| Physeteroidea | |
|---|---|
 A Sperm Whale and her calf | |
| Scientific Classification | |
| Kingdom | Animalia |
| Phylum | Chordata |
| Class | Mammalia |
| Order | Cetacea |
Physeteroidea is a superfamily including just three living species of whale; the sperm whale, in the genus Physeter, and the pygmy sperm whale and dwarf sperm whale, in the genus Kogia. In the past, these genera have sometimes been united in a single family, Physeteridae, with the two Kogia species in a subfamily (Kogiinae); however, recent practice is to allocate the genus Kogia to its own family, Kogiidae, leaving Physeteridae as a monotypic (single extant species) family.The earliest sperm whale fossils are known from the late Oligocene – about 25 million years ago, with an ancestry tracing back from the latest Eocene before diverging from the remainder of the Odontocetid line, leading to the dolphins, and porpoises.
Characteristics[]
The sperm whale (Physeter macrocephalus) is the largest species of toothed whale, with adult bulls (males) growing to be about 15–18 metres (49–59 ft) long, and weighing about 45–70 metric tons (44–69 long tons; 50–77 short tons). The two kogiid species are much smaller, at only around 2.5 to 3.5 metres (8 ft 2 in to 11 ft 6 in) in length, and weighing 350–500 kilograms (770–1,100 lb).
The bodies of physeteroids are robustly proportioned, with paddle-shaped flippers. The lower jaw is always relatively small and thin relative to the upper jaw. The nasal bones of these whales are distinctly asymmetrical, with the blowhole being located on the left side of the head; in the sperm whale this is near the top of the head, while on the kogiids it is further forward. All species have a large number of similar, and relatively simple, teeth. In the kogiids, and sometimes also in the sperm whale, the teeth in the upper jaw do not erupt, and are sometimes altogether absent.
The eyes of physeteroids are unable to swivel in their sockets, and possess only a vestigial anterior chamber. It is likely that echolocation is a far more important sense to these animals than vision.
Another common characteristic is the spermaceti, a semi-liquid waxy white substance filling the 'case' or spermaceti organ in the whale's head, which is thought to be involved in providing ballast for diving and maintaining buoyancy. This may be done by flushing cold water through the nose, hardening the spermaceti, to dive, and pumping warm blood to melt the spermaceti to surface. All three species dive to great depths to find food, although the sperm whale is believed to dive much deeper than either of the kogiids. Members of both families eat squid, fish, and even sharks.
Gestation lasts from nine to fifteen months, depending on species. The single calf remains with the mother for at least two years, before being weaned. Physeteroids do not reach full sexual maturity for several years. All species congregate in 'pods' or herds, consisting of mostly females, calfs, and adolescent males, although these pod sizes are typically smaller in the kogiids.
Families and Genera[]
Superfamily Physeteroidea
Genus Diaphorocetus† Genus Acrophyseter† A. deinodon Genus Zygophyseter† Z. varolai Genus Brygmophyseter† B. shigensis Genus Aulophyseter† A. morricei A. mediatlanticus A. rionegrensis Genus Livyatan†
Family Physeteridae
Genus Physeter Physeter macrocephalus, Sperm Whale Genus Orycterocetus† Genus Ferecetotherium† Genus Helvicetus † Genus Idiorophus † Genus Placoziphius † Genus Idiophyseter † Genus Physeterula † P. dubusi
Family Kogiidae
Genus Kogia Kogia breviceps, Pygmy Sperm Whale Kogia sima, Dwarf Sperm Whale Kogia pusilla† Genus Aprixokogia† Genus Kogiopsis† K. floridana Genus Praekogia† Genus Scaphokogia†
