The fossil sequence of these foraminifera stretched from just over to 10 million years ago until about the present day. For the first 4-5 million years the shells varied slightly in size and thickness but with no
The upper wheel has a few large facets. As it rolls forward it stays for a long period on each facet – a period of evolutionary stasis or equilibrium. The wheel then abruptly turns to the next facet. This represents a “punctuation event” – the rapid flip from one species to another with many differences evident between the two forms.