Giraffidae introduction

Family Giraffidae

The Giraffidae has two extant genera: the giraffe (one species: Giraffa) and the okapi (one species: Okapia). Both are confined to sub-Saharan Africa: the giraffe to the open savannas, and the okapi to the dense rainforest of the Congo. The giraffe is the tallest living mammal, which attains a height of up to 5.8 m but possess the same number of cervical vertebrae - seven - as most other mammals.

This family are browsers and low-crowned teeth. Both the giraffe and okapi possess a long, prehensile tongue with which they browse. Leaves form the principal diet of both species.

A pair of skin-covered bony knobs (known as ossicones) are present in both species: in Okapia they grow from the frontal bones in males only; in Giraffa both sexes have ossicones on the parietal bones. Ossicones of modern giraffes are short and unbranched, and are never shed. In Giraffa, layers of bone are often laid along the suture between the frontal and nasal bones, forming a third protuberance which is especially prominent in adult males. At birth, the ossicones are present as cartilaginous knobs, which ossify, grow, and fuse with the skull with age.

Using fossil calibrations, we estimated the emergence of Giraffidae at ~23 Mya. And our results support a sister-group relationship for Antilocapridae and Giraffidae, representing the oldest branch among the extant pecoran families.


  1. Hackmann T J, Spain J N. Invited review: ruminant ecology and evolution: perspectives useful to ruminant livestock research and production.[J]. Journal of Dairy Science, 2010, 93(4):1320-1334.
  2. Hernández F M, Vrba E S. A complete estimate of the phylogenetic relationships in Ruminantia: a dated species-level supertree of the extant ruminants[M]. 2005.
  3. Hofmann R R. Evolutionary steps of ecophysiological adaptation and diversification of ruminants: a comparative view of their digestive system[J]. Oecologia, 1989, 78(4):443-457.
  4. Davis E B, Brakora K A, Lee A H. Evolution of ruminant headgear: a review[J]. Proceedings Biological Sciences, 2011, 278(1720):2857-2865.

The Giraffidae Family Tree