Paleo 200 -Final

Proterozoic Eon

Division of the Geologic Timescale from 2.5 billion years to 542 million years ago.

Silurian Period

Division of the Geologic Timescale from 440 to 420 million years ago.

Triassic Period

A division of the Geologic Time Scale from 252 to 201 million years ago; first period in of the Mesozoic Era; the start and end are marked by mass extinctions. Dinosaurs (e.g. Coelophysis and Herrerasaurus) and mammals first appeared in this division.

Phanerozoic Eon

Division of the Geologic Timescale from 542 million years ago to the present.

Permian Period

Division of the Geologic Timescale from 300 to 252 million years ago; ended in the largest mass extinction in Earth's history.

Paleozoic Era

Division of the Geologic Timescale from 542 to 252 million years ago that includes six geological periods.

Ordovician Period

Division of the Geologic Timescale from 490 to 440 million years ago; during this time the first jawed fish evolved; ended with a mass extinction.

Mesozoic Era

Division of the Geologic Timescale from 252 to 66 million years ago; contains the Triassic, Jurassic, and Cretaceous periods; during this time dinosaurs, birds, and mammals evolved; commonly called "the Age of Dinosaurs".

Archean Eon

Division of the Geologic Timescale from 4 to 2.5 billion years ago; during this time, the atmosphere likely lacked free oxygen and stromatolites first appeared.

Cambrian Period

Division of the Geologic Timescale from 542 to 490 million years ago. Huge explosion of life; sponges, molluscs, worms, first vertebrate relatives, and many kinds of arthropods (including trilobites) evolved.

Carboniferous Period

Division of the Geologic Timescale from 355 to 300 million years ago. Amphibians were widespread in the abundant
swamps, and reptiles, the first amniotes,
evolved. Much of the coal that is mined today
formed from rotting plants in swamps.

Cenozoic Era

Division of the Geologic Timescale from 66 million years ago to the present; often called "The Age of Mammals"

Devonian Period

Division of the Geologic Timescale from 420 to 355 million years ago. Huge jawed
fishes, like Dunkleosteus, evolved in the seas,
and the first true sharks appeared. Lobe-finned
'fishapods', like Tiktaalik, ventured onto land,
and give rise to the tetrapods.

Ediacaran Period

Division of the Geologic Timescale from 635 to 541 million years ago. The oldest fossil evidence of multicellular life comes from this time.

Hadeon Era

Division of the Geologic Timescale from 4.6 billion to 4 billion years ago; the first geologic eon

Jurassic Period

Division of the Geologic Timescale from 201 to 145 million years ago; the second period of the Mesozoic Era. Dinosaurs present include the Allosaurids, while the first birds, like Archaeopteryx, also evolve.

Cretaceous Period

Division of Geologic Timescale from 146-65 million years ago; the third period of the mesozoic Era. Dinosaurs present include Tyrannosaurs and Pachycephalosaurs.

The Crust

The outermost layer of the earth
consisting of the continents and ocean basins.

Alfred Wegener

Founder of the theory of plate tectonics.

Mantle

Highly viscous layer of the Earth; layer between the crust and the outer core; roughly 2900 km thick.

Lithosphere

Ridged outermost layer of the Earth; composed of the crust and the upper portion of the mantle.

Asthenosphere

The viscous layer of the upper mantle below the
lithosphere; between roughly 80 and 200 km below the Earth's surface

Inner Core

The innermost layer of the Earth; a solid mass composed of iron and nickel.

Outer Core

Layer of the Earth composed of molten iron and nickel; roughly 2270 km thick.

Plates

Pieces of the lithosphere affected by
convection currents.

Pangaea

Supercontinent, comprised of all the Earth's major
landmasses, that formed around 300 million years ago and began breaking up around 200 million years ago.

Panthalassa

The giant ocean that surrounded Pangaea.

Plate Tectonics

The movement of the lithosphere that provides the explanation for the drifting continents that Alfred Wegner theorized.

Diplodocids

A group of sauropod dinosaurs with long necks and long "whip-like" tails; lived during the Middle to Late Jurassic; examples: Apatosaurus, Diplodocus, Supersaurus

Macronarians

Group of Jurassic sauropods with robust bodies, front legs not noticeably shorter than their back legs, and that lack whip-lack tails. E.g. Brachiosaurus and Giraffatitan

Thyreophorans

Group of ornithischians with body armour. Includes e.g. Stegosaurs

Niche Partitioning

When similar animals avoid direct competition for
food resources, by exploiting different ecological niches e.g. predation vs scavenging

Ecological niche

An animal's role in the ecosystem; how it survives in that ecosystem.

Allosauroids

Large predators that originated in the Jurassic, with vertebrae that interlock more
rigidly, so their spines were held stiffer. Their
legs are also proportionately longer, suggesting
that they were faster than either megalosaurids
or ceratosaurids. E.g. Allosaurus

Coelurosaurs

Group of theropods that originated in the Jurassic, characterised by a long series
of sacral vertebrae, narrow hands, and tails with
back halves that are skinny, stiff, and
lightweight. the group from which birds arise.

Laurasia

Northern of the two supercontinents that were formed as Pangaea split in the Early Jurassic; comprised Asia, Europe, and
North America.

Gondwana

Southern of the two supercontinents that were formed as Pangaea split in the Early Jurassic; comprised Australia, Antarctica, Africa, South America, Madagascar and India.

Titanosaurs

Group of advanced sauropod dinosaurs; lived during the Late Jurassic to Late Cretaceous; globally distributed but most abundant in Gondwana; examples: Argentinosaurus,
Saltosaurus, Alamosaurus.

Carcharodontosaurids

A group of theropod dinosaurs with teeth that somewhat resemble those of modern sharks; lived during the Late Jurassic to Late Cretaceous; examples: Giganotosaurus, Carcharodontosaurus, Concavenator

Abelisaurids

A group of ceratosaurid theropods that thrived throughout Gondwana during the Middle Jurassic to Late Cretaceous; characterized by short forelimbs, small teeth, and ornamented skulls; examples: Carnotaurus, Majungasaurus, and Rugops.

Ankylosaurs

Heavily-armored quadrupedal ornithischian dinosaurs; examples: Ankylosaurus, Edmontonia, Polacanthus.

Nodosaurids

The second major group of
ankylosaurs. They lacked tail clubs, but some
have offensive weapons at the other end, in the
form of large osteoderm spikes that project
outwards from over their shoulders. E.g. Borealopelta

Ankylosaurids

The first major group of ankylosaurs.
The ankylosaurs with the famous tail clubs; also typically have large backwards-pointing horns at the rear of their skulls and a short rounded snout at the front.

Lambeosaurines

Advanced group of hadrosaurs with a big crest on their heads. Inside this crest is a complex and
hollow nasal passageway. E.g. Parasaurolophus

Hadrosaurines

Advanced group of hadrosaurs that lacked
complex sound amplifying crests. Some still did have small bony, or soft tissue crests. E.g. Edmontosaurus.

Marginocephalians

Diverse group of Laurasian dinosaurs that includes the ceratopsians and pachycephalosaurs. The name literally means "fringe heads" and refers to an overhanging lip of bone at the back margin of the skull.

Ornithomimids

Group of coelurosaurs that evolved a body plan similar to that of a modern ostrich or emu, but with long clawed forelimbs and a large tail.

Maniraptorans

Group of coelurosaurs that developed a highly specialized wrist bone called a semilunate carpal; includes birds, dromaeosaurs and oviraptorosaurs.

Dromaeosaurs

Group of maniraptoran theoropds with a large, sickle-shaped claw on each foot. E.g. Deinonychus

Oviraptorosaurs

Group of maniraptoran theropods that
adapted to a mostly vegetarian life and lost
their teeth in favour of large beaks. Many had cranial crests and fans of feathers on the ends of their tails.

Therizinosaurs

Bizarre group of maniraptoran theropods, with large hand claws, small skulls on the end of long necks and hind feet with four forward pointing toes. They also have a backwards-directed pubis and jaws with small herbivorous teeth in the back and a beak in the front.

Faunal interchange

When animals from one region can
move into another, leading to similar species in
both regions. E.g. Mongolian and W. Canadian dinosaurs.

Principle of Superposition

Chronological organisation of rock layers; the oldest rocks are at the bottom, and the layers
become increasingly younger towards the top.

Stratigraphy

The science of using the arrangement and composition of rock layers to interpret geological history.

A formation

A large, uninterrupted sequence of rock that is made of multiple layers that all share similar properties, and that all formed under similar conditions.

Radiometric Dating

The use of isotopic ratios to calculate age of a rock.

Radioactive Isotopes

Variations of an element that differ in the number of neutrons; has a specific half-life or rate of decay

The geologic time scale

A standardised series of chronological divisions that parses the Earth's history into discrete named units.

Stratigraphic Column

Geologic diagram that illustrates a sequence of rock layers, with the oldest at the bottom and the youngest at the top; often illustrates the thicknesses of each layer.

The Cambrian Explosion

Dramatic diversification of aquatic animal life
that occurred approximately 541 million years ago.

Trilobites

Extinct group of marine arthropods; first evolved during the Cambrian and died out at the End-Permian Mass Extinction.

Pterosaurs

Group of flying archosaurs closely related to dinosaurs; lived during the Late Triassic to the Cretaceous; the first group of vertebrates to evolve flight; examples: Quetzalcoatlus,
Rhamphorhynchus.

Plesiosaurs

A group of diapsids specially adapted to a marine life; lived during the Early Jurassic to Late Cretaceous; examples: Dolichorhynchops, Elasmosaurus, Kronosaurus

Pikaia

Thought to be one of the oldest known animals with a notochord; lived during the Cambrian.

Permo-Triassic Mass Extinction

The single largest mass extinction event in Earth history; occurred 252 million years ago and wiped out an estimated 96% of all marine life and 70% of all terrestrial life.

Pangaea

Supercontinent, comprised of all the Earth's major
landmasses, that formed around 300 million years ago and began breaking up around 200 million years ago.

Mosasaurs

A group of extinct lepidosaurs, related to modern snakes and monitior lizards, that were highly adapted to a marine life; evolved in the Late Cretaceous.

Ammonite

A kind of extinct marine cephalopod with a spiral shell; thrived from the Devonian through the
Cretaceous but died out during the End-Cretaceous Extinction.

The Burgess Shale

Fossil rich deposit in British Columbia, Canada; famous for its exceptional preservation of 505 million years old marine organisms

Isotope Ratio

The ratio of a naturally occurring radioactive isotope and its decay products

Ichthyosaurs

A group of marine reptiles that first evolved in the Triassic and went extinct towards the end of the Cretaceous. They look similar to dolphins, due to convergent evolution of body types. Name literally means: "fish lizard," even though they aren't fish or lizards!

Rhamphorhynchoids

Early group of flying reptiles, which were common in the Late Triassic and throughout the Jurassic. Typically had long tails compared to later flying reptiles

Pterodactyloids

Flying reptiles that differed to early relatives in morphology of their tails, which were short, and the carpels in their wrists, which were elongated and made a greater contribution to the length of the wing. Often had large head crests.

Anapsids

A group of amniotes that have no skull fenestrae; turtles are a modern example; note: the validity of this clade is contested among palaeontologists.

Synapsids

A group of amniotes with only one pair of fenestrae; includes mammals and their extinct close relatives.

Dimetrodon

Famous, sail-backed synapsid that lived during the Permian period. Often mistakenly identified as a dinosaur.

Diapsids

A group of amniotes with two pairs of skull fenestrae the: supratemporal and laterotemporal fenestrae. Includes crocodiles, lizards, snakes, tuataras, dinosaurs, birds, and many extinct groups.

Lepidosauromorphs

Group of non-archosaur diapsids that includes lizards, snakes, tuatara, and many extinct groups.

Archosauromorphs

A group of diapsids that includes archosaurs and many more primitive groups; first evolved during the late Permian.

Archosaurs

A group of advanced archosauromorph diapsids that includes crocodiles, dinosaurs, birds, and many extinct groups; characterised by mandibular and antorbital fenestrae.

Antorbital fenestra

Opening in the skull in front of the orbits; characteristic of archosaurs.

Mandibular fenestra

Opening in the lower jaws of archosaurs

Avemetatarsalians

Special group of archosaurs characterized by ankles that flex like a hinge. Includes dinosaurs, pterosaurs and some of their close relatives.

Pseudosuchians

Group of archosaurs that includes modern crocodilians and all archosaurs more closely related to crocodilians than to birds; "crocodile-line" archosaurs. Have a peg and socket ankle joint.

Gorgonopsids

Group of carnivorous synapsids characterised by sets of elongated fangs; lived from the Middle to Late Permian.

Dicynodonts

A group of herbivorous synapsids with characteristic tusks and beaks; first evolved in Permian and thrived during the Triassic.

Cynodonts

A group of synapsids that led to modern day mammals; first evolved in the Late Permian.

Charles Darwin

British naturalist who first conceived the theory of evolution.

Adaptation

An evolved trait that serves a specific function.

Heritable trait

A characteristic that is part of an organism's genetic code and has a chance to be copied to the organism's offspring.

Evolution

Theory that states that the differential
success of certain variations of a heritable trait,
because of competition for limited resources,
leads to the change over time of
that trait in a population.

Natural Selection

The competitive selective process by
which detrimental traits are competitively
discarded and advantageous traits are retained.

Dinosauria

A group formed by ornithischians, saurischians, their most recent common ancestor and all of its descendents.

Ornithischia

A group formed by all hadrosaurs, ceratopsians,
ankylosaurs, and stegosaurs, their most recent common ancestor and all of its descendents.

Saurischia

A group formed by the theropods, sauropods and prosauropods, their most recent common ancestor and all of its descendents.

Character

Any heritable trait that can be described and labelled.

Synapomorphy/Shared derived character

A character that is present in two or more groups and their common ancestor, but is not present in any more distantly related groups.

Convergent Evolution

The independent evolution of similar structures in two different lineages, usually due to both lineages facing similar ecological or environmental pressures.

Carl Linnaeus

18th century Swedish naturalist who created
binomial nomenclature

Taxonomy

The science of naming and allocating organisms into related groups.