
Velociraptor (raptor for short) became a point of interest among the general public after its portrayal in the Jurassic Park movie series. As opposed to the movies, Velociraptor was a mid-sized dinosaur — an adult specimen measures about 2 m in length and 0.5 m in height. Their weight could have ranged anywhere from 15-19 kilograms.
While analyzing a Velociraptor fossil from Mongolia, researchers discovered feather quill knobs on its rear forearm. It’s a clear indication that the Velociraptor had feathers though they were flightless. Their unique claw is believed to be used to eviscerate or gut prey.
Spinosaurus skeleton at Japan Expo | Image Courtesy: Flickr/Kumiko
Existed During: Cretaceous period
Spinosaurus was among the largest of all known theropod dinosaurs that have ever lived rivaling the likes of Giganotosaurus and Tyrannosaurus.
Spinosaurus is known for its distinctive hump-like (or sail-like) spinal structure caused by over-extended vertebrae. The extended neural spines on the back of Spinosaurus were very tall, measuring at least 1.65 meters. Though its purpose is still not clear, experts have several theories, including heat-shielding and energy-storage.
The every first Spinosaurus remains were discovered in 1912, during an excavation in Western Egypt. However, the specimen was destroyed in the Second World War. Much of what we know about the dinosaur is from fossil specimens found in the latter half of the 20th century. So far, only two species of Spinosaurus have been identified.
Allosaurus (A. Fragilis) life restoration | Image Courtesy: Fred Wierum
Existed During: Late Jurassic Period
Allosaurus (meaning “different lizard”) was a typically giant carnivorous dinosaur that walked on earth during the late Jurassic Period about 155 million years ago. It is one of the most well-studied dinosaurs to date.
The Allosaurus genus has three valid species, the best known of which is A. fragilis. The species was about 8.5 m in length and weighed more than 2300 kg. As a bipedal dinosaur, its forelimbs were smaller than the hindlimbs.
Allosaurus most likely to have hunted relatively large herbivorous such as stegosaurids and ornithopods.
Restored holotype cast of Carnotaurus
Existed During: Late Cretaceous period
Discovered from the La Colonia Formation in Chubut Province, Argentina, Carnotaurus is one of the best-studied dinosaurs from the Southern Hemisphere. Most of what we know about the genus is, however, from just one well-preserved specimen of the species C. sastrei.
Carnotaurus was fairly distinctive than all known theropod dinosaurs – it had shorter, deeper skull and featured horns right above the eyes. Furthermore, it is distinguished by tiny or vestigial forelimbs. The only recovered Carnotaurus specimen was between 7.5 to 9 m in length and about 1350 kg in weight.
It was the first-ever bipedal dinosaur to have discovered with any notable skin impressions on its skeleton.
Deinonychus’ skeleton at the Field Museum of Natural History | Image Courtesy: Jonathan Chen
Existed during: Early Cretaceous Period
Deinonychus is a relatively small-sized theropod carnivorous dinosaur with only one known species, namely D antirrhopus. Fossil remains of Deinonychus have been found mostly from the Western and North-Western United States.
In 1964, paleontologist John Ostrom carried out a hunt in which more than one thousand Deinonychus fossils were discovered. The discovery and his subsequent findings practically changed how dinosaurs were perceived by the scientific community.
The study concluded that some non-avian dinosaurs were, in fact, warm-blooded with a high metabolism and are much closer to birds than the cold-blooded reptiles.
A fully matured Deinonychus could reach 3.4 m in length and weigh more than 70 kg. A study conducted in 2010 reveled that the bite force of Deinonychus was as high as 8,200 newtons, much greater than that of hyena.
Composite skeletal diagram of a Brachiosaurus specimen | Image Courtesy: Wikimedia Commons/Slate Weasel
Existed During: Jurassic Period
Brachiosaurus is one of the most well-studied sauropod dinosaurs to date. Its fossil remains were first discovered near the Colorado River valley in 1900 and was described by paleontologist Elmer Riggs three years later. Brachiosaurus is characterized by an extremely long neck, disproportionately small skull, and shorter hindlimbs.
Brachiosaurus appeared in the 1993 movie Jurassic Park among other dinosaurs, including Parasaurolophus, T-rex, and Triceratops.
A single dinosaur skeleton of D. carnegii at the Carnegie Museum of National History | Image Courtesy: Scott Robert Anselmo
Existed During: Jurassic Period
Diplodocus is a typical sauropod dinosaur genus with a long neck, whip-like tail, and stocky legs. It has been estimated that Diplodocus lived on earth during the Kimmeridgian age (154 -152 million years ago) of the Late or Upper Jurassic epoch.
Two species of Diplodocus (D. carnegii and D. hallorum) are known so far, both of which remain one of the longest dinosaurs on record. The fossil remains of Diplodocus are extensively found in the Morison Formation located in the western United States.
Researchers have been able to identify two more (possible) Diplodocus species. However, they are currently classified as doubtful species (nomen dubium) due to several inconsistencies.
Ornithischian (bird-hipped) dinosaurs
Ornithischia is an order of mostly herbivorous dinosaurs that are distinguished by their bird-like pelvic structure. Ornithischian dinosaurs can be broadly classified into two groups; Ceratopsia (horned-faced) and Thyreophora (shield-bearers).
Triceratops horridus skull at the Houston Museum of Natural Science | Image Courtesy: Christophe Hendrickx
Existed During: Cretaceous Period
The four-legged dinosaur with a bulky body and multiple horns on the skull, Triceratops, is perhaps the most easily recognized dinosaur genus discovered to date. It is also the best-known genus in the family Ceratopsidae, which includes large horned dinosaurs.
Triceratops’ were most likely to have hunted by large predators such as Tyrannosaurus – specific puncture wounds on their bones resemble teeth measurements of Tyrannosaurus.
It is believed to be one of the last few non-avian dinosaurs to walk on earth before the mass extinction event that took place about 66 million years ago. Recovered fossil remains indicate that an adult Triceratops specimen could weigh between 6000-12,000 kg and grow up to 9 m in length.
It is the official state dinosaur of Wyoming (U.S state) and serves as the state fossil of South Dakota.
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A composite skeleton of Stegosaurus ungulatus | Image Courtesy: Perry Quan
Existed During: Jurassic Period
Stegosaurus fossils were first uncovered in 1877, during the great dinosaur rush, also known as the Bone Wars. However, their anatomical structure was understood correctly only after a few years.
Stegosaurus genera belong to the group of armored dinosaurs known as Thyreophora and are characterized by distinctive double-row plates on its back.
So far, three valid species of Stegosaurus have been recognized. The largest known specimen weighed as much as 7,000 kg and grew up to 9 meters.
An artist’s impression of Ankylosaurus
Existed During: Cretaceous Period
Ankylosaurus first appeared on earth about 68 million years ago in the Late Cretaceous period. Only one species in the genus has been identified so far. The first-ever specimen of Ankylosaurus was discovered in 1906 by paleontologist Barnum Brown in the Hell Creek Formation, Montana.
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It had a wide, robust body and skull. The most notable characteristic of Ankylosaurus was, however, its armor – featuring protruding bone plates and knobs called osteoderms.
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