Figure 1 - Phenotypes of Rhodesian and Thai Ridgeback dogs.

From the following article

Duplication of FGF3, FGF4, FGF19 and ORAOV1 causes hair ridge and predisposition to dermoid sinus in Ridgeback dogs

Nicolette H C Salmon Hillbertz, Magnus Isaksson, Elinor K Karlsson, Eva Hellmén, Gerli Rosengren Pielberg, Peter Savolainen, Claire M Wade, Henrik von Euler, Ulla Gustafson, Åke Hedhammar, Mats Nilsson, Kerstin Lindblad-Toh, Leif Andersson & Göran Andersson

Nature Genetics 39, 1318 - 1320 (2007) Published online: 30 September 2007


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(a,b) The dorsal hair ridge of Rhodesian Ridgeback (a) and Thai Ridgeback dogs (b). (c) A ridgeless Rhodesian Ridgeback dog. (d) Light micrograph of ridge skin taken from the dorsal median plane with cross-sectioned, laterally oriented hair follicles (arrow) and sebaceous glands in the dermis (objective lens times 4). (e) Corresponding cross-section from a ridgeless dog. Note that the hair follicles are caudally oriented in the median plane (arrow) (objective lens times 4). (f) The full extension of a dermoid sinus, extending from the upper dermis to the nuchal ligament, which overlays the cervical spinous process. The dermoid sinus–affected Rhodesian Ridgeback was 6 weeks old at the time of euthanasia. (g) Light micrograph of a cross-sectioned dermoid sinus with hair and keratin debris in the lumen covered by a stratified squamous keratinized epithelium. In the upper portion, appendages such as a hair follicle (filled arrow) and sebaceous glands (*) are seen; in the right corner, a hair follicle with multiple hair shafts is indicated (open arrow); (objective lens times 20). At lower magnification, the whole dermoid sinus is seen with the surrounding loose connective tissue (inset, objective lens times 10).