of skins, mares were significantly longer and slightly taller than stallions, whereas the stallions of extant zebras are the largest. Its coat pattern was unique among equids: zebra-like in the front but more like a horse in the rear. It had brown and white stripes on the head and neck, brown upper parts and a white belly, tail and legs. The stripes were boldest on the head and neck and became gradually fainter further down the body, blending with the reddish brown of the back and flanks, until disappearing along the back. It appears to have had a high degree of polymorphism, with some having almost no stripes and others having patterns similar to the extinct southern population of Burchell's zebra, where the stripes covered most of the body except for the hind parts, legs and belly. It also had a broad dark dorsal stripe on its back. It had a standing mane with brown and white stripes. The only quagga to have been photographed alive was a mare at the Zoological Society of London's Zoo. Five photographs of this specimen are known, taken between 1863 and 1870. On the basis of photographs and written descriptions, many observers suggest that the stripes on the quagga were light on a dark background, unlike other zebras. The German naturalist Reinhold Rau, pioneer of the Quagga Project, claimed that this is an optical illusion: that the base colour is a creamy white and that the stripes are thick and dark. Living in the very southern end of the plains zebra's range, the quagga had a thick winter coat that moulted each year. Its skull was described as having a straight profile and a concave diastema, and as being relatively broad with a narrow occiput. Like other plains zebras, the quagga did not have a dewlap on its neck as the mountain zebra does. The 2004 morphological study found that the skeletal features of the southern Burchell's zebra population and the quagga overlapped, and that they were impossible to distinguish. Some specimens also appeared to be intermediate between the two in striping, and the extant Burchell's zebra population still exhibits limited striping. It can therefore be concluded that the two subspecies graded morphologically into each other. Today, some stuffed specimens of quaggas and southern Burchell's zebra are so similar that they are impossible to definitely identify as either, since no location data was recorded.