| Hyaenidae | |
|---|---|
 A Spotted Hyena | |
| Scientific Classification | |
| Kingdom | Animalia |
| Phylum | Chordata |
| Class | Mammalia |
| Order | Carnivora |
| Family | Hyaenidae |
Hyaenidae is a family from the Carnivora order. It's including 4 extant species.
Characteristics
Hyenas have relatively short torsos and are fairly massive and wolf-like in build, but have lower hind quarters, high withers and their backs slope noticeably downward toward their croups. The forelegs are high, while the hind legs are very short and their necks are thick and short. Their skulls superficially resemble those of large canids, but are much larger and heavier, with shorter facial portions. Hyenas are digitigrade, with the fore and hind paws having four digits each and sporting bulging pawpads. Like canids, hyenas have short, blunt, non-retractable claws. Their pelage is sparse and coarse with poorly developed or absent underfur. Most species have a rich mane of long hair running from the withers or from the head. With the exception of the spotted hyena, hyaenids have striped coats, which they likely inherited from their viverrid ancestors. Their ears are large and have simple basal ridges and no marginal bursa. Their vertebral column, including the cervical region are of limited mobility. Hyenas have no baculum. Hyenas have an additional pair of ribs than canids, and their tongues are rough like those of felids and viverrids. Males in most hyena species are larger than females, though the spotted hyena is exceptional, as it is the female of the species that outweighs and dominates the male. Also, unlike other hyenas, the female spotted hyena's external genitalia closely resembles that of the male. Their dentition is similar to that of the Felidae, but is more specialised for consuming coarse food and crushing bones. The carnassials, especially the upper, are very powerful and are shifted far back to the point of exertion of peak pressure on the jaws. The other teeth, save for the underdeveloped upper molars, are powerful, with broad bases and cutting edges. The canines are short, but thick and robust. Labiolingually, their mandibles are much stronger at the canine teeth than in canids, reflecting the fact that hyenas crack bones with both their anterior dentition and premolars, unlike canids, which do so with their post-carnassial molars. The strength of their jaws is such that both striped and spotted hyenas have been recorded to kill dogs with a single bite to the neck without breaking the skin. The spotted hyena is renowned for its strong bite proportional to its size, but a number of other animals (including the Tasmanian devil) are proportionately stronger. The aardwolf has greatly reduced cheek teeth, sometimes absent in the adult, but otherwise has the same dentition as the other three species.
Evolution
Hyenas originated in the jungles of Miocene Eurasia 22 million years ago, when most early feliform species were still largely arboreal. The first ancestral hyenas were likely similar to the modern banded palm civet; one of the earliest hyena species exhumed, Plioviverrops, was a lithe, civet-like animal that inhabited Eurasia 20–22 million years ago, and is identifiable as a hyaenid by the structure of the middle ear and dentition. The lineage of Plioviverrops prospered, and gave rise to descendants with longer legs and more pointed jaws, a direction similar to that taken by canids in North America.The descendants of Plioviverrops reached their peak 15 million years ago, with more than 30 species having been identified. Unlike most modern hyena species, which are specialised bone-crushers, these dog-like hyenas were nimble-bodied, wolfish animals; one species among them was Ictitherium viverrinum, which was similar to a jackal. The dog-like hyenas were very numerous; in some Miocene fossil sites, the remains of Ictitherium and other dog-like hyenas outnumber those of all other carnivores combined. The decline of the dog-like hyenas began 5–7 million years ago during a period of climate change, which was exacerbated when canids crossed the Bering land bridge to Eurasia. One species, Chasmaporthetes ossifragus, managed to cross the land bridge into North America, being the only hyena to do so. Chasmopothertes managed to survive for some time in North America by deviating from the cursorial and bone-crushing niches monopolised by canids, and developing into a cheetah-like sprinter. Most of the dog-like hyenas had died off by 1.5 million years ago.By 10–12 million years ago, the hyena family had split into two distinct groups; that of the dog-like hyenas and the bone-crushing hyenas. The arrival of the ancestral bone-crushing hyenas coincided with the decline of the similarly built but unrelated Percrocutidae family. The bone-crushing hyenas survived the devastating changes in climate and the arrival of canids, which wiped out the dog-like hyenas, though they never crossed into North America, as their niche there had already been taken by the Borophaginae family. By 5 million years ago, the bone-crushing hyenas became the dominant scavengers of Eurasia, primarily feeding on large herbivore carcasses felled by sabre-toothed cats. One genus, Pachycrocuta, was a 200 kg (440 lb) mega-scavenger that could splinter the bones of elephants. With the decline of large herbivores by the late ice age, Pachycrocuta was replaced by the smaller Crocuta.
Genera
Family Hyaenidae
†Tongxinictis †Subfamily Ictitheriinae †Herpestides H. aegypticus H. aequatorialis H. antiquus H. compactus †Plioviverrops †Ictitherium I. viverrinum I. syvalense I. arambourgi I. gaudryi I. hipparionum I. orbingyi I. sinence I. preforfex †Thalassictis T. robusta †Hyaenotherium †Miohyaenotherium †Lychyaena †Tungurictis †Proictitherium Subfamily Hyaeninae †Palinhyaena †Ikelohyaena Hyaena H. brunnea, Brown Hyena H. hyaena, Striped Hyena †Hyaenictis †Leecyaena †Chasmaporthetes Chasmaporthetes lunensis Chasmaporthetes ossifragus Chasmaporthetes honanensis Chasmaporthetes borissiaki Chasmaporthetes australis Chasmaporthetes exitelus †Pachycrocuta †Adcrocuta Crocuta Crocuta crocuta, Spotted Hyena Subfamily Protelinae Proteles P. cristata, Aardwolf