• green algae (plants) with a siliceous shell – diatoms are the main primary producers in the world’s oceans
• can be found as isolated specimens or as a “chain”
• a mainly planktonic mode of life within the photic zone
• geologic range: Jurassic?/Cretaceous – Recent
• inhabit a range of aqueous environments from fresh water to fully marine
• biostratigraphically significant in particular areas/intervals but subordinate to other fossil groups and therefore has relatively few practicing specialists

Assorted diatom specimens. The diatom shell (“frustrule”) is commonly preserved in the fossil record as pyritised internal moulds.