![]() Molecular data estimate the divergence time of subclasses that have recent representatives, Nautiloidea and Coleoidea and places it in the mid-Palaeozoic (cca. It is suggesed that stem cephalopods were present in the early Cambrian (541 to 485 million years ago (mya). Exactly which fossils represent stem cephalopods is still up for debate, but it is assumed that the earliest cephalopod fossil is Plectronoceras cambria (Kroger et al 2011).ĭrawing of Plectronoceras sp. Its shell probably facilitated buoyancy control, a phenomenon also seen in modern nautiloids. The main problem science of palaeontology faces regarding cephalopod evolution is deciding what is, and what is not, a cephalopod. However the fossil record remains far from complete, mainly because there are only a few recent fossils. They mature quickly and rarely live for more than two years (Mather and Kuba 2009).Ī series of truly fortunate events had to have occurred in order for an individual to become a fossil. The fossil record of early cephalopods is extremely rich as all cephs prior to coleoids had an external calcium carbonate shell (Kroger et al 2011.). The diversity among groups can be so great that it is difficult to establish which groups are most closely related (Allcock 2015). Cephalopods have adapted to occupy multiple habitats in the marine environment, from shallow shelf seas to benthic abyssal plains, from the tropics to polar regions and are the most diverse molluscs. They have well developed senses, large brains, highly evolved eyes and astonishing camouflage. Cephalopods are extraordinary molluscs and are the most intelligent and complex invertebrates. There are around 800 living cephalopod species contained in two groups: Nautiloidea which includes Nautilus and Allonautilus, and Coleoidea which includes octopuses, squid, cuttlefish and their relatives. Cephalopods, a class of marine molluscs are what scientists classify octopuses, squid, cuttlefish and nautiluses.
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