Cephalic index in cats and dogs

Cephalic index is the charting of or classification of the Cephalic ratio; the cranial width as compared to cranial length. The cephalic index refers to the cranium and its relative size, comparing cranial length to cranial width.

This ratio does not include the muzzle or face and its relative size as compared to the cranium. The structure and size of the muzzle or face as related to the cranium or skull is classified as the craniofacial ratio, (cranio- combining form meaning head or skull and facial- combining form referring to the facial structures).

Many dog breeds are often erroneously categorized within the cephalic index based on their craniofacial ratio, (the size and structure of the face or muzzle as compared to the size and structure of the cranium), rather than their cephalic ratio, (the cranial width as compared to cranial length).

Cephalic Index

The cephalic index has three classifications:

Brachycephalic

Meaning short headed or broad headed, wherein the length of the cranium is shorter than the width. This gives the top and sides of the cranium a round shape, often referred to as 'apple-head'.

Wide or oval cranium.

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  Brachycephalic dog

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  Brachycephalic cat

Mesocephalic

Meaning the ratio of cranial length is equal to cranial width, normal or medium proportion.

Square cranium.

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  Mesocephalic dog

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  Mesocephalic cat

Dolichocephalic

Meaning long headed, wherein the cranial length is greater than the cranial width.

Long, rectangular cranium.

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  Dolichocephalic dog

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  Dolichocephalic cat

References

• Sparks, Corey S. and Jantz Richard L.; (November 2002). A Reassessment of Human Cranial Plasticity: Boas revisited.
• Miriam Websters New Collegiate Dictionary