Sphaerobolus stellatus (Cannon-ball Fungus)

When immature the whole fruiting body is a closed sphere. At maturity the outer covering splits radially, from the apex of the sphere, leading to the creation of a toothed cup, more-or-less hemispherical in shape. The number of teeth varies between four and eight. Each cup is about 2 millimetres in diameter and consists of a firm outer case and an inner membrane, that is attached to the outer cup at the tips of the teeth mentioned above. When the cup opens, there is a single red-brown ‘egg’ (or, to be technical, peridiole), about a millimetre in diameter, that sits in a bath of fluid atop the inner membrane.  Within the peridiole are the spores. The inner membrane is thin but relatively stiff whereas the main body of the cup is firm. Initially the inner membrane is curved downwards (hence cup-like) but eventually suddenly reverses its orientation end up curved upwards (hence somewhat blister-like) and in that sudden change flicks the peridiole several metres into the air, thereby dispersing the mass of spores.

You will find a description of the process in the lower half of this web page: https://www.anbg.gov.au/fungi/birds-nest-cannonball.html

The is a cosmopolitan species and is found on well-decomposed wood or herbivore dung in a variety of habitats. In urban areas in many parts of the world garden beds mulched with woodchips are a common haunt of this fungus.        

Look-alikes

There is nothing else like it.