Cephalopods (octopuses, squids, nautilus, etc.) are among the most complex invertebrates. They have been around since before the dinosaurs. Yet, there are none that tolerate fresh water today - perhaps there never have been (I am aware there is one squid in Chesapeake that lives in brackish water). This leads me to wonder about a few things:
- What is it about this class of molluscs that prevents them from exploiting fresh water environments?
- Is this why they also have not given rise to any land forms?
- Is tolerance of fresh water essential to evolution to living on the land?
- Were the predecessors (e.g. tiktaalik) of the first land vertebrates, fresh water animals?