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The cephalic index of a vertebrate is the ratio between the width (side to side) and length (front to back) of its cranium (skull). This ratio does not concern the muzzle or face, and thus is distinct from the ''craniofacial ratio'', which compares the size of the cranium to the length of the muzzle. The two measures are often confused in descriptions of dog breeds. The cephalic index is used to classify animals into three groups: Image:Chihuahua 01 K.jpg Image:LakiJustbluein.jpg Brachycephalic (literally 'short-headed'): the length of the cranium is shorter than the width, giving the top and sides of the cranium a round shape, often referred to as 'apple-head'. File:CPRileySnow.jpg File:American Shorthair.jpg Mesaticephalic or mesocephalic ('middle-headed'): the length and width are equal, giving a square shape. When dealing with animals, especially dogs, the more appropriate and commonly used term is not "mesocephalic", but rather "mesaticephalic", which is a ratio of head to nasal cavity.〔Evans, Howard (date unknown). Miller's Anatomy of the Dog, 3rd edition, page 132〕〔Retrieved from http://medical-dictionary.thefreedictionary.com/mesaticephalic.〕 Image:Kufa charta - borzoja.jpg Image:Savannah Cat closeup.jpg Dolichocephalic ('long-headed): the length is greater than the width. Breeds of each group are listed in Cephalic index#Use in animal breeding (Modern). == See also == * Artificial selection 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Cephalic index in cats and dogs」の詳細全文を読む スポンサード リンク
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