What usually causes a fossil to appear cleanly split into two halves across a bedding plane after excavation?

Answer

The rock matrix fractured along a plane of weakness, often the boundary between the fossil and the surrounding sediment.

The break occurs in the surrounding rock, typically along the path of least resistance, which is frequently the interface where the fossil meets the sediment, sometimes creating mirror images if the break happens during fossilization.

What usually causes a fossil to appear cleanly split into two halves across a bedding plane after excavation?
Geologyrockfossilpreservationlayer