Glossary

Many geological and zoological words not explained fully in the text are described briefly. Names of animals and plants are listed in the index at the end of the book, and selected taxa are described in the Classification of Organisms.

Abyssal Relating to the ocean floor (at depths greater than about 2,000 m).

Adductor muscle In bivalves and brachiopods: a muscle used for closing the valves. Ambulacrum In echinoids: area of plates which are perforated by pores for the tube feet. Antenna In arthropods and worms: a sensory appendage.

Appendage In arthropods and worms: an organ for locomotion, feeding, feeling or breathing; usually a pair on each segment. Aptychus In ammonites: one of a pair of plates which closed the aperture. Aragonite An orthorhombic mineral form of calcium carbonate; less stable at normal temperatures and pressures than calcite. Arenaceous Applying to a sediment consisting of sand-size particles.

Argillaceous Applying to a sediment consisting of clay-size particles. An argillaceous sandstone is a muddy sandstone.

Articulate Jointed; in brachiopods: possessing teeth on the hinge where the valves open. Assemblage A group of organisms which occur together.

Association A recurring assemblage, which may be a community or part of a community. Backreef The area behind a reef (away from the open sea).

Basin An area where sediments accumulate, usually associated with contemporaneous subsidence.

Benthos Animals and plants living on the sea floor. (Adjective: benthic)

Bioherm An accumulation of organic remains on the site where the organisms lived; distinguished from other sediments by the fact that the majority of fossils have not been transported by currents, and thus bedding is often poorly developed.

Biota The fauna and flora.

Bioturbated Disturbed by burrowing animals; the bedding planes of many bioturbated sediments are convoluted or obscured. Bituminous Containing bitumen (hydrocarbons) or other carbonaceous matter. Body fossil The fossil remains of an organism (as opposed to a trace, trail or imprint). Boreal The northern parts of the Earth. Botryoidal In the form of a bunch of grapes. Brachial valve In brachiopods: the valve containing the support for the lophophore (the brachial skeleton).

Byssus In bivalves: horny threads for attachment to the sea floor or other anchorage. Calcarenite A limestone composed of sand-sized particles, usually shell fragments. Calcareous Made of, or rich in, calcium carbonate.

Calcilutite A limestone consisting of clay-size particles; often thought to be of algal origin. (Synonyms: micrite, calcite mudstone) Calcisphere A microscopic hollow calcareous sphere; these spheres are important rock formers of uncertain biological affinities, though probably algal.

Calcite A hexagonal mineral form of calcium carbonate; usually more stable than aragonite. Carapace In arthropods: the dorsal covering. Carbonate A compound • containing the CO3 ion; calcium carbonate (CaCOa) is the most abundant carbonate in marine environments. Carbonate sediments usually consist of the calcareous skeletons ot marine organisms. Carbonate mudstone Synonymous with calcil-utite and micrite.

Carnivore An animal which feeds on other animals.

Cartilage Elastic tissue (gristle) present in most vertebrates.

Cast The replacement of a fossil by some other material.

Cephalon In trilobites: the head-shield. Chamosite A dark mineral, related to chlorite, which is common in many sedimentary iron ores.

Chert Cryptocrystalline silica; a silicous rock often composed of radiolaria.

Chitin A tough organic compound. It can combine with other substances to form a large variety of materials, e.g. the chitino-phosphatic shells of some inarticulate brachiopods. Class A major division of a phylum. Clastic Relating to sediments composed of rock fragments (e.g. conglomerate, sand, silt) or clay minerals.

Clay A fine grained sediment composed mostly of clay minerals (hydrous aliminium silicates) and other material less than 4 microns in diameter.

Community A group of organisms living in the same habitat (at the same time, and in the same area). In palaeontology, the word is normally used for the part of the community which is preserved (as body fossils or as trace fossils). Concretion A mass of more resistant material precipitated in a rock, usually a concentration (round a nucleus, which may often be a fossil) of some compound already present in the rock (e.g. calcareous concretions in a clay; flints in chalk).

Conglomerate A sedimentary rock composed of rounded fragments that are normally greater than 2 mm in diameter, set in a fine grained matrix.

Coquina A deposit of drifted shells. Cracker A term for a large calcareous concretion in a sandstone, applied in particular to concretions in some Mesozoic sandstones in the south of England.

Cross-bedding Inclined bedding planes within a thicker bedded unit, which reflect deposition on a sloping surface.

Cusp In vertebrates: a projection on a tooth. Deltaic sequence Sediments laid down in the vicinity of a delta, which characteristically show coarsening upward changes in grain size over several metres or tens of metres (as the delta front advances).

Dental plates In brachiopods: a pair of plates near the umbo which extend from the teeth to the floor of the pedicle valve.

Deposit feeder An alternative term for detritus feeder.

Detritus feeder An animal which feeds on organic matter coating grains of sediment or mixed with the sediment.

Dextral On the right (as opposed to sinistral). Diagenesis Alterations to a sediment after initial deposition.

Diversity The number of species present in an assemblage.

Dorsal Strictly speaking, relating to the top of an animal, but in some invertebrates the dorsal direction is conventional (e.g. in bivalves, the hinge line is always taken to be on the dorsal side).

Ecogroup Successive communities in a similar habitat.

Ecology The study of the relations between organisms and their environments. Epeiric sea A sea on the continental shelf or covering part of a continent.

Epifauna Animals living on the surface of the sea floor.

Epiplankton Organisms living attached to larger plankton or to floating objects (e.g. driftwood).

Epizoan An organism living attached to another organism.

Euryhaline Relating to animals which can tolerate a broad range of salinity. Eustatic Relating to world-wide changes in sea level.

Facies A term applied to rocks or fossils (e.g. sandy facies, shelly facies) to indicate an association of lithological and/or palaeontological characteristics.

Family A group of genera with common ancestry.

Fauna The animals present in an area at a particular time.

F'aunal province A large area of the world, containing numerous communities, which is isolated from other faunal provinces by some (complete or partial) barrier to migration, Filament An elongate or thread-like arrangement of cells of organs.

Filter feeder An animal which extracts organic matter suspended in sea water by setting up a current through a feeding organ, which filters out the food required.

Flagellum A thread-like structure used to set up water currents in some invertebrates.

Flint Black chert, common as nodules in the

Chalk of southern England.

Fluviatile Relating to a river.

Forereef The area on the seaward side of a reef.

Fossil The skeleton, impression or trace of an organism preserved in a rock. Trace fossils (burrows, trails, etc.) are classified separately from body fossils (shells, bones, etc.). Functional morphology The interpretation of the function of an organism by reference to its shape.

Genal spine In trilobites: a spine extending backwards from the side of the cephalon. Genus A group of closely related species (plural: genera).

Glabella In trilobites: the axial region of the cephalon.

Glauconite A green iron silicate, common in many shallow marine sands (e.g. the Upper Greensand of southern England). Gondwanaland The large Palaeozoic continent consisting of South America, Africa, India, Australia and Antarctica.

Graben An elongate depression bounded by faults.

Guard In belemnites: the solid calcite counterweight.

Habitat The space in which a community lives. Hardground A cemented surface exposed on the sea floor, particularly common in some shallow water carbonate sequences. Herbivore An animal which feeds mainly on plant material.

Hermatypic In corals: a form which depends on the presence of microscopic algae in its tissues.

Heteromorph In ammonites: a form in which the coiling is not a regular plane spiral. Hinge line In bivalves and brachiopods: a line (passing through the teeth and sockets) about which the two valves articulate. Iapetus Ocean An ocean which extended from Norway to Connecticut during Lower Palaeozoic time, and which did not finally close until the Devonian.

Inarticulate In brachiopods: a primitive class with no teeth.

Infauna Animals which live within the sediment on the sea floor.

Interarea In brachiopods: that part of the pedicle valve between the umbo and the hinge line. Invertebrate An animal without a bony or cartilaginous internal skeleton.

Ironstone A sedimentary rock rich in iron minerals.

Island arc A chain of islands (predominantly volcanic) which occurs above a region where ocean floor material is descending below the Earth's crust.

Kingdom One of the three largest divisions of organisms, viz. protists, plants and animals. Lag deposit A residual accumulation of coarser particles left after the finer material has been removed by currents.

Lamina The thinnest recognizable unit in a bedded sediment.

Larva The earliest growth stage of many invertebrates; the larvae of many bottom dwelling invertebrates are pelagic.

Ligament In bivalves: an elastic substance which opens the valves when the adductor muscles are relaxed.

Limestone A rock composed of calcium carbonate, usually the skeletons of marine organisms.

Limonite Hydrous iron oxide, usually the result of weathering of other iron compounds. Lithification The chemical and physical processes which convert an unconsolidated sediment into a solid rock.

Lithology The physical character of a rock. Lophophore An organ with tentacles which sets up currents for feeding and respiration. Lumachelle An accumulation of shells in a sediment.

Magnetic stripes Areas of oceanic floor which have alternatively reversed magnetic polarity, and which are symmetrical about a mid-ocean spreading centre.

Mantle Fleshy tissue which lines the shell of some invertebrates, and from which additions to the shell are secreted. (Also: that part of the Earth which lies below the crust and outside the core)

Massif An area which subsides less than the surrounding areas, and where sediments (of a particular time interval) are either thin or absent. Mesentery In corals: a radial fleshy structure situated between adjacent septa. Micrite A limestone composed of clay-size particles (calcilutite).

Mould The cavity or impression left after removal of a fossil by solution.

Muscle scars Marks on the interior of a shell where muscles were attached. Nekton Swimming animals.

Niche The habitat and ecological setting of an organism.

Nodule A concretion.

Notochord In chordates: a cylindrical sheath forming a flexible support for the back. Oncolite A concentrically layered calcareous structure formed by blue-green algae. Oolite A rock composed of ooliths. The small spheres resemble a fish roe (hence the name). Oolith A small sphere built up of concentric layers (usually calcium carbonate) due to successive episodes of inorganic precipitation around a nucleus (often a shell fragment). Operculum A lid covering the aperture of some shelled invertebrates.

Order A group of families with certain characters in common, which suggest that they are related.

Organism A plant, an animal, or a protist. Ornament Ribs, tubercles, or other irregularities on the surface of a shell. In spite of the name, ornament probably always has some function.

Orogeny The formation of mountains, usually accompanied by deformation of the rocks in the region concerned.

Pangea The Permian continent formed from the fusion of all the large continental masses on the Earth.

Pedicle A stalk, developed in various invertebrate epifauna for support.

Pedicle opening In brachiopods: the opening in the larger (pedicle) valve through which the pedicle emerges.

Pelagic Relating to organisms which are free-swimming or floating.

Period The time during which the rocks of a stratigraphical system were formed, e.g. the Jurassic Period was the time when rocks of the Jurassic System were formed.

Phanerozoic The eon comprising the Palaeozoic, the Mesozoic and the Cenozoic eras. Photosynthesis The formation of carbohydrates from water and carbon dioxide in tissues exposed to light; the method normally employed in plants.

Phragmacone In cephalopods: the chambered shell; in belemnites, this is the conical shell which fits into the front end of the guard. Phylum A major subdivision of a kingdom (plural: phyla).

Phytoplankton Plankton which employ photosynthesis.

Plankton Floating organisms; much of the plankton consists of minute protists and invertebrate larvae.

Plant A multi-cellular organism normally subsisting by photosynthesis.

Population The members of a species in a defined area.

Process An organ, part of an organ, or part of the skeleton which projects outwards from the principal surface.

Protein A group of complex carbohydrates; some proteins form soft fleshy matter, while others form hard substances.

Protista The kingdom which includes most single-celled organisms.

Radula In gastropods and some other molluscs: an organ bearing rasp-like teeth used in scraping, tearing or boring for food.

Realm A large area of the world with characteristic faunas.

Reef Either a bioherm (q.v.) or a ridge of hard rock.

Regression The retreat of the sea from a land area.

Rib A raised ridge on a shell.

Rostral spine A spine projecting forwards from the head.

Sabkha A flat coastal area subject to occasional inundation.

Salt plug A structure resulting from the upward movement of a salt mass. Sand A sediment containing grains between 0.06 and 2 mm in diameter. Most sands contain quartz grains, but the grains can be of any mineral.

Scavenger An animal which feeds on the dead remains of other animals.

Sediment Solid material that has been transported and deposited, or material that has been precipitated from water. Most sediments have been transported by water, air or ice, but some result from mass flow.

Septum A plate or partition within the skeleton. In corals: a vertical radial plate. In cephalo-pods: a plate separating the internal chambers. (Plural: septa).

Series A major division of a stratigraphical system.

Shale An indurated fissile rock consisting mostly of clay grade minerals. Siderite A rhombohedral form of iron carbonate.

Silt A sediment containing grains between 4 and 60 microns in diameter.

Sinistrally coiled Coiled in a left-handed manner. In gastropods: those forms which, when the spire is upwards and the aperture opening towards the observer, have the aperture on the left (most gastropods have the aperture on the right, i.e. they are coiled dextrally). Siphon A tubular organ for conveying water. In bivalves it consists of two tubes (like a double-barrelled shotgun), one for the water going in, and one for the water going out. Siphuncle In cephalopods: a tube extending to the apex of the shell, which passes through openings in the septa.

Slump A mass of sediment which has slid down a slope.

Species A group of organisms which can interbreed and produce fertile offspring. In fossils, members of the same species can only be deduced from morphological gradations between variants.

Spondylium In brachiopods: internal plates in the pedicle valve of pentamerids and some other groups.

Spreite Sedimentary laminations between the arms of a 'U'-shaped burrow.

Stage A biostratigraphical subdivision of a system, commonly based on a succession of biostratigraphical zones.

Stenohaline Relating to animals which can only tolerate a narrow range of salinity; most steno-haline animals are confined to the open sea. Stolon A tube.

Substrate The sediment or rock surface on the sea floor.

Sulcate In brachiopods: with a folded anterior margin. In ammonites: with a ventral groove. Suspension feeder An animal which feeds on organic matter suspended in sea water. Most suspension feeders are filter feeders. Suture A line. In cephalopods: the line where a septum joins the outer shell. In trilobites: the facial suture is the line on the dorsal head-shield (cephalon) along which the carapace split prior to the animal's moulting. Swell An area which, over a period of time, subsides less than the surrounding areas, and is thus covered by thinner sedimentary sequences. Symbiotic Relating to different organisms which live in close association with each other. System The rocks formed during a geological period.

Tabula A more or less horizontal plate extending across the interior of a coral, (plural: tabulae).

Tax on A classification unit in biology, e.g. species, genus, family, order, (plural: taxa). Tectonic Relating to geological structures. Telson In arthropods: a posterior plate or spine.

Terrigenous Derived from the land.

Tethys An ocean which, during the Mesozoic, lay to the south of Europe and much of Asia, and to the north of Africa and India. Theca A cup-like structure in many animals. Thixotropic clay A clay which becomes weaker when disturbed and more coherent when left undisturbed.

Thorax In arthropods: the part of the body between the head and the tail, usually with well marked segments.

Tillite A lithified boulder clay, deposited by ice.

Tooth In bivalves and brachiopods: a projection on the hinge line which fits into a socket in the opposite valve, and thus serves to prevent slippage between the valves.

Trace fossil A sedimentary structure resulting from the activity of an animal (e.g. burrow, trail, bore).

Transgression The spread of the sea over a land area.

Trophic Relating to the food chain in animals. Turbidite A sediment deposited by a turbidity current; the lower part of each bed usually grades up into a mud.

Turbidity current A turbid current with a high density due to suspended rock fragments. Umbilicus That part of a planispiral shell within the outermost whorl.

Umbo In shells which grow by marginal accretion: the point where shell growth starts, (plural: umbones).

Valve A single part of an invertebrate skeleton; usually external.

Venter The ventral part of an animal. In cepha-lopods: the outer part of each whorl. Ventral Strictly speaking relating to the underside of an animal, but in some invertebrates the ventral side is conventional (e.g. in brachiopods, the pedicle valve is always considered to be ventral).

Viviparous Giving birth to living young (as opposed to laying eggs).

Zone In geography and ecology: a region with some distinctive features. In stratigraphy: the rocks deposited during an interval of time which can be recognized by characteristic fossils.

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