Chapter 30: Vocabulary – Views of Earth’s Past
In your own words, rewrite the definition and draw a picture to illustrate the meaning.
Ammonite: A fossil cephalopod that is an important index fossil of the Triassic Period.
Bipedal: Walking upright on two legs.
Crinoid: A sea lily, a relative of the sea star, common during the Mississippian Period.
Dinosaur: One of many forms of now extinct animals that dominated the Mesozoic Era.
Eon: The first division of the geologic time scale and therefore the longest.
Epoch: A subdivision of a geological period on the geologic time scale.
Era: A major division of geologic time.
Eurypterid: A sea animal that was common during the Silurian Period; also called a sea
scorpion.
Evolution: The process of change that produces new life forms over time.
Foraminifera: Single-celled organisms with calcite shells common during the
Mississippian Period.
Geologic time scale: A summary of major events in Earth’s history that are preserved in
the rock record.
Graptolite: Tiny sea animals that lived in colonies; used as index fossils of the Ordovician
Period.
Hominid: Modern human or humanlike ancestor.
Natural selection: The theory that organisms that survive to produce offspring have
inherited the most favorable traits for survival in a particular environment.
Period: A subdivision of a geologic era.
Precambrian: All the geologic time before the start of the Cambrian period in the
Paleozoic Era.
Shield: The exposed area of the oldest rocks, or craton, of a continent.
Stomatolite: A layered dome or column formed of trapped sediments and mats of
cyanobacteria.
Trilobite: A crablike invertebrate that is the most common fossil of the Cambrian Period