Pseudotail

A number of species, however, have a pseudotail consisting of a few postcloacal vertebrae, but annulation is incomplete and a terminal shield is consistently present.

The spermatozoon of Saduria entomon is long and bent, resembling a whip. It consists of a very long pseudotail (1.86 mm long), which lacks an axoneme, and an extended head (112 pm long) that hangs down at an acute angle,” scientists in Poznan, Poland report.

A true human tail (persistent vestigial tail) is rare and is differentiated from a pseudotail and an acrochordon by the presence of a central core of mature fatty tissue, small blood vessels, bundles of muscle fibers, and nerve fibers.