parent_taxon paciphacops
Trilobites ( meaning " three lobes ") are a fossil group of extinct marine arthropods that form the class ___MASK43___ . Trilobites form one of the earliest known groups of arthropods . The first appearance of trilobites in the fossil record defines the base of the Atdabanian stage of the Early Cambrian period , and they flourished throughout the lower Paleozoic era before beginning a drawn - out decline to extinction when , during the Devonian , all trilobite orders except the Proetids died out . Trilobites finally disappeared in the mass extinction at the end of the Permian about . The trilobites were among the most successful of all early animals , roaming the oceans for over 270 million years . The Devonian is a geologic period and system of the Paleozoic , spanning 60 million years from the end of the Silurian , million years ago ( ___MASK50___ ), to the beginning of the Carboniferous , ___MASK50___ . It is named after Devon , England , where rocks from this period were first studied . The first significant adaptive radiation of life on dry land occurred during the Devonian . Free - sporing vascular plants began to spread across dry land , forming extensive forests which covered the continents . By the middle of the Devonian , several groups of plants had evolved leaves and true roots , and by the end of the period the first seed - bearing plants appeared . Various terrestrial arthropods also became well - established . Fish reached substantial diversity during this time , leading the Devonian to often be dubbed the " Age of Fish ". The first ray - finned and lobe - finned bony fish appeared , while the placodermi began dominating almost every known aquatic environment . Paciphacops is a genus of trilobites from the order ___MASK67___ , suborder Phacopina . This genus is easily mistaken for the more common and popular genus Phacops and Kainops . It takes a careful eye to spot the difference . One major difference between Paciphacops and Phacops is that the central raised area ( or glabella ) of the headshield ( or cephalon ) extends beyond its anterior margin . The difference between Paciphacops and Kainops is that Kainops has more eye facets than Paciphacops . The skin ( or sclera ) is thickened and bulges compared to the edge of each lens . This genus can be found primarily in the United States and Australia . Some Known Species and Locations . Paciphacops birdsongensis , Tennessee . Paciphacops campbelli , Oklahoma . Paciphacops claviger , Nevada . Paciphacops logani , Oklahoma . Paciphacops crosslei , Australia . Paciphacops latigenalis , Australia . ___MASK41___ is a genus of trilobite in the order ___MASK67___ , family ___MASK70___ , that lived in Europe , northwestern Africa , North America and China from the early until the very end of the Devonian . It was a rounded animal , with a globose head and large eyes , and probably fed on detritus . " ___MASK41___ " is often found rolled up , a biological defense mechanism that is widespread among smaller trilobites but further perfected in this genus . The Cambrian Period ( or ) was the first geological period of the Paleozoic Era , of the Phanerozoic Eon . The Cambrian lasted 55 . 6 million years from the end of the preceding Ediacaran Period 541 million years ago ( ___MASK50___ ) to the beginning of the Ordovician Period ___MASK50___ . Its subdivisions , and its base , are somewhat in flux . The period was established ( as  Cambrian series ) by Adam Sedgwick , who named it after Cambria , the Latinised form of " Cymru ", the Welsh name for Wales , where Britain ' s Cambrian rocks are best exposed . The Cambrian is unique in its unusually high proportion of lagerstätte sedimentary deposits , sites of exceptional preservation where " soft " parts of organisms are preserved as well as their more resistant shells . As a result , our understanding of the Cambrian biology surpasses that of some later periods . ___MASK67___ (" Lens - face ") is an order of trilobite that lived from the Late Cambrian to the Late Devonian . It is made up of a morphologically diverse group of related suborders . Kainops is a genus of trilobites from the family ___MASK70___ , order Phacopida . It can be distinguished from " Paciphacops " by the greater number of facets to the eye ( 6  8 per row , compared to 3  4 in " Paciphacops "). The form of the furrow between the palpebral area and the palpebral lobe also distinguishes " Kainops " from the genera " Paciphacops " and " Viaphacops ". ___MASK70___ is a family of phacophid trilobites that ranges from the Lower Ordovician to the Upper Devonian , with representatives in all paleocontinents . In biology , detritus is dead particulate organic material ( as opposed to dissolved organic material ). It typically includes the bodies or fragments of dead organisms as well as fecal material . Detritus is typically colonized by communities of microorganisms which act to decompose ( or remineralize ) the material . In terrestrial ecosystems , it is encountered as leaf litter and other organic matter intermixed with soil , which is referred to as humus . Detritus of aquatic ecosystems is organic material suspended in water and piles up on seabed floors which is referred to as marine snow . Theory . Dead plants or animals , material derived from ___MASK62___ tissues ( such as skin cast off during moulting et cetera ) gradually lose their form , due to both physical processes and the action of decomposers , including grazers , ___MASK32___ and fungi . Decomposition , the process through which organic matter is decomposed , takes place in many stages . Materials like proteins , lipids and sugars with low molecular weight are rapidly consumed and absorbed by micro - organisms and organisms that feed on dead matter . Other compounds , such as complex carbohydrates are broken down more slowly . The various micro - organisms involved in the decomposition break down the organic materials in order to gain the resources they require for their own survival and proliferation . Accordingly , at the same time that the materials of plants and animals are being broken down , the materials ( biomass ) making up the bodies of the micro - organisms are built up by a process of assimilation . When micro - organisms die , fine organic particles are produced , and if these are eaten by small animals which feed on micro - organisms , they will collect inside the intestine , and change shape into large pellets of dung . As a result of this process , most of the materials from dead organisms disappears from view and is not obviously present in any recognisable form , but is in fact present in the form of a combination of fine organic particles and the organisms using them as nutrients . This combination is detritus .