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Pennsylvanian period

(Encyclopedia)Pennsylvanian period: see Carboniferous period. ...

Carboniferous period

(Encyclopedia)Carboniferous period kärbənĭfˈərəs [key], fifth period of the Paleozoic era of geologic time (see Geologic Timescale, tablegeologic timescale, table), from 350 to 290 million years ago. The pl...

synodic period

(Encyclopedia)synodic period sĭnŏdˈĭk [key], in astronomy, length of time during which a body in the solar system makes one orbit of the sun relative to the earth, i.e., returns to the same elongation. Because ...

Triassic period

(Encyclopedia)Triassic period trīăsˈĭk [key], first period of the Mesozoic era of geologic time (see Geologic Timescale, tablegeologic timescale, table) from 205 to 250 million years ago. Throughout the Triassi...

Tertiary period

(Encyclopedia)Tertiary period tûrˈshēĕrˌē [key], name for the major portion of the Cenozoic era, the most recent of the geologic eras (see Geologic Timescale, tablegeologic timescale, table) from around 26 to...

Quaternary period

(Encyclopedia)Quaternary period kwətûrˈnərē [key], younger of the two geologic periods of the Cenozoic era of geologic time (see Geologic Timescale, tablegeologic timescale, table) from 2 millon years ago to t...

sidereal period

(Encyclopedia)sidereal period, in astronomy, length of time a body takes to complete an orbit relative to the fixed stars. See sidereal time. ...

Silurian period

(Encyclopedia)Silurian period sĭlo͝orˈēən, sī– [key] [from the Silures, ancient tribe of S Wales, where the period was first studied; named by the British geologist R. I. Murchison], third period of the Pal...

Permian period

(Encyclopedia)Permian period pûrˈmēən [key] [from Perm, Russia], sixth and last period of the Paleozoic era (see Geologic Timescale, tablegeologic timescale, table) from 250 to 290 million years ago. Many ma...

trilobite

(Encyclopedia)CE5 Dorsal view of a trilobite trilobite trīˈləbītˌ [key], subphylum of the phylum Arthropoda that includes a large group of extinct marine animals that were abundant in the Paleozoic era. Th...