Glossary I
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INDEHISCENT
Indehiscent fruit do not split open and release their seed when they mature.
INDEX FOSSILS
Index fossils are commonly found fossils that are limited in time span.
They help in dating other fossils. For example: trilobites were common
during the Paleozoic, but not found before the Cambrian period. Ammonites
were common during the Mesozoic Era, but not found after the Cretaceous
Period. Another example: the oldest-known ostracods are from the Cambrian
period; they became widespread during the Ordovician and remain so.
INDOSAURUS
(pronounced in-doh-SAWR-us) Indosaurus (meaning: "Indian lizard")was
a theropod dinosaur from the late Cretaceous Period, roughly 70 to 65
million years ago. This bipedal meat-eater had a thick braincase and a
wide skull; it may have had two horns on its head. It is known from a
partial skull found in Jabalpur, India, by Charles Matley. Indosuchus
was named by paleontologists von Huene and Matley in 1933. The type species
is I. matleyi.
INDOSUCHUS
(pronounced in-doh-SOOk-us) Indosuchus (meaning: "Indian crocodile")was
a theropod dinosaur from the late Cretaceous Period, roughly 70 to 65
million years ago. This bipedal meat-eater had many serrated teeth and
a narrow, crested skull with a flattened roof. It may have been up to
20 feet (6 m) long. It is known from a fragmentary skull found in India
by Charles Matley. It was related to, but smaller and more primitive than,
Allosaurus and Tyrannosaurus rex. Indosuchus was named by paleontologists
von Huene and Matley in 1933. The type species is I. raptorius.
INDRICOTHERIUM
Indricotherium is an extinct, hornless rhinoceros with relatively long
legs. (It used to be known as Baluchitherium). Adults were about 26 feet
(8 m) long, 18 feet (5.5 m) tall, and weighed about 17 - 18 tons (16 tonnes).
The skull was 4.25 feet (1.3 m) long. It was one of the biggest land animal
ever to live on Earth (Paraceratherium was even bigger). This herbivore
ate leaves and twigs from the tops of trees. It had four teeth; two tusk-like
front teeth in the top jaw pointed downwards and two on the bottom pointed
forwards. This extinct ungulate (hoofed mammal) had three toes on each
foot. It lived from the Oligocene to the early Miocene (toughly 40-26
million years ago). Fossils have been found in Asia (Pakistan, Mongolia
and China). Two of its enemies were the carnivores Hyaenodon and Dinictis.
Classification: Order Perissodactyla (odd-toed ungulates), Family Hyrachyidae
(odd-toed ungulates between tapirs and rhinos).
INGENIA
(pronounced in-JEE-nee-ah) Ingenia was a bird-like theropod dinosaur,
an oviraptorid. It was a bipedal omnivore about 4.5 feet (1.4 m) long.
It lived during the late Cretaceous Period, 80-70 million years ago and
was named in 1981 by R. Barsbold from Mongolian fossils.
INOSTRANCEVIA
Inostrancevia (named to honor the Russian geologist A. Inostrantzev) was
tiger-sized therapsid (a mammal-like reptile) that lived during the Permian
period, about 250 million years ago (before the time of the dinosaurs).
This carnivorous quadruped had sprawling legs and a large skull with long,
saber-like teeth. Fossils have been found in Russia (Arkhangelsk Region).
The type species is Inostrancevia alexandri; it was named by Vladimir
Prokhorovich Amalitzky in 1922.
Insect
Usually small to minute segmented animals which are members of the arthropods.
Insects are characterised by having a body that can be divided into three
distinct regions: the head, thorax and abdomen. They have six jointed
legs an usually one or two pairs of wings attached to the thorax. Insects
evolved in the Silurian period and in the Carboniferous period included
some very large forms including dragonflies with 70 cm wingspans. They
are still a very successful group today with over a million species identified.
Insectivore
An animal that feeds on insects.
Invertebrate
An animal that lacks a vertebral column or backbone. This group accounts
for more than 90 percent of living animals including, molluscs, arthropods,
and insects.
IRIDIUM
(pronounced irr-ID-ee-um) Iridium is a heavy metal element that is rare
on the Earth's surface, but abundant on chondritic meteors and in the
Earth's core.
IRIDIUM ANOMALY
The iridium anomaly is a layer of Earth's crust (the K-T layer, which
is about 65 million years old) in which there is excess of iridium (a
relatively rare element). The presence of this extra Iridium supports
the Alvarez asteroid theory, since this iridium may have come from an
asteroid.
IRRITATOR
(pronounced IRR-eh-tay-ter) Irritator was a theropod dinosaur, a spinosaurid
from the early Cretaceous Period. It is known from a nearly complete skull
(about 80 cm long) found in Brazil. Irritator challengeri was named by
paleontologists Martill, Cruikshank, Frey, Small and Clarke in 1996. The
people who found the snout-less skull added plaster to it in order to
make it look it more impressive. This nonsense didn't fool the paleontologists,
but it did irritate them, hence the name.
ISANOSAURUS
(pronounced ee-sahn-o-SAWR-us) Isanosaurus (meaning: "Isan lizard"
- Isan is the local name for the northeastern of Thailand) was a sauropod
dinosaur from the late Triassic Period (it is the earliest-known sauropod).
Fossils were found in the Nam Phong Formation, Thailand. Ischisaurus was
named by paleontologists Buffetaut, Suteethorn, Cuny, Tong, Le Loeuff,
Khansubha, and Jongautchariyakul in 2000. The type species is I. attavipachi.
ISCHIUM
(pronounced ISH-ee-um) The ischium (plural ischia) is a rod-like bone
that is part of the hip, or pelvic girdle.
ISOTOPE
An isotope of an element is another form of the same element that has
a different number of neutrons in the nucleus (giving it a different atomic
weight).
ITEMIRUS
(pronounced EYE-te-MEER-us) Itemirus (named for Itemir, the region of
Mongolia where it was found) was a small, theropod dinosaur from the late
Cretaceous Period, about 90 million years ago. This bipedal meat-eater
may have been a dromaeosaurid. A fossilized braincase (the part of the
skull that contains the brain) was found in Mongolia; very little is known
about this dinosaur since so little fossil material is known. Itemirus
was named by paleontologist Kurzanov in 1976. The type species is I. medullaris.