Tail

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A white-tailed deer's tail White-tailed deer, tail up.jpg
A white-tailed deer's tail

The tail is the section at the rear end of certain kinds of animals' bodies; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammals, reptiles, and birds. While tails are primarily a feature of vertebrates, some invertebrates including scorpions and springtails, as well as snails and slugs, have tail-like appendages that are sometimes referred to as tails. Tailed objects are sometimes referred to as "caudate" and the part of the body associated with or proximal to the tail are given the adjective "caudal".

Contents

Function

Vulpes lagopus (Arctic fox) sleeping with its tail wrapped as a blanket. Alopex lagopus IMG 9019.JPG
Vulpes lagopus (Arctic fox) sleeping with its tail wrapped as a blanket.

Animal tails are used in a variety of ways. They provide a source of locomotion for fish and some other forms of marine life. [1] Many land animals use their tails to brush away flies and other biting insects. [2] Most canines use their tails to communicate mood and intention. [3] Some species, including cats and kangaroos, use their tails for balance; [4] [5] and some, such as monkeys and opossums, have what are known as prehensile tails, which are adapted to allow them to grasp tree branches. [6]

Tails are also used for social signaling. Some deer species flash the white underside of their tails to warn other nearby deer of possible danger, [7] beavers slap the water with their tails to indicate danger, [8] and canids (including domestic dogs) indicate emotions through the positioning and movement of their tails. [9] Some species' tails are armored, and some, such as those of scorpions, contain venom. [10]

Some species of lizard can detach ("cast") their tails from their bodies. This can help them to escape predators, which are either distracted by the wriggling, detached tail or left with only the tail while the lizard flees. Tails cast in this manner generally grow back over time, though the replacement is typically darker in colour than the original and contains only cartilage, not bone. [11] Various species of rat demonstrate a similar function with their tails, known as degloving, in which the outer layer is shed in order for the animal to escape from a predator. [12]

Most birds' tails end in long feathers called rectrices. These feathers are used as a rudder, helping the bird steer and maneuver in flight; they also help the bird to balance while it is perched. [13] In some speciessuch as birds of paradise, lyrebirds, and most notably peafowl modified tail feathers play an important role in courtship displays. [14] The extra-stiff tail feathers of other species, including woodpeckers and woodcreepers, allow them to brace themselves firmly against tree trunks. [15]

The tails of grazing animals, such as horses, are used both to sweep away insects and positioned or moved in ways that indicate the animal's physical or emotional state. [16]

Human tails

Tail-like structure on a female newborn from coccyx protrusion Gould Pyle 129.jpg
Tail-like structure on a female newborn from coccyx protrusion

In humans, tail bud refers to the part of the embryo which develops into the end of the spine. [17] However, this is not a tail. [18] Infrequently, a child is born with a "soft tail", which contains no vertebrae, but only blood vessels, muscles, and nerves, but this is regarded as an abnormality rather than a vestigial true tail, even when such an appendage is located where the tail would be expected. [19] [20] Fewer than 40 cases have been reported of infants with "true tails" containing the caudal vertebrae, a result of atavism. [21]

In 2024 scientists claimed to have found a genetic mutation that contributed to the loss of the tail in the common ancestor of humans and other apes. [22] [23]

Humans have a "tail bone" (the coccyx) attached to the pelvis; it comprises fused vertebrae, usually four, at the bottom of the vertebral column. It does not normally protrude externally - humans are an acaudal (or acaudate) species (i.e., tailless).

See also

Related Research Articles

<span class="mw-page-title-main">Anatomy</span> Study of the structure of organisms and their parts

Anatomy is the branch of biology concerned with the study of the structure of organisms and their parts. Anatomy is a branch of natural science that deals with the structural organization of living things. It is an old science, having its beginnings in prehistoric times. Anatomy is inherently tied to developmental biology, embryology, comparative anatomy, evolutionary biology, and phylogeny, as these are the processes by which anatomy is generated, both over immediate and long-term timescales. Anatomy and physiology, which study the structure and function of organisms and their parts respectively, make a natural pair of related disciplines, and are often studied together. Human anatomy is one of the essential basic sciences that are applied in medicine, and is often studied alongside physiology.

<span class="mw-page-title-main">Skeleton</span> Part of the body that forms the supporting structure

A skeleton is the structural frame that supports the body of most animals. There are several types of skeletons, including the exoskeleton, which is a rigid outer shell that holds up an organism's shape; the endoskeleton, a rigid internal frame to which the organs and soft tissues attach; and the hydroskeleton, a flexible internal structure supported by the hydrostatic pressure of body fluids.

<span class="mw-page-title-main">Scorpion</span> Predatory order of arachnids

Scorpions are predatory arachnids of the order Scorpiones. They have eight legs and are easily recognized by a pair of grasping pincers and a narrow, segmented tail, often carried in a characteristic forward curve over the back and always ending with a stinger. The evolutionary history of scorpions goes back 435 million years. They mainly live in deserts but have adapted to a wide range of environmental conditions, and can be found on all continents except Antarctica. There are over 2,500 described species, with 22 extant (living) families recognized to date. Their taxonomy is being revised to account for 21st-century genomic studies.

<span class="mw-page-title-main">Anatomical terms of location</span> Standard terms for unambiguous description of relative placement of body parts

Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position provides a definition of what is at the front ("anterior"), behind ("posterior") and so on. As part of defining and describing terms, the body is described through the use of anatomical planes and anatomical axes.

<span class="mw-page-title-main">Coccyx</span> Bone of the pelvis

The coccyx, commonly referred to as the tailbone, is the final segment of the vertebral column in all apes, and analogous structures in certain other mammals such as horses. In tailless primates since Nacholapithecus, the coccyx is the remnant of a vestigial tail. In animals with bony tails, it is known as tailhead or dock, in bird anatomy as tailfan. It comprises three to five separate or fused coccygeal vertebrae below the sacrum, attached to the sacrum by a fibrocartilaginous joint, the sacrococcygeal symphysis, which permits limited movement between the sacrum and the coccyx.

<span class="mw-page-title-main">Sacrum</span> Triangular-shaped bone at the bottom of the spine

The sacrum, in human anatomy, is a large, triangular bone at the base of the spine that forms by the fusing of the sacral vertebrae (S1–S5) between ages 18 and 30.

<span class="mw-page-title-main">Fish anatomy</span> Study of the form or morphology of fishes

Fish anatomy is the study of the form or morphology of fish. It can be contrasted with fish physiology, which is the study of how the component parts of fish function together in the living fish. In practice, fish anatomy and fish physiology complement each other, the former dealing with the structure of a fish, its organs or component parts and how they are put together, such as might be observed on the dissecting table or under the microscope, and the latter dealing with how those components function together in living fish.

<span class="mw-page-title-main">Somite</span> Each of several blocks of mesoderm that flank the neural tube on either side in embryogenesis

The somites are a set of bilaterally paired blocks of paraxial mesoderm that form in the embryonic stage of somitogenesis, along the head-to-tail axis in segmented animals. In vertebrates, somites subdivide into the dermatomes, myotomes, sclerotomes and syndetomes that give rise to the vertebrae of the vertebral column, rib cage, part of the occipital bone, skeletal muscle, cartilage, tendons, and skin.

<span class="mw-page-title-main">Telson</span> Hindmost division of an arthropod body

The telson is the hindmost division of the body of an arthropod. Depending on the definition, the telson is either considered to be the final segment of the arthropod body, or an additional division that is not a true segment on account of not arising in the embryo from teloblast areas as other segments. It never carries any appendages, but a forked "tail" called the caudal furca may be present. The shape and composition of the telson differs between arthropod groups.

<span class="mw-page-title-main">Oviraptorosauria</span> Extinct clade of dinosaurs

Oviraptorosaurs are a group of feathered maniraptoran dinosaurs from the Cretaceous Period of what are now Asia and North America. They are distinct for their characteristically short, beaked, parrot-like skulls, with or without bony crests atop the head. They ranged in size from Caudipteryx, which was the size of a turkey, to the 8-meter-long, 1.4-ton Gigantoraptor. The group is close to the ancestry of birds. Some researchers such as Maryanska et al (2002) and Osmólska et al. (2004) have proposed that they may represent primitive flightless birds. The most complete oviraptorosaur specimens have been found in Asia. The North American oviraptorosaur record is sparse.

<span class="mw-page-title-main">Autotomy</span> Self-amputation

Autotomy or 'self-amputation', is the behaviour whereby an animal sheds or discards one or more of its own appendages, usually as a self-defense mechanism to elude a predator's grasp or to distract the predator and thereby allow escape. Some animals have the ability to regenerate the lost body part later. Autotomy has multiple evolutionary origins and is thought to have evolved at least nine times independently in animals. The term was coined in 1883 by Leon Fredericq.

<span class="mw-page-title-main">Pygostyle</span> Skeletal condition involving fusion of caudal vertebrae into a single ossification

Pygostyle describes a skeletal condition in which the final few caudal vertebrae are fused into a single ossification, supporting the tail feathers and musculature. In modern birds, the rectrices attach to these. The pygostyle is the main component of the uropygium, a structure colloquially known as the bishop's nose, parson's nose, pope's nose, or sultan's nose. This is the fleshy protuberance visible at the posterior end of a bird that has been dressed for cooking. It has a swollen appearance because it also contains the uropygial gland that produces preen oil.

<i>Citipati</i> Genus of oviraptorid dinosaur

Citipati is a genus of oviraptorid dinosaur that lived in Asia during the Late Cretaceous period, about 75 million to 71 million years ago. It is mainly known from the Ukhaa Tolgod locality at the Djadochta Formation, where the first remains were collected during the 1990s. The genus and type species Citipati osmolskae were named and described in 2001. A second species from the adjacent Zamyn Khondt locality may also exist. Citipati is one of the best-known oviraptorids thanks to a number of well-preserved specimens, including individuals found in brooding positions atop nests of eggs, though most of them were initially referred to the related Oviraptor. These nesting specimens have helped to solidify the link between non-avian dinosaurs and birds.

Bird anatomy, or the physiological structure of birds' bodies, shows many unique adaptations, mostly aiding flight. Birds have a light skeletal system and light but powerful musculature which, along with circulatory and respiratory systems capable of very high metabolic rates and oxygen supply, permit the bird to fly. The development of a beak has led to evolution of a specially adapted digestive system.

<span class="mw-page-title-main">Ornithurae</span> Clade of dinosaurs

Ornithurae is a natural group which includes the common ancestor of Ichthyornis, Hesperornis, and all modern birds as well as all other descendants of that common ancestor.

<span class="mw-page-title-main">Rump (animal)</span> Part of an animal that is behind the loins and below the tail

The rump or croup, in the external morphology of an animal, is the portion of the posterior dorsum – that is, posterior to the loins and anterior to the tail. Anatomically, the rump corresponds to the sacrum.

<i>Glyptodon</i> Genus of large, heavily armored mammals

Glyptodon is a genus of glyptodont, an extinct group of large, herbivorous armadillos, that lived from the Pliocene, around 3.2 million years ago, to the early Holocene, around 11,000 years ago, in Brazil, Uruguay, Paraguay, Bolivia, Peru, Argentina, and Colombia. It is one of, if not the, best known genus of glyptodont. Glyptodon has a long and storied past, being the first named extinct cingulate and the type genus of the subfamily Glyptodontinae. Fossils of Glyptodon have been recorded as early as 1814 from Pleistocene aged deposits from Uruguay, though many were incorrectly referred to the ground sloth Megatherium by early paleontologists.

<span class="mw-page-title-main">Vertebral column</span> Bony structure found in vertebrates

The vertebral column, also known as the backbone or spine, is the core part of the axial skeleton in vertebrate animals. The vertebral column is the defining characteristic of vertebrate endoskeleton in which the notochord found in all chordates has been replaced by a segmented series of mineralized irregular bones called vertebrae, separated by fibrocartilaginous intervertebral discs. The dorsal portion of the vertebral column houses the spinal canal, a cavity formed by alignment of the neural arches that encloses and protects the spinal cord.

<span class="mw-page-title-main">Vertebra</span> Bone in the vertebral column

Each vertebra is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spinal segment and the particular species.

<span class="mw-page-title-main">Rectococcygeal muscle</span>

The rectococcygeal muscles are two bands of smooth muscle tissue arising from the 2nd and 3rd coccygeal vertebrae, and passing downward and forward to blend with the rectal longitudinal smooth muscle fibers on the posterior wall of the anal canal.

References

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  17. "Tail Bud". Merriam Webster. Retrieved 4 June 2020.
  18. "Developmental Stages in Human Embryos: Stage 16". the Endowment for Human Development. Retrieved 4 June 2020. What Kunitomo (1918) designated the "longest tail" at stage 16 is nothing of the kind but is merely the caudal end of the embryo, which will develop into the coccygeal region.
  19. "Human tail–caudal appendage: tethered cord". Nature . February 1, 2008. Retrieved 2009-04-28.
  20. "The 'human tail' causing tethered cervical cord". Nature . November 14, 2006. Retrieved 2009-04-28.
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  22. Weisberger, Mindy (March 23, 2024). "Why don't humans have tails? Scientists find answers in an unlikely place". CNN . Archived from the original on March 23, 2024. Retrieved March 24, 2024.
  23. Callaway, Ewen (2024-02-28). "How humans lost their tails — and why the discovery took 2.5 years to publish". Nature. doi:10.1038/d41586-024-00610-x.