Catastrophes and Prehistory

According to a Fossil Cephalopods FAQ by Neale Monks:

"... Cephalopods ... evolved from primitive molluscs during the Late Cambrian, approximately 500 million years ago. Unlike the other molluscan groups, cephalopod evolution has concentrated not on a energetically connservative, defensive lifestyle but on mobility, dynamism, and intelligence. ...
... Cephalopods today are divided into the nautiluses, which reproduces many times, and the coleoids which reproduce only once (usually) ... The basic fact is that no ammonites are known beyond the end of the Cretaceous, while the other cephalopod groups, the coleoids and nautiloids, survive to the present day. This has been tied with other extinctions which occurred at the end of the Cretaceous (known as the Cretaceous-Tertiary, or K/T, boundary). ... How the squids and octopuses, which lived in the Mesozoic seas along with the ammonites, belemnites and nautiloids, survived is unclear. ...".

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A Comet-Earth collision about 250 million years ago caused the Permo-Triassic Extinction.

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A Mars-sized body colliding with Earth formed the Moon about 4,400 million years ago, perhaps leaving the Pacific Ocean as an impact crater and possibly forming the initial continental crust of the Earth.

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http://www.valdostamuseum.org/hamsmith/EarthCollisions.html