古生代时期(Paleozoic) ，开始于前寒武纪的生物爆发(大约5亿4200万年前)，到二叠纪末期的生物大灭绝(大约2亿5100万年前)，约有3亿年之久。在古生代早期，大部分现存的生物门开始出现，在那时海底生物移居陆地。地球上目前许多自然资源的供给，如煤、石油和石灰岩，都是在古生代时期形成的。
连结网页
- The National Atlas shows where you might find various sorts of Paleozoic rocks (for those living in North America)
- University of California Berkeley has a good site about the Paleozoic.
- Palaeos also has a very fine site about the Paleozoic, thanks to M. Alan Kazlev.
- If you want to know more about the Cambrian Explosion of life, learn about the Burgess Shale fossils at this site by Andrew MacRae of the University of Calgary.
- The International Commission on Stratigraphy has a good list of the ages making up the Paleozoic at this site.