A principle of evolution: 'If it ain't bust, don't fix it!'

Bargain of the week! Linda and I occasionally walk around a couple of Sunday carboots in Norwich: today I bought this beautiful fossil Nautilus at one of them for £1. Nautiluses (or Nautili, depending on which sort of secondary school you attended!) are cephalopods: 'head-footed' molluscs, like octopuses, squids and the familiar prehistoric ammonites. Unlike ammonites they didn't die out at the end of the Cretaceous period: there are still a few species hanging on in tropical oceans. The photos below show the fossil and the shell of a Pacific Chambered Nautilus: they are remarkably similar!