taillessness

Taillessness is the absence of a tail or tail-like appendage. In vertebrates, a tail is a posterior extension of the spine that can aid in balance, locomotion, or communication. Taillessness can occur naturally in some species, arise through mutation or selective breeding in domesticated animals, or be encountered as a rare human congenital condition.

In animals, taillessness is most often the result of hereditary mutations or selective breeding. Domestic cats such as the Manx, and various bob-tailed dog breeds, exhibit shortened or absent tails due to genetic variation. In wild species, true taillessness is comparatively uncommon but can occur through evolutionary processes where tails become less advantageous for a given locomotor or environmental context. Evolutionary loss of tails has occurred in several primate lineages, including humans, where the external tail is absent in adults.

In humans, taillessness refers to the absence of an external tail. All humans develop a transient embryonic tail that normally regresses during the first two months of gestation, leaving only the coccyx as a bone remnant. Rare congenital conditions may present as vestigial tails, which are soft tissue protrusions containing fat, connective tissue, and sometimes connective tissue strands or cartilage; true tails, if present, are exceedingly uncommon and may include skeletal elements. Pseudo-tails are protrusions arising from other spinal or soft-tissue abnormalities.

Medical management of a vestigial tail typically involves observation or surgical removal if symptomatic or cosmetically concerning. Taillessness in humans is not considered a disability in itself but may warrant evaluation to rule out associated spinal anomalies.