Conjoined Animals and Birds
Approximately one in 50,000 human births result in birth of conjoined twins. Conjoined twins are also very rare in the animal world due to the detrimental effect the conditions normally has on health and mobility. This hub is focused on examples where each twin is well-formed rather than evidenced only by isolated limbs or other body parts.
There is evidence that a tendency for conjoining may be inherited, as it is found at higher levels in some strains of a species (such as rabbits). It is also linked to environmental contamination in species such as fish.
Conjoining appears to be particularly rare in birds. These conjoined barn swallows were discovered in 2008. They are a very rare example, not only because this deformity seems to occur infrequently but because the few conjoined birds that are hatched typically do not live long enough to be discovered and recorded.
A case of conjoined buffalo twins is described here.
The aquatic environment may be more supportive of conjoined body structure. This example of tilapia twins connected at the stomach is kept in a Bangkok aquarium. A similar conformation has also been seen in arowana (2006).
This taxidermy example exists of a conjoined fawn, but as with any preserved specimen it is difficult to judge whether it is authentic.
A fetal example (2010).
In 2001 this pair of conjoined crocodiles was hatched in the Samut Prakarn Crocodile Farm. This conformation with attachment at the pelvis seems to be more common with reptiles, such as these turtles.
There are quite a few two headed snakes such as this python. The can be raised to adulthood with careful feeding. And it is more common to see lateral (side-by-side) conjoining even in turtles (see below).
Other examples of conjoining have been documented in geckos.
Several cases of conjoined kittens are collected online; I have yet to find any adult examples. (Fetal examples via: Prof Mundie)
The Buckhorn Saloon has a taxidermy example of conjoined calves on display.
Conjoining may even happen in insects such as ants.
Whole animals such as mice have been surgically joined together so that they share a common blood supply. This procedure is referred to as parabiosis.
There are also gaff conjoined animals that are produced after death by taxidermy.
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- Chai, C. K., & Crary, D. D. (1971). Conjoined twinning in rabbits. Teratology, 4(4), 433-444.
- Harris SB, Goldenthal EI (1977). Conjoined Twins (Cephalothoracopagus) in a Charles River CD Rat. Veterinary Pathology, 14, 519. [pdf]
- Ingalls, T. H., Philbrook, F. R., & Majima, A. (1969). Conjoined twins in zebra fish. Archives of Environmental Health: An International Journal, 19(3), 344-352.
- O'Neill JA, Holcomb GW. (1988). Surgical experience with thirteen conjoined twins. Annals of surgery, 208, 299 -312.