Giraffidae
The Giraffidae are a family of ruminant artiodactyl mammals that share a common ancestor with cervids and bovids. This family, once a diverse group spread throughout Eurasia and Africa, presently comprises only two extant genera, the giraffe and the okapi. Both are confined to sub-Saharan Africa: the giraffe to the open savannas, and the okapi to the dense rainforest of the Congo. The two genera look very different on first sight, but share a number of common features, including a long, dark-coloured tongue, lobed canine teeth, and horns covered in skin, called ossicones.
Taxonomy
Evolutionary background
The giraffids are ruminants of the clade Pecora. Other extant pecorans are the families Antilocapridae, Cervidae, Moschidae, and Bovidae. The exact interrelationships among the pecorans have been debated, mainly focusing on the placement of Giraffidae, but a recent large-scale ruminant genome sequencing study suggests Antilocapridae are the sister taxon to Giraffidae. The ancestors of pronghorn diverged from the giraffids in the Early Miocene. This was in part of a relatively late mammal diversification following a climate change that transformed subtropical woodlands into open savannah grasslands.The fossil record of giraffids and their stem-relatives is quite intensive, with fossil of these taxa include Gelocidae, Palaeomerycidae, Prolibytheridae, and Climacoceratidae. It is thought the palaeomerycids is the ancestral group that given rise to the prolibytherids, climacoceratids and the giraffids, all three forming a clade of pecorans known as Giraffomorpha. The relationship between the climacoceratids and giraffids is supported by the presence of a bilobed canine, and have been postulated into two hypotheses. One is the climacoceratids were the ancestors of the sivatheres, as both groups were large, deer-like giraffoids with brancing antler-like ossicones, while an extinct basal group of giraffoids, canthumerycines, evolved into the ancestors of Giraffidae. Another more commonly supported hypothesis is climacoceratids were merely the sister clade to giraffids, with sivatheres being either basal giraffids or descended from a lineage that also includes the okapi. While the current range of giraffids today is in Africa, the fossil record of the group has shown this family was once widespread throughout of Eurasia.
Below is the phylogenetic relationships of giraffomorphs after Solounias, Sánchez et al. and Ríos et al. :
Classification
Below is the total taxonomy of valid extant and fossil taxa.Family Giraffidae J.E.Gray, 1821
- Basal extinct giraffids
- * †Csakvarotherium Kretzoi, 1930
- ** †Csakvarotherium hungaricum Kretzoi, 1930
- * †Palaeogiraffa Bonis & Bouvrain, 2003
- ** †Palaeogiraffa macedoniae
- ** †Palaeogiraffa major Bonis & Bouvrain, 2003
- ** †Palaeogiraffa pamiri
- * †Propalaeomeryx Lydekker, 1883
- ** †Propalaeomeryx sivalensis Lydekker, 1883
- * †Umbrotherium Abbazzi, Delfino, Gallai, Trebini & Rook, 2008
- ** †Umbrotherium azzarolii Abbazzi, Delfino, Gallai, Trebini & Rook, 2008
- * †Vishnutherium Lydekker, 1876
- ** †Vishnutherium iravadicum Lydekker 1876
- Subfamily †Bohlininae Solounias, 2007
- * †Bohlinia Matthew, 1929
- ** †Bohlinia adoumi Likius, Vignaud & Brunet, 2007
- ** †Bohlinia attica
- ** †Bohlinia nikitiae Kostopoulos, Koliadimou & Koufos, 1996
- * †Honanotherium Bohlin, 1926
- ** †Honanotherium bernori Solounias & Danowitz, 2016
- ** †Honanotherium schlosseri
- Subfamily †Canthumerycinae Hamilton, 1978
- * †Georgiomeryx Paraskevaidis, 1940
- ** †Georgiomeryx georgalasi Paraskevaidis, 1940
- * †Canthumeryx Hamilton 1973
- ** †Canthumeryx sirtensis Hamilton 1973
- Subfamily Giraffinae J.E.Gray, 1821
- * Giraffa Brisson, 1762
- ** Giraffa camelopardalis super-complex
- *** Giraffa giraffa complex
- **** Giraffa angolensis Lydekker, 1903 – Angolan giraffe
- **** Giraffa giraffa – South African giraffe
- *** Giraffa tippelskirchii complex Matschie, 1898
- **** Giraffa thornicrofti Lydekker, 1911 – Rhodesian giraffe
- **** Giraffa tippelskirchii Matschie, 1898 – Masai giraffe
- *** Giraffa reticulata de Winton, 1899 – Reticulated giraffe
- *** Giraffa camelopardalis complex
- **** Giraffa peralta Thomas, 1898 – West African giraffe
- **** Giraffa antiquorum Jardine & Swainson, 1835 – Kordofan giraffe
- **** Giraffa camelopardalis – Northern giraffe
- ***** Giraffa camelopardalis rothschildi Lydekker, 1903 – Rothschild's giraffe
- ***** Giraffa camelopardalis camelopardalis – Nubian giraffe
- ** †Giraffa jumae Leakey, 1967
- ** †Giraffa priscilla Pilgrim, 1911
- ** †Giraffa punjabiensis Pilgrim, 1911
- ** †Giraffa pygmaea Harris, 1976
- ** †Giraffa sivalensis
- ** †Giraffa stillei
- Subfamily †Giraffokerycinae Solounias, 2007
- * †Giraffokeryx Pilgrim, 1910
- ** †Giraffokeryx anatoliensis Geraads & Aslan, 2003
- ** †Giraffokeryx primaevus
- ** †Palaeotragus coelophrys
- ** †Palaeotragus germaini Arambourg, 1959
- ** †Palaeotragus inexspectatus
- ** †Palaeotragus lavocanti Heintz, 1976
- ** †Palaeotragus robinsoni Crusafont-Pairó, 1979
- ** †Palaeotragus rouenii Gaudry, 1861
- ** †Palaeotragus tungurensis Colbert, 1936
- Subfamily †Samotheriinae Hamilton, 1978
- * †Decennatherium Crusafont Pairó, 1952
- ** †Decennatherium rex Ríos, Sánchez & Morales, 2017
- ** †Decennatherium pachecoi Crusafont Pairó, 1952
- * †Samotherium Forsyth Major, 1888
- ** †Samotherium major Bohlin, 1926
- ** †Samotherium neumayri
- ** †Samotherium sinense
- * †Shansitherium Killgus, 1922
- ** †Shansitherium tafeli Killgus, 1922
- †Subfamily Sivatheriinae Bonaparte, 1850
- * †Birgerbohlinia Crusafont Pairó, 1952
- ** †Birgerbohlinia schaubi Crusafont Pairó, 1952
- * †Bramatherium Falconer, 1845
- ** †Bramatherium giganteus Khan & Sarwar, 2002
- ** †Bramatherium grande
- ** †Bramatherium magnum
- ** †Bramatherium megacephalum
- ** †Bramatherium perimense Falconer, 1845
- ** †Bramatherium progressus Khan, Sarwar & Khan, 1993
- ** †Bramatherium suchovi Godina, 1977
- * †Helladotherium Gaudry, 1860
- ** †Helladotherium duvernoyi
- * †Sivatherium Falconer & Cautley, 1836
- ** †Sivatherium giganteum Falconer & Cautley, 1836
- ** †Sivatherium hendeyi Harris, 1976
- ** †Sivatherium maurusium
Characteristics
Giraffids share many common features with other ruminants. They have cloven hooves and cannon bones, much like bovids, and a complex, four-chambered stomach. They have no upper incisors or upper canines, replacing them with a tough, horny pad. An especially long diastema is seen between the front and cheek teeth. The latter are selenodont, adapted for grinding up tough plant matter. Like most other ruminants, the dental formula for giraffids is. Giraffids have prehensile tongues.
The extant giraffids, the forest-dwelling okapi and the savannah-living giraffe, have several features in common, including a pair of skin-covered horns, called ossicones, up to long ; a long, black, prehensile tongue; lobed canine teeth; patterned coats acting as camouflage; and a back sloping towards the rear. The okapi's neck is long compared to most ruminants, but not nearly so long as the giraffe's. Male giraffes are the tallest of all mammals, their horns reach above the ground and their shoulder, whereas the okapi has a shoulder height of.
Distribution
The two extant genera are now confined to sub-Saharan Africa. The okapi is restricted to a small range in the northern rainforest of the Democratic Republic of Congo. Although the range of the giraffe is considerably larger, it once covered an area twice the present size — all parts of Africa that could offer an arid and dry landscape furnished with trees.Behavior
The social structure and behavior is markedly different in okapis and giraffes, but although little is known of the okapi's behavior in the wild, a few things are known to be present in both species:- They have an ambling gait similar to camels, with their weight supported alternately by their left and right legs, while their necks maintain balance. Giraffes can run up to this way and are documented to have covered in the Sahel during the dry season.
- The dominance hierarchy, which has been well-documented among giraffes, has also been seen among captive okapis. An adult giraffe head can weigh, and if necessary, male giraffes establish a hierarchy among themselves by swinging their heads at each other, horns first, a behavior known as "necking". A subordinate okapi signals submission by placing its head and neck on the ground.
- Giraffes and okapis are normally silent, but both have a range of vocalizations, including coughing, snorting, moaning, hissing, and whistling. Giraffes have been suggested to be able to communicate using infrasonic sounds like elephants and blue whales.