Manx cat
In 2013, prior to initiation of the Manx Cat Genome Project (below), genetic mutations in the brachyury gene were shown to be responsible for failure of tail development in the Manx cat, as well as four other tailess breeds of cat. Mutations in orthologs of this gene have been shown to cause tail-loss defects in a number of other species, notably mouse. Mutations in the human version of the brachyury gene are associated with a range of neural tube defects.