Giraffidae

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Giraffidae
Temporal range: 20–0  Ma
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S
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Early Miocene - recent
Okapi.bristol.600pix.jpg
An okapi in Bristol Zoo, England
Giraffe Mikumi National Park.jpg
Masai giraffe (G. tippelskirchi) at the Mikumi National Park, Tanzania
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Artiodactyla
Superfamily: Giraffoidea
Family: Giraffidae
Gray, 1821
Subfamilies

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 (one or more species of Giraffa , depending on taxonomic interpretation) and the okapi (the only known species of 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 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.

Contents

Taxonomy

ImageGenusLiving species
Okapia johnstoni1.jpg Okapia
Australia Zoo Giraffe-2 (17998331829).jpg Giraffa

Evolutionary background

Shansitherium and Palaeotragus microdon, two giraffids from the Miocene of Asia Shansitherium fuguensis.JPG
Shansitherium and Palaeotragus microdon, two giraffids from the Miocene of Asia

The giraffids are ruminants of the clade Pecora. Other extant pecorans are the families Antilocapridae (pronghorns), Cervidae (deer), Moschidae (musk deer), and Bovidae (cattle, goats and sheep, wildebeests and allies, and antelopes). 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, as shown in the cladogram below. [1]

Ruminantia
Tragulina

Tragulidae Tragulus napu - 1818-1842 - Print - Iconographia Zoologica - Special Collections University of Amsterdam - (white background).jpg

Pecora

Antilocapridae Antilocapra white background.jpg

Giraffidae Giraffa camelopardalis Brockhaus white background.jpg

Cervidae The deer of all lands (1898) Hangul white background.png

Bovidae Birds and nature (1901) (14562088237) white background.jpg

Moschidae Moschus chrysogaster white background.jpg

The ancestors of pronghorn diverged from the giraffids in the Early Miocene. [1] 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. [2] [3] 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. [2] [4] The relationship between the climacoceratids and giraffids is supported by the presence of a bilobed canine, [2] 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 branching antler-like ossicones, while an extinct basal group of giraffoids, canthumerycines, evolved into the ancestors of Giraffidae. [3] Another more commonly supported hypothesis is climacoceratids were merely the sister clade to giraffids, with sivatheres being either basal giraffids [2] or descended from a lineage that also includes the okapi. [5] 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. [2] [3] [5]

Below is the phylogenetic relationships of giraffomorphs after Solounias (2007), [2] Sánchez et al. (2015) [4] and Ríos et al. (2017): [5]

Giraffomorpha

Palaeomerycidae

Giraffoidea

Prolibytheridae

Climacoceratidae

Giraffidae

Canthumerycinae [lower-alpha 1]

Giraffokerycinae

Bohlininae

Giraffinae

Palaeotraginae

Okapiinae

Samotheriinae [lower-alpha 2]

Sivatheriinae

Classification

Skeletal illustration of Helladotherium, now extinct Helladotherium.jpg
Skeletal illustration of Helladotherium , now extinct
Skeletal mount of Palaeotragus on display at the Tianjin Natural History Museum. Palaeotragus-Tianjin Natural History Museum.jpg
Skeletal mount of Palaeotragus on display at the Tianjin Natural History Museum.
Skeletal mount of Shansitherium tafeli on display at the Beijing Museum of Natural History. Shansitherium-Beijing Museum of Natural History.jpg
Skeletal mount of Shansitherium tafeli on display at the Beijing Museum of Natural History.

Below is the total taxonomy of valid extant and fossil taxa (as well as junior synonyms which are listed in the brackets).

Family GiraffidaeJ.E.Gray, 1821

Characteristics

Two giraffes Giraffes Mikumi National Park.jpg
Two giraffes

The giraffe stands 5–6 m (16–20 ft) tall, with males taller than females. The giraffe and the okapi have characteristic long necks and long legs. Ossicones are present on males and females in the giraffe, but only on males in the okapi. [6]

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. [7] Like most other ruminants, the dental formula for giraffids is 0.0.3.33.1.3.3. Giraffids have prehensile tongues (specially adapted for grasping). [8]

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 15 cm (5.9 in) long (absent in female okapis); 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 5.5 m (18 ft) above the ground and their shoulder 3.3 m (11 ft), whereas the okapi has a shoulder height of 1.7 m (5 ft 7 in). [9]

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. [9]

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: [9]

Giraffes are sociable, where as okapis live mainly solitary lives. Giraffes temporarily form herds of up to 20 individuals; these herds can be mixed or uniform groups of males and females, young and adults. Okapis are normally seen in mother-offspring pairs, although they occasionally gather around a prime food source. Giraffe are not territorial, but have ranges that can dramatically vary between 5 and 654 km2 (1.9 and 252.5 sq mi) — depending on food availability, whereas okapis have individual ranges about 2.5–5 km2 (0.97–1.93 sq mi) in size.

Notes

  1. A grade of giraffids.
  2. A paraphyletic grade of palaeotragines ancestral to Sivatheriinae.

Related Research Articles

Giraffe Tall African ungulate

The giraffe (Giraffa) is an African artiodactyl mammal, the tallest living terrestrial animal and the largest ruminant. It is traditionally considered to be one species, Giraffa camelopardalis, with nine subspecies. However, the existence of up to nine extant giraffe species has been described, based upon research into the mitochondrial and nuclear DNA, as well as morphological measurements of Giraffa. Seven other prehistoric species, known from fossils, are extinct.

Okapi Species of mammal

The okapi, also known as the forest giraffe, Congolese giraffe, or zebra giraffe, is an artiodactyl mammal that is endemic to the northeast Democratic Republic of the Congo in central Africa. Although the okapi has striped markings reminiscent of zebras, it is most closely related to the giraffe. The okapi and the giraffe are the only living members of the family Giraffidae.

Ungulate Group of animals that use the tips of their toes or hooves to walk on

Ungulates are members of the diverse clade Ungulata which primarily consists of large mammals with hooves. These include odd-toed ungulates such as horses, rhinoceroses, and tapirs; and even-toed ungulates such as cattle, pigs, giraffes, camels, sheep, deer, and hippopotamuses. Cetaceans such as whales, dolphins, and porpoises are also classified as even-toed ungulates, although they do not have hooves. Most terrestrial ungulates use the hoofed tips of their toes to support their body weight while standing or moving.

Even-toed ungulate Order of mammals

The even-toed ungulates are ungulates—hoofed animals—which bear weight equally on two of their five toes: the third and fourth. The other three toes are either present, absent, vestigial, or pointing posteriorly. By contrast, odd-toed ungulates bear weight on an odd number of the five toes. Another difference between the two with the exception of Suina many other even-toed ungulates digest plant cellulose in one or more stomach chambers rather than in their intestine as the odd-toed ungulates do.

Pecora Infraorder of mammals

Pecora is an infraorder of even-toed hoofed mammals with ruminant digestion. Most members of Pecora have cranial appendages projecting from their frontal bones; only two extant genera lack them, Hydropotes and Moschus. The name “Pecora” comes from the Latin word pecus, which means “horned livestock”. Although most pecorans have cranial appendages, only some of these are properly called “horns”, and many scientists agree that these appendages did not arise from a common ancestor, but instead evolved independently on at least two occasions. Likewise, while Pecora as a group is supported by both molecular and morphological studies, morphological support for interrelationships between pecoran families is disputed.

<i>Sivatherium</i> Extinct genus of mammals

Sivatherium is an extinct genus of giraffids that ranged throughout Africa to the Indian subcontinent. The species Sivatherium giganteum is, by weight, one of the largest giraffid known, and also one of the largest ruminants of all time. The Afro-Asiatic species, S. maurusium, was once placed within the genus "Libytherium".

Ossicone

Ossicones are columnar or conical skin-covered bone structures on the heads of giraffes, male okapi, and some of their extinct relatives. Ossicones are distinguished from the superficially similar structures of horns and antlers by their unique development and a permanent covering of skin and fur.

Giraffokeryx is an extinct genus of medium-sized giraffids known from the Miocene of the Indian subcontinent and Eurasia. It is distinguished from other giraffids by the four ossicones on its head; one pair in front of the eyes on the anterior aspect of the frontal bone and the other behind the eyes in the frontoparietal region overhanging the temporal fossae. It has a brachydont dentition like in other giraffids and its legs and feet are of medium length. Giraffokeryx is considered monotypic by most authors, in the form of G. punjabiensis, but other species have been assigned to the genus:

<i>Honanotherium</i> Extinct genus of mammals

Honanotherium is a genus of extinct giraffid from the late Miocene of Henan Province, China, and East Azerbaijan Province, northwestern Iran. It was closely related to Bohlinia and was once thought to be ancestral to the modern giraffe. The living animal would have resembled a modern giraffe, but was somewhat shorter, with more massive ossicones.

<i>Bramatherium</i> Extinct genus of mammals

Bramatherium is an extinct genus of giraffids that ranged from India to Turkey in Asia. It is closely related to the larger Sivatherium.

Palaeomerycidae Extinct family of deer

The Palaeomerycidae are an extinct family of ruminants in the order Artiodactyla, probably ancestral to deer and musk deer. Palaeomerycids lived in North America, Europe, Africa and Asia from 33 to 4.9 million years ago, existing for about 28 million years; one species was also reported from South America, but its identity as a palaeomerycid was subsequently disputed.

<i>Helladotherium</i> Extinct genus of mammals

Helladotherium is an extinct genus of Sivatherine Giraffid from Europe, Africa, and Asia during the Miocene. The most complete skeleton is that of a female, based on a comparison with an intact female Sivatherium giganteum skull.

Hydaspitherium is an extinct genus of giraffid artiodactyls.

Giraffoidea Superfamily of mammals

Giraffoidea is a superfamily that includes the families Climacoceratidae, Antilocapridae, and Giraffidae. The only extant members in the superfamily are the pronghorn, giraffe, and okapi. The Climacoceratidae are also placed in the superfamily, but were originally placed within the family Palaeomerycidae.

This is a list of the taxonomic contributions of Major Percy Horace Gordon Powell-Cotton.

This article records new taxa of fossil mammals that were described during the year 2018, as well as other significant discoveries and events related to the paleontology of mammals in the year 2018.

References

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