Obviously such experiments are not possible with specimens of extinct organisms found in paleontological contexts.

As it is based on living organisms, it accommodates extinct organisms poorly, if at all.

Praecambridium sigillum is an extinct organism that superficially resembles a segmented trilobite-like arthropod, though most experts place it within the Proarticulata.

They serve a valuable purpose in paleontology because they provide direct evidence of the predation and diet of extinct organisms.

All of these biological disciplines can be involved with extinct and extant organisms.

Biosphere: Marciana - All living or extinct organisms whose lineages developed on Mars.

The extinct organisms could then be observed in the fossil record, and their replacements were considered to be immutable.

When looking back at extinct organisms, there are some groups of organisms (or lineages) that have gaps in their fossil records.

Perhaps long extinct, but living organisms once existed on Mercury!

It also allows insights into the biology and ecology of extinct organisms.