Casuariidae
Encyclopedia
The bird family Casuariidae has four surviving members: the three species
of cassowary
, and the only remaining species of Emu
. The emus were formerly classified in their own family, Dromaiidae, but are regarded as sufficiently closely related to the cassowaries to be part of the same family.
All four members of the family are very large flightless birds native to Australia-New Guinea. The characteristics of the family are those of its members.
s, there are several contested theories concerning their evolution and relationships. As regards this family, it is especially interesting whether emus or cassowaries are the more primitive form: the latter are generally assumed to retain more plesiomorphic features, but this does not need to be true at all; the fossil record is also ambiguous, and the present state of genomics
does not allow for sufficiently comprehensive analyses. A combination of all these approaches with considerations of plate tectonics
at least is necessary for resolving this issue.
The number of cassowary species described based on minor differences in casque shape and color variations is quite large. In recent times, however, only 3 species are recognized, and most authorities only acknowledge few subspecies
or none at all.
The fossil record of casuariforms is interesting, but not very extensive. Regarding fossil species of Dromaius and Casuarius, see their genus pages.
Some Australian fossils initially believed to be from emus were recognized to represent a distinct genus, Emuarius,
which had a cassowary-like skull and femur
and an emu-like lower leg and foot. In addition, the first fossils of mihirungs were initially believed to be from giant emus,
but these birds were completely unrelated.
Subfamily Casuariinae - cassowaries
Subfamily Dromaiinae - emus
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of cassowary
Cassowary
The cassowaries are ratites, very large flightless birds in the genus Casuarius native to the tropical forests of New Guinea, nearby islands and northeastern Australia. There are three extant species recognized today...
, and the only remaining species of Emu
Emu
The Emu Dromaius novaehollandiae) is the largest bird native to Australia and the only extant member of the genus Dromaius. It is the second-largest extant bird in the world by height, after its ratite relative, the ostrich. There are three subspecies of Emus in Australia...
. The emus were formerly classified in their own family, Dromaiidae, but are regarded as sufficiently closely related to the cassowaries to be part of the same family.
All four members of the family are very large flightless birds native to Australia-New Guinea. The characteristics of the family are those of its members.
Systematics and evolution
The emus form a distinct subfamily, characterized by legs adapted for running. As with all ratiteRatite
A ratite is any of a diverse group of large, flightless birds of Gondwanan origin, most of them now extinct. Unlike other flightless birds, the ratites have no keel on their sternum—hence the name from the Latin ratis...
s, there are several contested theories concerning their evolution and relationships. As regards this family, it is especially interesting whether emus or cassowaries are the more primitive form: the latter are generally assumed to retain more plesiomorphic features, but this does not need to be true at all; the fossil record is also ambiguous, and the present state of genomics
Genomics
Genomics is a discipline in genetics concerning the study of the genomes of organisms. The field includes intensive efforts to determine the entire DNA sequence of organisms and fine-scale genetic mapping efforts. The field also includes studies of intragenomic phenomena such as heterosis,...
does not allow for sufficiently comprehensive analyses. A combination of all these approaches with considerations of plate tectonics
Plate tectonics
Plate tectonics is a scientific theory that describes the large scale motions of Earth's lithosphere...
at least is necessary for resolving this issue.
The number of cassowary species described based on minor differences in casque shape and color variations is quite large. In recent times, however, only 3 species are recognized, and most authorities only acknowledge few subspecies
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
or none at all.
The fossil record of casuariforms is interesting, but not very extensive. Regarding fossil species of Dromaius and Casuarius, see their genus pages.
Some Australian fossils initially believed to be from emus were recognized to represent a distinct genus, Emuarius,
which had a cassowary-like skull and femur
Femur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...
and an emu-like lower leg and foot. In addition, the first fossils of mihirungs were initially believed to be from giant emus,
but these birds were completely unrelated.
Subfamily Casuariinae - cassowaries
- Genus Casuarius
- Southern CassowarySouthern CassowaryThe Southern Cassowary, Casuarius casuarius, also known as Double-wattled Cassowary, Australian Cassowary or Two-wattled Cassowary, is a large flightless black bird...
, Casuarius casuarius located in the humid forests of northeastern AustraliaAustraliaAustralia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
, New GuineaNew GuineaNew Guinea is the world's second largest island, after Greenland, covering a land area of 786,000 km2. Located in the southwest Pacific Ocean, it lies geographically to the east of the Malay Archipelago, with which it is sometimes included as part of a greater Indo-Australian Archipelago...
, and the Aru IslandsAru IslandsThe Aru Islands are a group of about ninety-five low-lying islands in the Maluku province of eastern Indonesia. They also form a regency of Indonesia.-Geography:...
. - Dwarf CassowaryDwarf CassowaryThe Dwarf Cassowary, Casuarius bennetti, also known as the Bennett's Cassowary, Little Cassowary, Mountain Cassowary, or Mooruk, is the smallest of the three species of cassowaries.-Taxonomy:...
, Casuarius bennetti located in New GuineaNew GuineaNew Guinea is the world's second largest island, after Greenland, covering a land area of 786,000 km2. Located in the southwest Pacific Ocean, it lies geographically to the east of the Malay Archipelago, with which it is sometimes included as part of a greater Indo-Australian Archipelago...
, New BritainNew BritainNew Britain, or Niu Briten, is the largest island in the Bismarck Archipelago of Papua New Guinea. It is separated from the island of New Guinea by the Dampier and Vitiaz Straits and from New Ireland by St. George's Channel...
, and Yapen Island. - Northern CassowaryNorthern CassowaryThe Northern Cassowary, Casuarius unappendiculatus, also known as the Single -wattled Cassowary or Gold-neck Cassowary, is a large, stocky flightless bird.-Taxonomy:...
, Casuarius unappendiculatus located in the lowlands of Yapen Island and New GuineaNew GuineaNew Guinea is the world's second largest island, after Greenland, covering a land area of 786,000 km2. Located in the southwest Pacific Ocean, it lies geographically to the east of the Malay Archipelago, with which it is sometimes included as part of a greater Indo-Australian Archipelago...
. - †Casuarius lydekki
- Southern Cassowary
Subfamily Dromaiinae - emus
- Genus DromaiusDromaiusDromaius is a genus of ratite present in Australia. There is one extant species, Dromaius novaehollandiae commonly known as the Emu.In his original 1816 description of the emu, Louis Jean Pierre Vieillot used two generic names; first Dromiceius, then Dromaius a few pages later...
- EmuEmuThe Emu Dromaius novaehollandiae) is the largest bird native to Australia and the only extant member of the genus Dromaius. It is the second-largest extant bird in the world by height, after its ratite relative, the ostrich. There are three subspecies of Emus in Australia...
, Dromaius novaehollandiae located in AustraliaAustraliaAustralia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
.- †Tasmanian EmuTasmanian EmuThe Tasmanian Emu is an extinct subspecies of the Emu. It was found on Tasmania where it had become isolated during the Late Pleistocene...
, D. n. diemenensis (extinct) formerly located in TasmaniaTasmaniaTasmania is an Australian island and state. It is south of the continent, separated by Bass Strait. The state includes the island of Tasmania—the 26th largest island in the world—and the surrounding islands. The state has a population of 507,626 , of whom almost half reside in the greater Hobart...
. - South Eastern Emu, D. n. novaehollandiae located in AustraliaAustraliaAustralia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
. - South Western Emu, D. n. rothschildi
- Northern Emu D. n. woodwardi
- †King Island EmuKing Island EmuThe King Island Emu or Black Emu is an extinct sub-species of emu which occurred on King Island between mainland Australia and Tasmania. It is known from 19th century descriptions of live birds, as well as subfossil bones and one museum specimen...
, D. n. ater (extinct) formerly located on King Island, Australia.
- †Tasmanian Emu
- †Kangaroo Island EmuKangaroo Island EmuKangaroo Island Emu or Dwarf Emu is an extinct member of the bird family Casuariidae. It was restricted to Kangaroo Island, South Australia, which was known as Ile Decrés by the members of the Baudin expedition. It differed from the mainland Emu mainly in its smaller size...
, Dromaius baudinianus (extinct) - †Dromaius ocypus
- Emu
- Genus EmuariusEmuariusEmuarius is an extinct genus of flightless bird from Australia that lived during the early Miocene and late Oligocene. It is one of two known genera of emu. There are two known species in the genus, Emuarius gidju and Emuarius guljaruba. The birds in this genus are known as emuwaries...
- "emuwaries" (fossilFossilFossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
)- †Emuarius guljaruba (Late OligoceneOligoceneThe Oligocene is a geologic epoch of the Paleogene Period and extends from about 34 million to 23 million years before the present . As with other older geologic periods, the rock beds that define the period are well identified but the exact dates of the start and end of the period are slightly...
- Late MioceneMioceneThe Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...
) - †Emuarius gidju (Late Oligocene - Early Miocene of N Australia - see: Records of the Australian Museum (2005) Vol. 57: 179)
- †Emuarius guljaruba (Late Oligocene