The, possibly mythical, "fourth orifice" that porn technicians are searching for in an attempt to produce increasingly more gratuitous visual stimulus for self pleasure.
It is rumoured to have been discovered by accident during a filmed attempt at TVTA. Believed to be located towards the base of the spine, referred to colloquially as the Spange, it may in fact be the cleft form by a pair of fulsome buttocks.
The round part of the "spinejoints" or for some prefer calling them " vertebral" on animals.
There are 5 types of animals that have spines or vertebral:Mammals, reptiles, birds, fish and amphibians