Primitive markings are also called countershading, false dun, or its scientific name non-dun1. Primitive markings are dorsal stripes, leg barring, shoulder stripes, and cobwebbing/spiderwebbing. There is a genetic test for primitive markings. Primitive markings, particularly dorsal stripes, are common in Chincoteague Ponies.
Dun (D) is the original color of horses and they have primitive markings and are diluted. Dun is dominant and can not skip generations. Dun is not found in Chincoteague Ponies.
Non-dun1 (nd1) ponies have primitive markings but are not diluted. A pony with one or two copies of Nd1 can have primitive markings. nd1 is found in Chincoteague Ponies.
Non-dun2 (nd2) causes ponies to not have primitive markings and are not diluted. A pony with two copies of nd2 will not have primitive markings. nd2 is found in Chincoteague Ponies.
Foals often have primitive markings that is later lost after the foal coat is shed. This is presumed to be a form of camouflage.