genus known rocks period like organism fed surface manner similar affinity group contentious specimens found australia recent research concentrated numerous finds near russia cover interval time million years ago fossils time evolutionary relationships organisms debated initially classified type features anatomy association scratch marks resembling interpreted signs dispute classification generally accepted classification important scientific understanding explosion diverged significantly million years ago age indicate animals start etymology genus named student teacher collector lost life expedition originally described drew attention fact preoccupied woods turtle subgenus accordingly new proposed occurrence found hills south_australia formation region russia fossils associated animals trace fossil trails possibly algae beds succession dated million years ago million years ago dating lead found volcanic ash layers layers contain fossils fossils known beds older younger precisely dated range fossils dated precisely description specimens representing organisms stages maturity found area fine sandstone layers large number specimens small grain size sediments variety circumstances specimens preserved provide detailed information external form internal anatomy feeding style fossils oval outline elongated specimens illustrate organism capable stretching anterior posterior direction factor type symmetry visible specimens sign kinds radial symmetry normal group includes sea australian fossils originally described type inconsistent symmetry fossils fossils surrounding sediments lived surface sea floor dorsal described non shell larger specimens reached length width high smallest specimens long shell stiff flexible appears non tougher grew larger presumably thicker mature specimens observed elongated folded specimens illustrates shell highly single consisted highest point hood like structure forming thought specimens inner surface shell bears stripes spanning width creature represent attachment sites muscles similar stripes edge shell connected muscles involved muscular foot shell long axis organism marked raised ridge middle axis slightly body visible series repeated module included developed band ventral muscles running single broad muscular foot smaller transverse ventral muscles underside body combination bands ventral transverse ventral muscles enabled making foot body fringe animal respiratory system performing function similar gills fact fringe extended shell indicate gills inefficient needed large area effective predators shell main function provide platform muscles ecology shallow waters tens meters depth sharing calm sea floor organisms bearing bear fossils suggesting lived alongside organisms probably selective predatory habit ruled ate moved backwards trail created destroyed subsequent grazing activity conversely claim moved forwards fans grooves found head end organism indicate organism stayed place surface mat extension head bore teeth reconstruct having long neck operated like arm rotating axis perpendicular sea floor order produce sweep fan rotating away animal food substrate mouth lack evidence contrary suggests organisms reproduced sexually waters occasionally disturbed sandy currents caused sediments storms discharge washed creatures response stress organisms appear retracted soft parts shells apparently fast currents organisms survived current attempted sand deposited unsuccessful attempts seen juveniles end centimetres long preservation fossils generally preserved clay rich bed beneath sandy bed fossils preserved depressions bases beds implying organism firm resist crushed sediment accumulated soft parts organism decayed soft underneath shell preserving shape organism preservation specimens possible fast quickly cut organism enhanced decay products rotting organism helped sediment suggested trail produced organism assisted preservation experiments suggest easily play role binding sediment classification fossils found far assigned species specimens discovered australia originally classified box wade view remained popular fossils white sea region discovered prompted research specimens initially led recognised oldest documented organism far fossils sign toothed tongue feature modern excluding rarely preserved fossil absence necessarily mean rocks immediate vicinity fossils bear scratch marks compared traces named interpreted evidence presence conjunction shell taken indicate closely related suggested feeding mechanism retractable hook like organs end feeding apparatus appears differ significantly typical demonstrates best stem group notably scratch marks indicate teeth dragged organism pushed away maximum impact sediment organism direction grazing backwards opposed forwards furthermore constant width grooves implies trait derived argued shape feeding traces incompatible despite body form lack places outside crown group points plenty groups organisms bear structures capable making similar marks taken doubt available evidence reliably identify near suggest possible probable theoretical importance explosion apparently rapid increase variety basic body structures animals early period starting million years ago finishing million years ago early fossils known mid-19th century saw apparently sudden appearance animals main objections theory evolution natural selection majority animals complex split groups like features strongly suggest member means split time appeared million years ago start million years ago widely accepted member inclusive clade fossils modern looking found diverged million years ago
Kimberella