Physeteroidea Temporal range:Oligocene torecent25–0 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Social group of thesperm whale,Physeter macrocephalus
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Artiodactyla
Infraorder:	Cetacea
Parvorder:	Odontoceti
Superfamily:	Physeteroidea Gray 1868
Families
Physeteridae Kogiidae

Physeteroidea is asuperfamily that includes threeextant species ofwhales: thesperm whale, in the genusPhyseter, and thepygmy sperm whale anddwarf sperm whale, in the genusKogia. In the past, these genera have sometimes been united in a single family, thePhyseteridae, with the twoKogia species in the subfamily Kogiinae; however, recent practice is to allocate the genusKogia to its own family, theKogiidae, leaving the Physeteridae as amonotypic (single extant species) family, althoughadditional fossil representatives of both families are known.

The sperm whale (Physeter macrocephalus) is the largest species oftoothed whale, with adult bulls (males) growing to be about 15–18 m (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, around 2.5 to 3.5 m (8 ft 2 in to 11 ft 6 in) in length, and weighing 350–500 kg (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. Thenasal bones of these whales are distinctly asymmetrical, with theblowhole 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.^[1]

The eyes of physeteroids are unable to swivel in their sockets, and possess only a vestigialanterior chamber.Echolocation likely is a far more important sense to these animals thanvision.^[1]

Another common characteristic is thespermaceti, a semiliquid waxy white substance filling the 'case' or spermaceti organ in the whale's head, which plays a primary role in the production and directional manipulation of focused clicking sounds used for echolocation in the extant great sperm whale (Physeter macrocephalus).^[2] 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 9 to 15 months, depending on species. The singlecalf remains with the mother for at least two years, before beingweaned. Physeteroids do not reach full sexual maturity for several years. All species congregate in 'pods' or herds, consisting of mostly females, calves, and adolescent males, although these pod sizes are typically smaller in the kogiids.^[1]

The earliest sperm whale fossils are known from the lateOligocene – about 25 million years ago,^[3][4] with an ancestry tracing back from the latestEocene before diverging from the remainder of the odontocetid line, leading to thedolphins, andporpoises.

Thefossil record suggests that sperm whales were more common in theMiocene, during which basal lineages (such asZygophyseter andBrygmophyseter) existed; other fossil genera assigned to the Physeteridae includeFerecetotherium,Helvicetus,Idiorophus,Diaphorocetus,Aulophyseter,Orycterocetus,Scaldicetus, andPlacoziphius, while kogiid fossil genera includeKogiopsis,Scaphokogia, andPraekogia.^[4] The earliest kogiids are known from the late Miocene, around 7 million years ago.^[5]

The close relationship between extant Physeteridae andKogiidae is confirmed in recent molecular studies using mitochondrial cytochromeb,;^[6][7] on the basis of these analyses, their nearest relatives appear to be theZiphiidae on one hand, and theMysticeti andPlatanistidae on the other. The last cited paper also favours the grouping of Physeteridae and Kogiidae in a single superfamily,Physeteroidea, as has sometimes previously been suggested. Bianucci & Landini, 2006^[8] suggest thatDiaphorocetus,Zygophyseter,Naganocetus, andAulophyseter antedate the inferred split of the Kogiidae and Physeteridae, thus would restrict the family Physeteridae to those genera that postdate this split (acladistic view).

They are members of theOdontoceti, thesuborder containing all the toothed whales and dolphins. Suggestions that the sperm whales might be a sister group to the baleen whales were refuted by molecular and morphological data, confirming the monophyly of Odontoceti including sperm whales.^[9] One extant species of the genusPhyseter is placed in the family Physeteridae. Two species of the related extant genusKogia, thepygmy sperm whaleK. breviceps and thedwarf sperm whaleK. simus, are sometimes also placed in this family, or else are placed in their own family, theKogiidae.^[10]

A summary of the classification of extant and extinct (†) taxa is:

• Physeteroidea, sperm whales
  • Stem physeteroids^[11]
    • †Acrophyseter
    • †Albicetus
    • †Aulophyseter
    • †Brygmophyseter (=Naganocetus)
    • †Diaphorocetus
    • †Eudelphis
    • †Livyatan^[12]
    • †Miophyseter^[13]
    • †Orycterocetus
    • †Rhaphicetus^[14]
    • †Zygophyseter
  • Physeteridae, sperm whales
    • †Cozzuoliphyseter^[15]
    • †Ferecetotherium^{[citation needed]}
    • †Helvicetus^{[citation needed]}
    • †Idiophyseter
    • †Idiorophus
    • †Orycterocetus
    • Physeter, sperm whales
      • Physeter macrocephalus, sperm whale
    • †Physeterula
    • †Placoziphius^[11]
    • †Preaulophyseter^[16]
    • †Scaldicetus
  • Kogiidae
    • †Aprixokogia
    • Kogia, small sperm whales
      • Kogia breviceps, pygmy sperm whale
      • Kogia sima, dwarf sperm whale
      • †Kogia pusilla
    • †Kogiopsis
    • †Praekogia
    • †Scaphokogia
    • †Thalassocetus^[17]

• †Eucetus
• †Graphiodon
• †Homocetus
• †Hoplocetus
• †Orcopsis
• †Palaeodelphis
• †Paleophoca
• †Physetodon
• †Physodon
• †Physotherium
• †Priscophyseter
• †Prophyseter
• †Scaptodon
• †Ziphoides

Wikispecies has information related toPhyseteroidea.

• Physeteroidea
• Toothed whales
• Extant Chattian first appearances
• Taxa named by John Edward Gray

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