In general, the surviving taxa were rare before the extinction, suggesting that they were generalists who were poor competitors when times were easy, but prospered when specialised groups became extinct and left ecological niches vacant.
I store træk var de overlevende grupper sjældne før udslettelsen, hvad der antyder, at de var generalister, som var svage konkurrenter under milde forhold, men som trivedes, da de specialiserede grupper uddøde og efterlod tomme, økologiske nicher.