Tyrannosaurus (meaning 'tyrant lizard') is a
genus of
tyrannosaurid theropod dinosaur. The
species Tyrannosaurus rex, commonly abbreviated to
T. rex, is one of the dinosaurs most often featured in
popular culture around the world. It hails from what is now western
North America.
Like other tyrannosaurids, Tyrannosaurus was a bipedal carnivore with a massive skull balanced by a long, heavy tail. Relative to the large and powerful hindlimbs, Tyrannosaurus forelimbs were small and retained only two digits. Although other theropods rivaled or exceeded T. rex in size, it was the largest known tyrannosaurid and one of the largest known land predators, measuring over 13 metres (43 feet) in length and up to 7.5 tons in weight.
Fossils of some
T. rex have been found in North American
rock formations dating to the very end of the
Cretaceous Period (late
Maastrichtian stage, 65 million years ago); it was among the last dinosaurs to exist prior to the
Cretaceous-Tertiary extinction event. More than 30 specimens of
T. rex have now been identified, some nearly complete, which has allowed significant research into many aspects of its
biology, including its life history and
biomechanics. The feeding habits and potential speed of
T. rex remain controversial. (
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Iguanodon (meaning "Iguana tooth") is a
genus of
ornithopod dinosaur that lived roughly halfway between the first of the swift
bipedal hypsilophodontids and the ornithopods' culmination in the
duck-billed dinosaurs. Most
Iguanodon species lived between 140 to 120
million years ago, in the
Valanginian to
Barremian ages of the
Early Cretaceous Period of
Europe, although possible remains are known from
North America,
Asia, and
Africa.
Iguanodon's most distinctive features were its large
thumb spikes, which were possibly used for defence against
predators.
Discovered in 1822 and described three years later by English geologist Gideon Mantell, Iguanodon was the second dinosaur formally named, after Megalosaurus. Together with Megalosaurus and Hylaeosaurus, it was one of the three genera originally used to define Dinosauria. A large, bulky herbivore, Iguanodon is a member of Iguanodontia, along with the duck-billed hadrosaurs. The taxonomy of this genus continues to be a topic of study as new species are named or long-standing ones reassigned to other genera.
Scientific understanding of
Iguanodon has evolved over time as new information has been obtained from the fossils. The numerous specimens of this genus, including nearly complete skeletons from two well-known
bonebeds, have allowed researchers to make informed
hypotheses regarding many aspects of the living animal, including feeding, movement, and social behaviour. As one of the first scientifically well-known dinosaurs,
Iguanodon has occupied a small but notable place in the public's perception of dinosaurs, its artistic representation changing significantly in response to new interpretations of its remains. (
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Triceratops (meaning 'three-horned face') was a
herbivorous genus of
ceratopsid dinosaur that lived during the
late Maastrichtian stage of the Late
Cretaceous Period, around 68 to 65
million years ago (mya) in what is now
North America. It was one of the last dinosaurs to appear before the great
Cretaceous–Tertiary extinction event. Bearing a large bony
frill and three
horns on its large four-legged body and conjuring similarities with the modern
rhinoceros,
Triceratops is one of the most recognizable of all dinosaurs. Though it shared the landscape with, and was
preyed upon by the fearsome
Tyrannosaurus, it is unclear whether the two battled the way they are commonly depicted in movies and children's dinosaur books.
Although no complete skeleton has been found, Triceratops is well-known from numerous partial specimens collected since the introduction of the genus in 1887. The function of their frills and three distinctive facial horns has long inspired debate. Although traditionally viewed as defensive weapons against predators, the latest theories explain how these features were probably primarily used in display for courtship and dominance, much like the antlers and horns of modern reindeer, mountain goats or rhinoceros beetles.
Triceratops is the best-known of the ceratopsids, though the genus' exact placement within the group has been a point of contention amongst
paleontologists. Two
species,
T. horridus and
T. prorsus, are considered valid, although many other species have been named. (
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Diplodocus (meaning 'double bar') is a
genus of
diplodocid sauropod dinosaur whose fossilised skeleton was first discovered in 1878. The generic name refers to its double-beamed
chevron bones (
Greek diplos/διπλος meaning 'double' and dokos/δοκος meaning 'wooden beam' or 'bar') located in the underside of the tail. They were initially believed to be unique to
Diplodocus; however, they have since then been discovered in other diplodocids. It lived in what is now western
North America at the end of the
Jurassic Period.
Diplodocus was one of the more common dinosaurs found in the Upper
Morrison Formation, about 150 to 147
million years ago, in what is now termed the
Kimmeridgian and
Tithonian stages. This was an environment and time dominated by gigantic sauropod dinosaurs such as
Camarasaurus,
Barosaurus,
Apatosaurus and
Brachiosaurus.
Diplodocus is among the most easily identifiable dinosaurs, with its classic dinosaur shape, long neck and tail and four sturdy legs. For many years, it was the longest dinosaur known. Its great size may have been a deterrent to the predators
Allosaurus and
Ceratosaurus: their remains have been found in the same strata, which suggests they coexisted with
Diplodocus. (
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Stegosaurus (meaning 'roof-lizard') is a
genus of
stegosaurid armoured dinosaur from the
Late Jurassic period (
Kimmeridgian to
Early Tithonian) in what is now western
North America. However, in 2006 a specimen of
Stegosaurus was announced from
Portugal, suggesting that they were present in Europe as well. Due to its distinctive
tail spikes and plates,
Stegosaurus is one of the most recognisable dinosaurs, along with
Tyrannosaurus,
Triceratops and
Apatosaurus. At least three species have been identified in the upper
Morrison Formation and are known from the remains of about 80 individuals. They lived some 155 to 145
million years ago, in an environment and time dominated by the giant
sauropods Diplodocus,
Camarasaurus and
Apatosaurus. A large, heavily-built and
herbivorous quadruped,
Stegosaurus had a distinctive and unusual posture, with a heavily-arched back, short forelimbs, head held low to the ground and a stiffened tail held high in the air. Its array of plates and spikes have been the subject of much speculation. The spikes were most likely used for defence, while the plates have also been proposed as a defensive mechanism, as well as having display and
thermoregulatory (heat control) functions.
Stegosaurus was the largest of all the
stegosaurians (bigger than genera such as
Kentrosaurus and
Huayangosaurus) and, although roughly bus-sized, it nonetheless shared many anatomical features (including the tail spines and plates) with the other stegosaurian genera. (
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Velociraptor (meaning 'swift thief') was a
genus of
dromaeosaurid theropod dinosaur that existed approximately 83 to 70
million years ago during the later part of the
Cretaceous Period. There is only one currently recognized
species,
V. mongoliensis, although others have been assigned in the past.
Fossils of this species have been found in
central Asia, from both
Inner and
Outer Mongolia.
Smaller than other dromaeosaurids like Deinonychus and Achillobator, the turkey-sized Velociraptor nevertheless shared many of the same anatomical features. It was a bipedal carnivore with a long, stiffened tail and had an enlarged, sickle-shaped claw on each hindfoot, which is thought to have been used to kill its prey. Velociraptor can be distinguished from other dromaeosaurids by its long and low skull, with an upturned snout.
Due in large part to its prominent role in
Michael Crichton's novel
Jurassic Park and the subsequent
motion picture series,
Velociraptor (commonly shortened to 'raptor') is one of the dinosaur genera most familiar to the general public. It is also well-known to
paleontologists, with over a dozen recovered fossil skeletons — the most of any dromaeosaurid. One particularly famous specimen shows a
Velociraptor locked in combat with a
Protoceratops. (
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Compsognathus (meaning 'elegant jaw') was a small,
bipedal,
carnivorous theropod dinosaur. The animal was the size of a chicken and lived around 150
million years ago, during the early
Tithonian stage of the late
Jurassic Period, in what is now
Europe. Paleontologists have found two well-preserved fossils, one in
Germany in the 1850s and the second in
France more than a century later.
Compsognathus is one of the few dinosaurs for which the diet is known with certainty: the remains of small, agile lizards are preserved in the bellies of both specimens. Teeth discovered in
Portugal may be further fossil remains of the genus. Although not recognized as such at the time of its discovery,
Compsognathus is the first dinosaur known from a reasonably complete skeleton. Today,
C. longipes is the only recognized species, although the larger specimen discovered in France in the 1970s was once thought to belong to a separate species,
C. corallestris. Until the 1980s and 1990s,
Compsognathus was the smallest known dinosaur and the closest supposed relative of the early bird
Archaeopteryx. Thus, the genus is one of the few dinosaur genera to be well known outside of paleontological circles. (
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Albertosaurus (meaning 'Alberta lizard') was a
genus of
tyrannosaurid theropod dinosaur that lived in western
North America during the
Late Cretaceous Period, more than 70
million years ago. The
type species,
A. sarcophagus, was restricted in
range to the modern-day
Canadian province of
Alberta, after which the genus is named. Scientists disagree on the number of
species represented in the genus, recognizing either one or two species. As a tyrannosaurid,
Albertosaurus was a
bipedal predator with a massive head, jaws lined with dozens of large teeth and tiny, two-fingered 'hands' and it may have been at the top of the
food chain in its local
ecosystem. Although relatively large for a theropod,
Albertosaurus was much smaller than its more famous relative
Tyrannosaurus, probably weighing only as much as a modern
black rhinoceros.
Fossils of more than twenty individuals have been recovered, providing scientists with a more detailed knowledge of
Albertosaurus anatomy than is available for other tyrannosaurids. The discovery of ten individuals at one site provides evidence of pack behavior and allows studies of
developmental biology which are impossible with lesser-known animals. (
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Psittacosaurus (meaning 'parrot lizard') was a
genus of
psittacosaurid ceratopsian dinosaur from the Early
Cretaceous Period of what is now
Asia, about 130 to 100
million years ago. It is notable for being the most
species-rich dinosaur genus; At least eight
extinct species are recognized from
fossils found in different regions of
China and
Mongolia, with possible additional species from
Thailand and
Russia.
All species of Psittacosaurus were gazelle-sized bipedal herbivores characterized by a high, powerful beak on the upper jaw. At least one species had long, quill-like structures on its tail and lower back, possibly serving a display function. Psittacosaurs were extremely early ceratopsians and, while they developed many novel adaptations of their own, they also shared many anatomical features with later ceratopsians, such as Protoceratops and the elephant-sized Triceratops.
Psittacosaurus is not as familiar to the general public as its distant relative
Triceratops but it is one of the most completely known dinosaur genera. Fossils of over 150 individuals have been collected so far, including many near-complete skeletons. Most different age classes are represented, from nestling through to adult, which has allowed several detailed studies of
Psittacosaurus growth rates and
reproductive biology. The abundance of this dinosaur in the
fossil record has led to its use as an
index fossil for Early Cretaceous sediments of
central Asia. (
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Archaeopteryx (meaning 'ancient feather') is the earliest and most primitive known
avian to date. It lived in the late
Jurassic Period around 155-150 million years ago in what is now southern
Germany. At the time
Archaeopteryx lived,
Europe was an archipelago of islands in a shallow warm tropical sea, much closer to the equator than it is now.
Archaeopteryx lived during the time of the
dinosaurs, yet was set apart from them because of the inclusion of both avian and
theropod dinosaur features. Similar in size and shape to a
European Magpie, it bore broad, rounded wings and a long tail.
Archaeopteryx could grow to about half a metre, or 1.6 feet in length. Its
feathers resembled those of modern birds but
Archaeopteryx was rather different from any bird known today, in that it had jaws lined with sharp teeth, three 'fingers' ending in curved
claws and a long bony tail. These features, which are consistent with theropod dinosaurs, have made the
Archaeopteryx a hot topic in the debate on
evolution. Indeed, in 1862 the description of the first intact specimen of
Archaeopteryx, just two years after
Charles Darwin published
The Origin of Species, set off a firestorm of debate about evolution and the role of
transitional fossils that endures to this day. The eleven fossils currently classified as
Archaeopteryx are the oldest evidence of feathers on the planet and the only ones dated from Jurassic times. Furthermore, their advanced nature and placement suggest their origins must have been even earlier. All remains have been regarded by most as a single species, though this has been debated. (
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