Amber—a hard, yellowish, translucent, fossilized plant resin.
Ammonite—ammonoid cephalopod with complexly wrinkled suture pattern;
member of subclass Ammonoidea.
Anterior—front or fore.
Anus—the terminal opening of the alimentary canal, through which waste
matter is discarded from the body.
Aperture—the opening of shells, cells, etc.
Aragonite—calcium carbonate (CaCO₃) crystallizing in a different form
than calcite. In shells it is chalky and opaque; is less stable than
calcite.
Archeozoic—the oldest known geological era; early Precambrian time.
Articulated—joined by interlocking processes or by teeth and sockets.
Asymmetrical—without or lacking symmetry.
Bilateral—pertaining to the two halves of a body as symmetrical and
mirror images of each other.
Binomial nomenclature—system of scientific nomenclature requiring two
names: generic and trivial.
Blastoid—stalked echinoderm with bud-like calyx usually consisting of 13
plates; member of class Blastoidea.
Brachiopod—bivalved marine invertebrate; member of phylum Brachiopoda.
Brackish—a mixture of salt and fresh waters.
Burrow—a hole in the ground, rock, wood, etc., made by certain animals
for shelter or while gathering food.
Calcareous—composed of, or containing, calcium carbonate; limy.
Calcite—calcium carbonate (CaCO₃) crystallizing in a different form than
aragonite. In shells it is translucent and more stable than aragonite.
Cambrian—the first (oldest) period of the Paleozoic era.
Calyx—in corals the bowl-shaped depression in the upper part of the
skeleton; in stalked echinoderms that part of the body which contains
most of the soft parts.
Caprinid—a Cretaceous pelecypod that is typically coiled in the form of
a ram’s horn.
Carapace—the hard protective covering that forms the exoskeleton of many
invertebrates; in arthropods it is usually chitinous or
calcaro-chitinous.
Carbonization—the process of fossilization whereby organic remains are
reduced to carbon or coal.
Cast—the impression taken from a mold.
Cenozoic—the latest era of geologic time, following the Mesozoic era and
extending to the present.
Cephalon—the head; in trilobites the anterior body segment forming the
head.
Cephalopod—marine invertebrate with well-defined head and eyes and with
tentacles around the mouth; member of class Cephalopoda, phylum
Mollusca; includes squids, octopuses, pearly nautilus.
Ceratite—an ammonoid cephalopod with suture composed of rounded saddles
and jagged lobes; member of subclass Ammonoidea.
Chert—a cryptocrystalline variety of silica; flint is a variety of
chert.
Chitin—a horn-like substance, found in the hard parts of many animals,
such as beetles, crabs, etc.
Chitinous—composed of chitin.
Cirri—in crinoids, the jointed appendages which branch off the side of
the stem or from the base of some crinoid stems.
Coelenterate—invertebrates characterized by a hollow body cavity, radial
symmetry, and stinging cells; a member of phylum Coelenterata;
includes jellyfishes, corals, sea anemones.
Colonial—in biology refers to the way in which some invertebrates live
in close association with, and are more or less interdependent upon,
each other; colonial corals, hydroids, etc.
Columella—a small column or central axis; in corals the small rod or
axial pillar in the center of the corallite; in gastropods the solid
or perforate pillar formed by the union of the successive coils of a
conispiral shell.
Columnal—one of the disk-shaped segments of a crinoid stalk.
Concentric—having a common center, as circles; refers to shell markings
that are parallel to shell margin.
Concretion—nodular or irregular masses in sedimentary rocks and usually
formed around a central core, which is often a fossil.
Conical—cone-shaped.
Conodont—minute tooth-like fossils found in certain Paleozoic rocks;
their origin is not definitely known, but they may have been part of
some type of extinct fish.
Coral—bottom-dwelling marine invertebrate that secretes calcareous hard
parts; member of class Anthozoa, phylum Coelenterata.
Corallite—the skeleton formed by an individual coral animal; may be
solitary or form part of a colony.
Corallum—the skeleton of a coral colony.
Corona—crown; in echinoids the main part of the skeleton consisting of
symmetrically arranged calcareous plates.
Coprolite—the fossil excrement of animals.
Correlation—the process of demonstrating that certain strata are closely
related to each other or that they are stratigraphic equivalents.
Cretaceous—the third and last period of the Mesozoic era.
Cystoid—an extinct stemmed echinoderm with calyx composed of numerous
irregularly arranged plates; member of class Cystoidea.
Dendritic—resembling a tree, branching.
Dentition—the system or arrangement of teeth peculiar to any given
animal.
Devonian—the fourth oldest period of the Paleozoic era, follows the
Silurian, precedes the Mississippian.
Dip—the angle of inclination which the bedding plane of rocks makes with
a real or imaginary horizontal line.
Distillation—in fossils that process by which volatile organic matter is
removed, leaving a carbon residue.
Dolomite—a mineral composed of calcium magnesium carbonate (CaMg(CO₃)₂).
Dorsal—pertaining to the back.
Echinoderm—a marine invertebrate with calcareous exoskeleton and usually
exhibiting a five-fold radial symmetry; member of phylum
Echinodermata; includes cystoids, blastoids, crinoids, starfishes, and
sea urchins.
Echinoid—bottom-dwelling, unattached marine invertebrate with
exoskeleton of calcareous plates covered by movable spines; member of
class Echinoidea; sea urchins, heart urchins, biscuit urchins.
Endoskeleton—the internal supporting structure of an animal.
Eocene—the next to earliest of the Tertiary epochs, follows the
Paleocene and precedes the Oligocene.
Equivalved—right and left valves subequal and (except for hinge
structures) comprising mirror images of each other.
Evolution—a term applied to those methods or processes and to the sum of
those processes whereby organisms change through successive
generations.
Exoskeleton—an external skeleton, or hard covering for the protection of
soft parts, particularly among invertebrates.
Fault—the displacement of rocks along a zone of fracture.
Fauna—an assemblage of animals (living or fossil) living in a given
place at a given time.
Flank—the side or lateral portion of anything.
Flora—an assemblage of plants (living or fossil) living in a given place
at a given time.
Fold—in brachiopods, a major rounded elevation of shell which affects
both inner and outer shell surfaces.
Foramen—in brachiopods, the opening in the pedicle valve near the beak
where the pedicle extends through the shell.
Foraminifer—a protozoan usually possessing a calcareous, perforated,
chambered shell, but shell may be chitinous or agglutinated; a member
of the order Foraminifera, phylum Protozoa.
Formation—a rock unit useful for mapping and distinguished primarily on
the basis of lithologic characters.
Fossil—the remains or traces of organisms buried by natural causes and
preserved in the earth’s crust.
_Guide fossil_—a fossil which, because of its limited vertical but wide
horizontal distribution, is of value as a guide or index to the age of
the rocks in which it is found.
Fossiliferous—containing fossilized organic remains.
Fusulinid—a spindle-shaped foraminifer: test shaped like a grain of
wheat.
Gastrolith—highly polished well-rounded pebbles found associated with
certain reptilian fossils; “stomach stones.”
Gastropod—a terrestrial or aquatic invertebrate, typically possessing a
single-valved, calcareous, coiled shell; member of class Gastropoda,
phylum Mollusca: snails and slugs.
Geologic age—the age of an object as stated in terms of geologic time
(e.g., a Pennsylvanian fern, Cretaceous dinosaur).
Geologic map—map showing distribution of rock outcrops, structural
features, mineral deposits, etc.
Geologic range—the known duration of an organism’s existence throughout
geologic time (e.g., Cambrian to Recent for brachiopods).
Glauconite—a greenish mineral commonly formed in marine environments and
essentially a hydrous silicate of iron and potassium.
Goniatite—an ammonoid cephalopod with suture composed of smooth saddles
and simple angular lobes; member of subclass Ammonoidea.
Graptolite—an extinct, marine, colonial organism with chitinous hard
parts; believed to belong to subphylum Hemichordata of phylum
Chordata.
Guide fossil—see Fossil.
Habitat—the physical environment in which an organism lives.
Hinge-line—in brachiopods, the edge of the shell where the two valves
articulate; in pelecypods, the dorsal margin of the valve which is in
continual contact with the opposite valve.
Igneous rock—rocks which have solidified from lava or molten rock called
magma.
Index fossil—see Fossil.
Inequivalved—opposite valves unlike in shape or size, or both.
Jurassic—second oldest period of the Mesozoic; follows the Triassic,
precedes the Cretaceous.
Keel—a strong continuous ridge along the ventral side of ammonites.
Larva—the young form of some animals before they assume the mature
shape.
Lateral—side or to the side.
Lithology—the study and description of rocks based on the megascopic
(with the naked eye) examination of samples. Used also to refer to the
texture and composition of any given rock sample.
Living chamber—in mollusks, that part of the shell which is occupied by
the living animal.
Lobe—in cephalopods, the backward flexure of the suture or septum.
Longitudinal—in a direction parallel with the length.
Lophophore—in brachiopods, a tentacle-bearing appendage attached to the
anterior surface of the mantle cavity.
Mantle—in mollusks and brachiopods, a layer of tissue containing cells
that secrete the shell.
Meso-—a prefix signifying middle.
Mesozoic—that era of geologic time that precedes the Cenozoic and
follows the Paleozoic.
Miocene—fourth oldest epoch of the Tertiary period; follows the
Oligocene, precedes the Pliocene.
Mississippian—fifth oldest period of the Paleozoic: follows the
Devonian, precedes the Pennsylvanian.
Multicellular—composed of more than one cell.
Nacreous—pearly.
Node—a knob.
-oid—a suffix meaning “in the form of.”
Oligocene—the third oldest epoch of the Tertiary period: precedes the
Miocene, follows the Eocene.
Operculum—the lid or covering of the aperture of certain shells.
Oral—referring to the mouth or aperture.
Orbitoidids—foraminifers with large typically disk-shaped tests.
Ordovician—second oldest period of the Paleozoic era; follows the
Cambrian, precedes the Silurian.
Ossicle—loosely used as a small plate.
Paleocene—oldest epoch of the Tertiary period; precedes the Eocene.
Paleozoic—that era of geologic time that follows Precambrian time and
precedes the Mesozoic era.
Pedicle opening (pedicle foramen)—see Foramen.
Pelecypod—a bivalved aquatic invertebrate; member of class Pelecypoda,
phylum Mollusca.
Pennsylvanian—the sixth oldest period of the Paleozoic era; follows the
Mississippian, precedes the Permian.
Period—a division of geologic time (Pl. 1).
Periostracum—the horny outer covering or epidermis on shells.
Permian—seventh and last period of the Paleozoic.
Permineralization—that process by which mineral matter has been added to
the original shell material by precipitation in the interstices rather
than replacing the original shell material.
Phosphatic—containing or pertaining to phosphate minerals.
Phylum—one of the primary divisions of the animal or vegetable kingdoms.
Planispiral—shell coiled in one plane.
Pleistocene—earliest epoch of Quaternary period, Cenozoic era; follows
Pliocene epoch of Tertiary period, precedes Recent epoch of
Quaternary.
Pleural—referring to the side or ribs; in trilobites, refers to lateral
portions of thorax and pygidium.
Pliocene—latest epoch of Tertiary period of Cenozoic era; follows
Miocene epoch and precedes Pleistocene epoch of Quaternary period.
Polygonal—many sided or having many-sided plates.
Polyp—a many-tentacled aquatic coelenterate animal, typically
cylindrical or cup-shaped, as in corals.
Porcelaneous—like porcelain.
Pore—a very small opening.
Posterior—situated behind; to the rear.
Precambrian—that portion of geologic time before the Cambrian; divided
into Archeozoic era (Early Precambrian) and Proterozoic era (Late
Precambrian).
Protero—combining form meaning fore, former, or anterior in time (Greek
_proteros_, fore).
Proterozoic—youngest era of the Precambrian; follows the Archeozoic era
and precedes the Cambrian period of the Paleozoic era.
Protista—the organic kingdom including the simplest of all one-celled
organisms which possess various characters of both plants and animals;
bacteria, algae, foraminifers, radiolarians.
Protoconch—in mollusks, the initial chamber of shell.
Pyrite—a hard, brass-yellow mineral composed of iron sulfide; “fool’s
gold.”
Quaternary—the youngest period of the Cenozoic era, follows the Tertiary
period.
Radial symmetry—see Symmetry.
Reef—a mound-like or ridge-like elevation of the sea bottom which almost
reaches the surface of the water, composed primarily of organic
material and commonly formed by reef-building animals, such as corals
and oysters.
Replacement—type of fossilization whereby hard parts of organisms are
removed by solution accompanied by almost simultaneous deposition of
other substances in the resulting voids; mineralization.
Respiration—the process of oxygenation.
Rock—an aggregation of one or more minerals.
Rock-unit—divisions of rocks based on definite physical and lithologic
characteristics and not defined on the basis of geologic time alone;
groups, formations, members.
Rudistid—a Cretaceous pelecypod that does not exhibit the typical clam
or oyster shape; many are cone-shaped, resembling corals.
Saddle—in cephalopods, the forward flexure (curved toward the aperture)
of the suture or septum.
Scaphopod—an exclusively marine mollusk with a single-valved tusk-shaped
shell; member of class Scaphopoda, phylum Mollusca.
Scavenger—an animal that feeds on organic refuse.
Sedentary—stationary in life, not moving from place to place.
Sediment—material that has been deposited by settling from a
transportation agent such as water or air; typically composed of
weathered rock fragments.
Sedimentary rock—rocks formed from the accumulation and lithification of
sediments.
Segment—one of the parts into which a body naturally separates or is
divided; for example, segments of arthropods or annelid worms.
Septal—pertaining to the septum.
Septum (plural, septa)—a dividing wall or partition; in fusulinids, a
partition between chambers in the fusulinid shell; in corals, one of
the radiating, longitudinal, calcareous plates located within the
corallite; in cephalopods, the transverse partitions between the
chambers.
Series—the rocks formed during an epoch; the time-stratigraphic term
next in rank below a system.
Serrate—notched like a saw.
Sessile—animal attached to the sea floor more or less permanently.
Silica—an oxide of silicon (SiO₂).
Siliceous—containing or pertaining to silica.
Silicification—the process of combining or impregnating with silica.
Silurian—the third oldest period of the Paleozoic era; follows the
Ordovician, precedes the Devonian.
Sinus—an elongate depression on brachiopod shells.
Siphuncle—in cephalopods, the segmented horny or calcareous tube which
extends from the protoconch to the living chamber.
Slickensides—polished and grooved surfaces that are the result of two
rock masses sliding past each other as in faulting.
Solitary—living alone; not part of a colony.
Species—one of the smaller natural divisions in classification.
Specific name—see Trivial name.
Spicule—a minute spike or dart, skeletal element in sponges and
holothurians.
Stratum (plural, strata)—a single bed or layer of rock.
Strike—the direction of a real or imaginary line that is formed by the
intersection of a bed or stratum with a horizontal plane; strike is
perpendicular to the dip.
Subconical—less than conical in shape; almost a cone.
Suture—the line of junction between two parts; in crinoids, the line of
junction between two plates; in gastropods, the line of junction of
the whorls as seen on the exterior of the shell; in cephalopods, the
line of junction between a septum and the shell wall.
Symmetry—orderly arrangement of parts of an object with reference to
lines, planes, or points.
_Bilateral symmetry_—the symmetrical duplication of parts on each side
of a vertical anterior-posterior plane.
_Radial symmetry_—the symmetrical repetition of parts around a common
vertical dorso-ventrally disposed axis.
_Pentamerous symmetry_—symmetry arranged in a pattern of fives.
System—the rocks formed during a period; the time-stratigraphic term
next in rank above a series.
Taxonomy—that branch of science that deals with classification,
especially in relation to plants, animals, or fossils.
Tertiary—the oldest period of the Cenozoic era; follows the Cretaceous
period of the Mesozoic and precedes the Quaternary period of the
Cenozoic.
Test—the protective covering of some invertebrate animals.
Theca—a sheath or case; in coelenterates, the bounding wall at or near
the margin of the exoskeleton; in echinoderms, the main body skeleton
(or calyx) which houses the animal’s soft parts; in graptolites, any
cup or tube of the colony.
Thorax—in trilobites, that part of the body between the cephalon and
pygidium.
Time-unit—a portion of continuous geologic time (e.g., eras, periods,
epochs, and ages).
Time-rock unit—same as time-stratigraphic unit.
Time-stratigraphic unit—term given to rock units with boundaries
established by geologic time; strata deposited during definite
portions of geologic time (e.g., systems, series, stages, etc.).
Topography—the physical features or configuration of a land surface.
Topographic map—a map showing the physical features of an area,
especially the relief and contour of the land.
Transverse—at right angles to length.
Triassic—the youngest period of the Mesozoic era; follows the Permian
period of the Paleozoic and precedes the Jurassic period of the
Mesozoic.
Trilobite—an extinct marine arthropod having a flattened segmented body
covered by a hardened dorsal exoskeleton divided into three lobes.
Trivial name—the Latinized name added to a generic name to distinguish
the species; same as specific name.
Type locality—the geographic location at which a formation was first
described and from which it was named; or from which the type specimen
of a fossil species comes.
Type specimen—the individual or specimen on which the original
designation of a species was established.
Umbilicus—an external depression or opening at the center of many
loosely coiled shells; in gastropods it is usually located at the base
of the shell; in cephalopods it is usually located laterally.
Umbo—the arched part of the valve near the beak in bivalve shells.
Unicellular—composed of one cell.
Valve—the one or more pieces comprising the shell of animals.
Variety—a subdivision of a species, designated by a third name when a
variety is designated.
Ventral—pertaining to the abdomen; as opposed to dorsal, pertaining to
the back.
Vertebrate—an animal having a backbone or spinal column.
Whorl—a single turn or volution of a coiled shell.
-zoic—combining form meaning “life” (Greek _zoikos_, life).
Zooecium (plural, zooecia)—tube or chamber occupied by an individual of
the bryozoan colony; also called an autopore.