# What periods of the fossil record are most lacking in specimens?

What parts of the fossil record are most lacking in specimens? That is, if you were to trace the evolution of a modern mammal (humans, for example) from abiogenesis to now, which periods are the most lacking in fossils? Where are the biggest gaps in our evolutionary history.

• Remember that you need to distinguish the types of fossils. For example, I don't think that someone is missing forams from the Cretaceous, but on the other hand some land mammals from the same period might be quite scarce. – Gimelist Nov 4 '14 at 9:48
• @Michael: I would have though "if you were to trace the evolution of a modern mammal (humans, for example) from abiogenesis to now" would have narrowed that down enough. – naught101 Nov 5 '14 at 3:32

• @John Indeed, that's what I meant by because of the paucity of pre-Ediacarian formations. – plannapus Feb 19 '18 at 8:42