Dinosaurs and their Relative

daughter element

in a radiogenic decay series, isotope that is final, stable decay product from the radioactive parent isotope

parent element

in a radiogenic decay series, the isotope that is radioactive and naturally decays to other elements through the loss of protons, neutrons, and electrons

Proterozoic

interval of geologic time between the Archean and the Paleozoic eras; from about 2.5 bya to 543 mya

period

interval of geologic time represented by a system of rock; the principal subdivisions of an era that are further divided into epochs

relative time scale

methods for tracking history in which events are known in relationship to the order of other events, but dates are not known

Priscoan

oldest interval of the Precambrian, older than the Archean; from about 4.6 to 4.0 bya

Paleogene

oldest period of the Cenozoic, younger than the Cretaceous and older than the Neogene; from 65 to 23 mya

era

one of the longest subdivisions of geologic time, consisting of one or more periods. Commonly used era names are Paleozoic, Mesozoic, and Cenozoic.

Pleistocene

one of two epochs of the Quaternary period, younger than the Pliocene and older than the Holocene; from 1.6 to 0.01 mya; time of the latest ice ages

Jurassic

period of geologic time during the Mesozoic era occurring after the Triassic and before the Cretaceous. The absolute age is from 208 to 146 mya.

proton

positively charged particle in the nucleus of an atom

Steno, Nicholas

Dane who, in 1820, proposed the principles of lateral continuity, original horizontality and superposition

absolute age

age of a rock in years, determined by radioactive dating

half-life

amount of time necessary for a naturally occurring radioactive element to decay so that only one half of the parent atoms remain

fossil

any direct indication preserved in rocks of the existence of former life

trace fossil

any indirect evidence of the existence of former life, commonly indicative of animal activity. Common types include burrows, trackways, and fossil excrement

body fossils

direct evidence of ancient life as represented by a former part of that organism

geologic time scale

division of relative time in Earth history consisting of several long eras of time and smaller subdivisions

Archean

domain of life that includes the prokaryotes distinguished from other prokaryotes at a molecular level

Phanerozoic

eon of geologic time including the Paleozoic, Mesozoic, and Cenozoic; from 543 mya to the present

Holocene

epoch of geologic time during the Cenozoic that includes the present time; geologic time younger than 10,000 years ago. Formerly known as Recent

Pliocene

epoch of the Neogene younger than the Miocene and older than the Pleistocene; from 5 to 1.6 mya

Eocene

epoch of the Paleogene occurring after the Paleocene and before the Oligocene; lasting from 56 to 35 mya

Permian

final period of Paleozoic Era, occurring after the Pennsylvanian and before the Triassic Period; named after the town of Perm in Russia; from 290 to 245 mya

relative age

geologic age of a rock or fossil defined in relation to the ages of other rocks and fossils rather than in years

epoch

interval of geologic time, intermediate in duration between longer periods and shorter ages; in this book most commonly used to describe the subdivisions of the Cenozoic

Triassic

intitial period of time during the Mesozoic Era, occurring before the Jurassic and after the Permian; lasting from 245 to 208 mya

Miocene

oldest epoch of the Neogene, older than the Pliocene and younger than the Oligocene; absolute age is 23 to 5 mya.

Paleocene

oldest epoch of the Paleogene, younger than the Cretaceous Period and older than the Eocene; from 65 to 56 mya

Paleozoic

oldest era of the Phanerozoic, younger than the Precambrian and older than the Mesozoic; from 543 to 245 mya

Cambrian

oldest period of the Paleozoic Era; younger than the Precambrian and older than the Ordovician, from 543 to 510 mya

neutron

one of the building blocks of atomic nuclei; lacks an electrical charge. Changes in the number of neutrons in atoms of an element result in different isotopes of that element

Oligocene

one of the epochs of the Paleogene, younger than the Eocene and older than the Miocene; from 35 to 23 mya

isotope

one of two or more forms of an element having the same atomic number (same number of protons and electrons) but differing in atomic weight (having different numbers of neutrons)

Carboniferous

period between the Devonian and the Permian in European classification. In North America the term Carboniferous is not used; it is replaced with the Mississippian and Pennsylvanian. The period is from 360 to 286 mya.

Cretaceous

period of geologic time that closes the Mesozoic Era, occurring between the Jurassic and the Paleogene Periods and lasting from 146 to 65 mya. The name is derived from the Latin word for chalk because chalk of a very common rock type from this period.

Neogene

period of the Cenozoic Era from 23 to 1.6 mya, younger than the Paleogene and older than the Quaternary

Silurian

period of the Paleozoic Era occurring after the Ordovician and before the Devonian; named after an ancient British tribe that inhabited n area in central England where rocks of this age were first found; from 439 to 408 mya

Devonian

period of the Paleozoic Era occurring after the Silurian and before the Mississipian; named after Devonshire in southwestern England. The absolute age of this period is 408 to 362 mya.

Pennslyvanian

period of the Paleozoic Era that occurs after the Mississippian and before the Permian Period; named after the coal-producing area of Pennsylvania. Basically equivalent to the Upper Carboniferous as used outside of North America; from 323 to 290 mya

Ordovician

period of the Paleozoic Era younger than the Silurian and older than the Cambrian; named after an early tribe in ancient Britain that lived in central Britain where these rocks were first described; from 510 to 439 mya

Mississippian

period of the Paleozoic older than the Pennsylvanian and younger than the Devonian; absolute age is 362 to 323 mya. Named for outcrops along the upper part of the Mississippi River in Illinois, Iowa, and Missouri. Outside of North America equivalent to the Lower Carboniferous

radioactivity

property of certain isotopes that makes them naturally unstable so that they change into other elements by the discharge of particles from the nucleus

Precambrian

rock, time, and Earth history prior to the beginning of the Paleozoic Era. From approximately 4.6 bya to 534 mya; includes the Priscoan, Archean, and Proterozoic Eras or the corresponding system of rocks

principle of superposition

stratigraphic concept proposed by Nicholas Steno stating that in an undisturbed sequence of sedimentary strata, the oldest strata are at the bottom and the youngest strata are at the top

principle of lateral continuity

stratigraphic concept proposed by Nicholas Steno stating that sedimentary strata continue for long distances geographically; concept true with the exception that distances can vary from being nearly continent-wide to the width of a stream channel

principle of original horizontality

stratigraphic concept proposed by Nicholas Steno stating that sedimentary strata were deposited in horizontal layers

global change

subdiscipline in which Earth processes are considered on a global basis to attempt to explain climatic and other variations through Earth history.

mass number

sum of the number of protons and neutrons in the nucleus of an atom. different isotopes of the same element have different mass numbers

Cenozoic

youngest era of geologic time, from 65 mya to the present. The term means "young life" or "recent life".

Quaternary

youngest period of geologic time, including the last 1.6 million years of Earth history; includes the Pleistocene and Holocene

Mesozoic

era of geologic time from 245 to 65 mya; the age of dinosaurs and ammonoids. the word means "middle life"