<descriptor thcode="2"><thesaurus thcode="2" name="USGS Thesaurus" scope="Topics and methods of scientific study carried out by USGS, with product types, scientific disciplines, geologic time, and types of institutional structure and activities.  Broad and shallow, used to help people find scientific information." creator="U.S. Geological Survey" rights="Public domain" edition="2.0" date="2020-01-09" codetype="number" prefix="topic" uri="https://www2.usgs.gov/science/USGSThesaurus" tblname="term" nonpref="nonpref" relterm="relterm" root_code="1" contact="pschweitzer"><category><term thcode="25" code="29" name="distinct labels" parent="26" scope="Preferred labels (descriptor texts) are distinct within the thesaurus. A concept can be specified either by its unique identifier (code) or by the text of its descriptor."/><term thcode="25" code="16" name="hierarchical" parent="11" scope="Substantive broader-narrower relationships exist among the terms."/><term thcode="25" code="13" name="transitive" parent="12" scope="Narrower terms have an &quot;is a&quot; relationship with their broader terms, and generally can be described as part-of, type-of, or instance-of the broader term."/><term thcode="25" code="21" name="disciplines" parent="2" scope="Broad categories of human inquiry or activity, such as scientific disciplines."/><term thcode="25" code="20" name="methods" parent="2" scope="Actions taken to obtain or analyze information"/><term thcode="25" code="19" name="organizational functions" parent="2" scope="Things that organizations do, typically including various types of programs, projects, and services."/><term thcode="25" code="7" name="temporal" parent="2" scope="Terms indicate periods of time, such as chronostratigraphic units, named historical periods or intervals surrounding known historical events, or seasons."/><term thcode="25" code="5" name="theme" parent="2" scope="Terms indicate domains of human concern, such as scientific discipline, societal problems, or characteristics of earth, space, oceans, and living things."/><term thcode="25" code="29" name="distinct labels" parent="26" scope="Preferred labels (descriptor texts) are distinct within the thesaurus. A concept can be specified either by its unique identifier (code) or by the text of its descriptor."/><term thcode="25" code="16" name="hierarchical" parent="11" scope="Substantive broader-narrower relationships exist among the terms."/><term thcode="25" code="13" name="transitive" parent="12" scope="Narrower terms have an &quot;is a&quot; relationship with their broader terms, and generally can be described as part-of, type-of, or instance-of the broader term."/><term thcode="25" code="21" name="disciplines" parent="2" scope="Broad categories of human inquiry or activity, such as scientific disciplines."/><term thcode="25" code="20" name="methods" parent="2" scope="Actions taken to obtain or analyze information"/><term thcode="25" code="19" name="organizational functions" parent="2" scope="Things that organizations do, typically including various types of programs, projects, and services."/><term thcode="25" code="7" name="temporal" parent="2" scope="Terms indicate periods of time, such as chronostratigraphic units, named historical periods or intervals surrounding known historical events, or seasons."/><term thcode="25" code="5" name="theme" parent="2" scope="Terms indicate domains of human concern, such as scientific discipline, societal problems, or characteristics of earth, space, oceans, and living things."/></category><altlabel><altlabel>USGSThesaurus</altlabel><altlabel>USGSThesaurus</altlabel></altlabel></thesaurus><term thcode="2" code="606" name="invertebrates" parent="45" scope="Animals having no backbone or spinal column, such as insects, mollusks, crustaceans, worms, and similar organisms."/><bt><term thcode="2" code="45" name="animals" parent="843" scope="Multi-celled organisms of the kingdom Animalia with eukaryotic cells (cells with distinct nuclei containing genetic material and bounded by thin membranes) that are heterotrophic (obtaining energy from organic substances produced by other organisms)."/><term thcode="2" code="843" name="organisms" parent="1174" scope="Living individuals that grow, reproduce, and die."/><term thcode="2" code="1174" name="topics" parent="1" scope="Themes, subjects, and concerns for which USGS information resources are relevant."/><term thcode="2" code="1" name="Categories" scope="Thematic terms for categorizing information resources.  This thesaurus is intended to support finding and understanding scientific information."/></bt><nt><term thcode="2" code="58" name="arthropods" parent="606" scope="Invertebrates belonging to the largest phylum of animals, Arthropoda, with an exoskeleton, segmented bodies, and jointed appendages, including many subphyla and classes, such as insects, crustaceans, horseshoe crabs, sea spiders, centipedes, millipedes, and the extinct trilobites."/><term thcode="2" code="130" name="bryozoans and brachiopods" parent="606" scope="Aquatic invertebrates, usually marine, belonging to the phyla Bryozoa and Brachiopoda.  Brachiopods, or clam shells, are solitary living invertebrates characterized by two shells and a lophophore, which is a complex food gathering organ.  Bryozoans are colonial and include moss coral and moss polyps."/><term thcode="2" code="177" name="coelenterates" parent="606" scope="Freshwater and marine invertebrates, such as corals, jellyfish, and sea anemones, belonging to the phylum Coelenterata and living as sedentary polyps or free swimming medusae."/><term thcode="2" code="192" name="conodonts" parent="606" scope="Microscopic teeth of primitive, boneless, eel-like animals, similar to modern hagfish, that lived in many of the world's oceans from the Cambrian through Triassic Periods of geologic time (550 to 210 million years ago)."/><term thcode="2" code="305" name="echinoderms" parent="606" scope="Marine invertebrates of the phylum Echinodermata with a radial body and a calcareous exoskeleton. Includes starfishes, brittle stars, sea lilies, sea urchins, and sea cucumbers."/><term thcode="2" code="757" name="mollusks" parent="606" scope="Invertebrates belonging to the phylum Mollusca with soft, nonsegmented bodies, often covered by a hard shell.  Includes snails, clams, oysters, whelks, mussels, slugs, octopuses, and squids."/><term thcode="2" code="1094" name="sponges" parent="606" scope="Aquatic invertebrates belonging to the phylum Porifera having internal skeletons of silica or collagen, porous body around a cavity or cavities, and usually living in stationary communities."/><term thcode="2" code="1733" name="tunicates" parent="606" scope="Marine organisms of the subphylum tunicata of the phylum chordata."/><term thcode="2" code="1336" name="worms" parent="606" scope="Invertebrate animals of the phyla Annelida, Nematoda, Memertea, or Plathyhelminthes, that have long thin rounded or flat bodies without obvious appendages."/></nt><rt><term thcode="2" code="604" name="invertebrate paleontology" parent="861" scope="Branch of paleontology which deals with fossil animals without backbones."/><term thcode="2" code="605" name="invertebrate zoology" parent="1339" scope="Branch of biology dealing with animals having no backbones or spinal columns."/></rt></descriptor>