singular taxon shaped organic walled marine produced unknown animal common periods mid millimetre scale organisms abundant types marine sediment globe wide distribution rapid pace evolution makes valuable markers bizarre form classification ecological reconstruction difficult discovery suggestions plant fungal entertained organisms better understood improvements facilitated study fine structure mounting evidence suggest represent eggs juvenile stage marine animal ecology open speculation floated water column attached organisms species particular living conditions tend common specific abundance varied seasons appearance range length appear dark viewed optical microscope external ornamentation preserved surface fossils form hairs loops large chamber range complexity increased time backdrop decreasing organism size earliest species large smooth walled mid large expanding variety hollow evident shorter generally solid larger tend hollow largest displaying internal structure hollow leave mark inner wall organisms suggest attached outside debate number layers present organisms walls layers reported internal wall specimens appear display multitude walls reflect construction organism result process immature juvenile examples found suggest didn grow unlikely parts organism formed developmental process complete found isolated fossils chains multiple tests joined base reported genera long chains tend form spring occasionally clusters condensed chains found packed organic classification original description placed families spanning seven genera based morphological grounds genera identified annual basis time progressed publication original classification additional discoveries advances advent scanning electron microscope 1970s allowed improved detection surface ornamentation hugely important identification appreciated comparison images page light microscope image far greater quality achieved earlier century poorly preserved specimens advanced original families proposed represented best classification possible available data based largely presence absence chains organisms chamber shape orders subsequently revised conform better taxonomy placing related organisms closely possible scientific advances permitted identification distinctive traits organisms groups features base neck presence spines connections considered useful features relationships original guess order similar based tests produced extant members group chemistry tests differs fossils modern exclusively fresh water extremely different environment year abandoned initial idea arguments forwards proposed organisms plants similar grouped mentioned previously spines attached exterior vessel animals cellular machinery necessary perform feat analogy envelope found kingdom young colonial organic walled fossils occurred life cycle known clear reproduced suggested represent pre stages period colony sexual reproduction formation new colony hypothesis appears supported occurrence fossils appear mirror similar chemical composition fossils seized sides argument proponents suggest use chemical framework indicator related factor means situations favouring preservation tend preserve preparation techniques extract fossils favour groups equally apparent occurrence fossils merely artifact similar composition hypothesis struggles explain continuing abundance middle increasingly rare forms particular group suggested affiliated eggs test fixed scope parts rotate makes likely tests containers protect inside organism clutch hatching eggs arguments association impossible phenomenon laid groups fact nature chains suggest laid organism true chains attributed straight worms organisms recent excavations south_africa yielded alongside wide range organisms suggested organism created present notable absence organisms present ruled variety reasons worms cephalopods remain likely candidates evidence connecting groups best ecology immediately clear mode life occupied shaped fossils answer apparent following lines reasoning fossils restriction marine sediments taken sound evidence organisms seas presents main modes life living sediment benthic dwelling sea floor anchored place free floating water column mode life quickly ruled fossils found alignment current attached fallen water column cast light question whilst cases defensive role making vessel larger predators probable impossible anchored organisms sea floor low density construction makes unlikely plausible acted attach organisms longer spines organisms decreasing number increasing relative importance water possible long hand walls probably thick dense allow float whilst little known interactions organisms small holes tests evidence hosts parasites forms marks caused mineral cylindrical holes chamber flesh organism likely concentrated evidence biological cause daily growth markings found association abundant allow detection seasonal variation abundance peak abundance late autumn months observed different species occurring different dates pattern observed modern day tropical diversity living habits reflected depth water distance shore different species found highest abundance different depths deeper waters shoreline generally optimal environment species appear prefer shallow water abundant turbulent waters reef environments implying regimes alive effect focusing shallower water reverse necessarily true survive freshwater input application recognised named group proven incredibly useful markers periods utility morphological evolution abundance productive samples bearing thousand tests easy identification largely large variation shapes short million years species widely distributed appear variety marine settings making easier better recognised strongly rocks convergence morphological form similar environments leads mistaken identification species areas separated vast differences space time sharing similar environment clearly cause major problems organisms interpreted species aside reliable means units late 1960s detailed study fully potential
Chitinozoan