marine habitats ideal for spawning new life-forms. Nevertheless, the scale of the Cambrian Explosion is likely exaggerated due to the proliferation of hard-bodied animals that fossilized much more ...

Others propose that an extinction of life just before the Cambrian opened up ecological roles, or "adaptive space," that the new forms exploited. External, ecological factors like these were ...

Although these new life-forms spread worldwide ... betta fish owes its body construction to early chordates in the Cambrian such as Pikaia gracilens (the fossil shown here).