Categories: Skeleton phene (incl. short stature & teeth)

Mendelian trait/disorder: yes

Mode of inheritance: Autosomal recessive

Disease-related: yes

Key variant known: no

Species-specific name: Otter

Species-specific description: The main distinguishing feature of this type of dwarfism was the short and crooked limbs and loose articulation. When the animals walked, their crooked forelimbs looked like elbows, which led a Dr Shattuck, who dissected a specimen in Boston, to suggest the name Ancon, from the Greek word for elbow (Humphreys, 1813). Ancons proved to be quite popular with New England farmers, because they were unable to jump over the low stone fences. Despite this perceived advantage, the breed appears to have become extinct by the end of the nineteenth century. A similar mutation occurred in 1919 in a Cheviot flock in Norway (Wriedt, 1925). Descendants of this mutant were exported to the Storrs Agricultural Experiment Station at the University of Connecticut, where they were studied by Landauer and Chang (1949) and Landauer (1950). Yet another similar mutation occurred in a Merino flock at the Livestock and Forage Research Center at McGregor, Texas, in 1962 (Shelton, 1968). Unfortunately, both of these mutants also became extinct.

History: The first recorded case of this type of dwarfism was a ram lamb born on a farm in Massachusetts in 1791 (Humphreys, 1813). An entertaining history of the mutation (on which the following account is largely based) has been presented by Schwartz and Vogel (1994). The farmer, Seth Wight (or Wright or Wite) kept the ram and, by mating him to related ewes, produced several more dwarfs, eventually giving rise to a new breed of short-legged sheep. The results of the initial matings and the true-breeding nature of the breed suggested that this form of dwarfism was an autosomal recessive trait. Humphreys (1813) suggested the name Otter for the breed, because of the "real or imaginary resemblance to that animal . . . by some supposed to have been caused by an unnatural intercourse" (i.e., by a mating between an otter and a sheep!) Darwin (1859, p. 30; 1868, p. 100) was impressed with the way in which offspring of Ancons mated to non-dwarf breeds "perfectly resemble either parent" rather than "being intermediate in character". He cited this as evidence against blending inheritance. Gidney (2006) reported that "The excavation of a 16th century archaeological site in Leicester, UK, produced sheep bones exhibiting the characteristic deformation of the Ancon dwarf but predating the earliest historical record of this mutation by some 200 years."