The first cat that lay the foundation for this breed was a shorthaired, curly coated dilute calico female found in a litter of normal domestic cats born in 1987. A dominant mutation in the gene causes the coat to become curly. It is presumed that this was a spontaneous mutation that was then passed on to her offspring.
The standard calls for a medium to large cat, with heavy boning. The head type is similar to the British Shorthair, but with more roundness to the head. The body is muscular and rectangular, with a slight rise to the hind quarters.
Selkirks come in both "shorthaired" and longhaired varieties. The original cat carried the longhair gene. The coat is thick and plush and falls in loose curls. The coat is soft in texture. Selkirks come in a rainbow of colours, including the "pointed" colours. Both British Shorthairs and Longhairs and Persian cats are an allowed outcross. Kittens appear very curly at birth, but then they go through an awkward "straight" stage. Upon full maturity, the coat comes into its full glory.
Selkirks do come with "normal" hair, these are called Straights.