WHENDIDINVERTEBRATESAPPEAR?

Invertebratesappearedbetween543and488millionyearsago.Theywereso;-bodyanimalswithashell.However,thereare665millionyearoldfossilsintheWesternCentralFlinders,Australia.Somepaleontologistssaythattheseanimalsappearedmuchearlier,possibly1billionyearsago.Theyhavenovertebralcolumn.Someexamplesareinsects,crabs,lobsters,snails,octopuses,starfish,sea-urchinsandearthworms.Aboutthe97%ofallanimalsareinvertebrates.Theword“invertebrate”comesfromthelaPnwordvertebra,thatmeansjoint.Vertebraisderivedfromverto,anotherwordinlaPnwhichcomesfromtheconceptofturning.Italsocontainstheprefix–inwhichmeans“without”.So,completely,theword“invertebrate”means“novertebra”.Thelargestgroupofinvertebratesareinsects(arthropods)whichappearedbetween410and400millionyearsago,around100millionyearsmorethantheappearanceofinvertebrates.Thereareexactly1,305,075insectspecies.