V >> Glossary Index
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Dinosaurs had long, heavy, reptilian tails. While some bipedal dinosaurs
may have used their tails as braces for standing upright, it seems that
the main purpose of tails in these dinosaurs was to counterbalance their
bodies when walking or running. Quadrupedal dinosaurs with long tails needed
them to counterbalance their long necks; such is the case of the sauropodomorphs.
The ankylosaurs and stegosaurs, however, had tails which may have served
as weapons. Deinonychus, Tenontosaurus, Ankylosaurus, and Stegosaurus.
Teeth are a useful tool for identifying dinosaur remains, since every dinosaur
tooth is distinctive. Scientists can tell whether the animal was a plant-eater
or a meat-eater, and sometimes they can use the teeth to gauge its size.
Carnivorous dinosaurs had sharp, pointed, blade-like teeth. Herbivorous
dinosaurs typically had leaf-shaped molars, although the shape of their
teeth shows greater variety than those of the meat-eaters. Dinosaurs with
both blade-shaped and leaf-shaped teeth may have eaten both plants and
meat, while dinosaurs with no molars or grinding teeth, such as the sauropods,
probably swallowed their food whole, depending upon gastroliths to grind
it for digestion. The worn teeth of some dinosaurs were continuously re-grown
throughout their lives. See Carnosaurs and Sauropods
Translation: Third Period
The Tertiary Period is the first of the two periods of the Cenozoic Era.
It immediately followed the Cretaceous Period (the last period of the Mesozoic
Era) and lasted from 66 million years ago to 2 million years ago. No dinosaur
fossils have been found in rocks of this age, and during this time mammals
became the dominant life form.
The Tetanurae (teh-tuh-NOOR-ree) are one of three infraorders of theropods.
This large group of theropods covers a great diversity of dinosaurs, including
the micro-orders Carnosauria (to which Tyrannosauridae belonged), and Coelurosauria
(to which several bird-like families belonged).
Named after the daughter of Oceanus in Greek mythology, Tethys was the
sea separating the two super continents Laurasia and Gondwanaland during
the Mesozoic Era.
Tetrapodite (TEH-tra-poh-dight) is the name given to rare dinosaur footprints
found in British Columbia and Alberta, Canada. Scientists believe that
they were made by a ceratopsian, which had rather massive, four-toed hind
feet and five-toed forefeet.
Thecodontia (thee-koh-DON-tee-ah) is an order of Triassic reptiles from
which dinosaurs, crocodilians, and pterosaurs, and possibly birds arose.
There were four suborders of thecodonts: Aetosauria, Phytosauria, Proterosuchia,
Thecodontosauridae (thee-koh-DON-toh-saw-ree-day) is a family of small,
primitive prosauropods. Whereas prosauropods as a whole were quadrupedal
some of the time and bipedal at others, thecondontosaurids were fully bipedal.
Translation: Beast Footed
Theropoda (thair-uh-PODE-ah) is one two suborders of saurischia. Theropods
were the carnivores of Dinosauria. They walked on strong hind legs, their
bodies parallel to the ground, tails outstretched to counterbalance the
weight of their bodies and heads. They lived during the Middle Triassic
through the Cretaceous Periods, and their sizes ranged from 7 inches (17
cm) to 50 feet (15 meters) in length. Infraorders of Theropoda are: Ceratosauria,
Tetanurae and Segnosauria.
Thyreophora (thye-REE-oh-FOR-ah) is one of three suborders of Ornithischia.
The size of these ornithischians ranged from small-to-large. They were
mostly quadrupedal (with the exception of more primitive species) and all
possessed body armor.
Translation: Large Lizards
The Titanosauridae (tye-tan-uh-SAWR-ih-day) was a family of sauropods.
Like most herbivores, they were equipped with stump-shaped teeth. Characteristically,
they had long hind legs and shorter front legs. They grew from 15 to 90
feet (27 meters) in length. Some titanosaurid remains show their backs
to be covered with embedded armor plates, and it is speculated that all
titanosaurids may have been similarly armored. These sauropods lived during
the Middle Jurassic through Late Cretaceous Periods.
Trackways are sites where fossilized dinosaur footprints have been found.
As dinosaurs walked or ran in sand or soft earth they left tracks which
were covered slowly by minerals and buried deep within the Mesozoic mud.
Fossilized footprints reveal to scientists many characteristics about dinosaurs.
For example, scientists can determine whether dinosaurs went into water,
if they were bipedal or quadrupedal, and how fast they were able to travel.
If footprints are discovered alone, it is difficult to conclude exactly
which dinosaur made them. However, if bones are discovered along with the
footprints, scientists can make several conclusions about the tracks. For
example, a trackway in Glen Rose, Texas, seems to indicate that dinosaurs
traveled in herds and that those herds were subject to predation by carnosaurs.
Dinosaur tracks must be carefully evaluated. For example, one set of tracks
was interpreted as those of a dinosaur hopping along like a kangaroo. Later,
it was demonstrated that the tracks were made by a dinosaur which was swimming
in water and occasionally touching the bottom. It is also not unusual to
discover the tracks of dinosaurs running up the faces of cliffs. These
tracks do not illustrate dinosaur mountain-climbing ability. They show,
rather, how the surface of the Earth has changed over the ages -- what
was once a seashore or a riverbed has been thrust from horizontal to vertical.
The Triassic (try-ASS-ik) Period is the first of the divisions of the Mesozoic
Era. (The other two periods are the Jurassic and the Cretaceous.) The Triassic
Period began 245 million years ago and ended 208 million years ago, and
it was toward the middle of the period that dinosaurs appeared. Evidence
suggests that at the beginning of the Triassic Period, before the appearance
of dinosaurs, the global temperature averaged around 50º to 60º
F (10º to 15º C). Toward the end of period, however, the global
climate began to become drier and hotter; deserts began to appear on much
of Pangaea's surface area. In the northern hemisphere, gingko and tree
fern forests flourished, while near the equator were forests of conifers
and cycads. Horsetails grew near bodies of water.
Translation: Gnaw Tooth
The Troödontidae (troh-uh-DON-tih-day) is a branch of small theropods
(falling into the Maniraptora branch) who possessed the largest brains
of any dinosaur yet discovered. Their heads were narrow and long, with
slender jaws bearing small, densely-spaced teeth. The hind limbs were also
slender and very long, with large, clawed second toes.
Translation: Tyrant Lizard
The Tyrannosauridae (tye-ran-uh-SAWR-ih-day) were a family of carnosaurs
that lived during the Late Cretaceous Period. Like all theropods, tyrannosaurs
were bipedal; that is, they strode on two legs with their bodies held close
to horizontal and their tails outstretched for balance. They had very short
but powerful arms and powerfully built legs. Heavier than earlier carnosaurs,
tyrannosaurs reached weights of up to 14,000 lbs (6350 kg) and grew to
lengths of 50 feet (15 meters) and more. They were equipped with huge,
strong jaws and sharp, serrated teeth. They may have hunted in packs, and
it is thought that they were relatively fleet of foot. One recently expressed
opinon would make tyrannosaurs mere scavengers, but this idea is debatable.
Tyrannosaurids have been discovered in North America, Mongolia, India,