The Casuariiformes is an order of large flightless birds that has four surviving members: the three

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

cassowary Cassowaries ( tpi, muruk, id, kasuari) are flightless birds of the genus ''Casuarius'' in the order Casuariiformes. They are classified as ratites (flightless birds without a keel on their sternum bones) and are native to the tropical forest ...

, and the only remaining species of

emu The emu () (''Dromaius novaehollandiae'') is the second-tallest living bird after its ratite relative the ostrich. It is endemic to Australia where it is the largest native bird and the only extant member of the genus ''Dromaius''. The emu' ...

. They are divided into either a single family,

Casuariidae The bird family Casuariidae has four surviving members: the three species of cassowary and the emu. All living members of the family are very large flightless birds native to Australia-New Guinea.Clements, J (2007) Species *† ''Emuarius'' Bol ...

, or more typically two, with the emu splitting off into its own family, Dromaiidae. All four living members are native to

Australia-New Guinea The continent of Australia, sometimes known in technical contexts by the names Sahul (), Australia-New Guinea, Australinea, Meganesia, or Papualand to distinguish it from the country of Australia, is located within the Southern and East ...

,Clements, J (2007) but some possible extinct taxa occurred in other landmasses.

Systematics and evolution

The emus form a distinct family, characterized by legs adapted for running. The total number of cassowary species described, based on minor differences in casque shape and color variations, formerly reached nine. Now, however, only three species are recognized, and most authorities only acknowledge few

subspecies In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (morphology), but that can successfully interbreed. Not all species ...

or none at all. The fossil record of casuariforms is interesting, but not very extensive. Regarding fossil species of ''

Dromaius ''Dromaius'' (from greek δρομαίυς "runner") 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 Vi ...

'' and ''

Casuarius Cassowaries ( tpi, muruk, id, kasuari) are flightless birds of the genus ''Casuarius'' in the order Casuariiformes. They are classified as ratites (flightless birds without a keel on their sternum bones) and are native to the tropical forest ...

'', see their genus pages. As with all

ratite A ratite () is any of a diverse group of flightless, large, long-necked, and long-legged birds of the infraclass Palaeognathae. Kiwi, the exception, are much smaller and shorter-legged and are the only nocturnal extant ratites. The systematics ...

s, there are several contested theories concerning their evolution and relationships. Some Australian fossils initially believed to be from emus were recognized to represent a distinct genus, ''Emuarius'',"Emuarius" is from "Emu" + "''Casuarius''". Describer W.E. Boles commonly refers to the genus as "emuwaries" or "cassomus". which had a cassowary-like skull and

femur The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates with ...

and an emu-like lower leg and foot. In addition, the first fossils of

mihirung Dromornithidae, known as mihirungs and informally as thunder birds or demon ducks, were a clade of large, flightless Australian birds of the Oligocene through Pleistocene Epochs. All are now extinct. They were long classified in Struthioniformes, ...

s were initially believed to be from giant emus,The vernacular name "mihirung" is derived from ''mihirung paringmal'', which means "giant emu" in the Chaap Wuurong language. but these birds were completely unrelated. It has been suggested that the

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...

n genus ''

Diogenornis ''Diogenornis'' is an extinct genus of ratites, that lived during the Eocene, Early Eocene (Itaboraian to Casamayoran in the South American land mammal age, SALMA classification).rheas The rheas ( ), also known as ñandus ( ) or South American ostriches, are large ratites (flightless birds without a keel on their sternum bone) in the order Rheiformes, native to South America, distantly related to the ostrich and emu. Most taxo ...

, the current South American lineage of giant ground birds. If this were the case, not only would it extend the fossil range of this lineage to a wider region, but to a broader time span as well, since ''Diogenornis'' occurs in the late

Paleocene The Paleocene, ( ) or Palaeocene, is a geological epoch (geology), epoch that lasted from about 66 to 56 mya (unit), million years ago (mya). It is the first epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), E ...

and is among the earliest known ratites. In the late 19th century, a fossil casuariid (''

Hypselornis ''Hypselornis'' is an extinct genus of fossil reptile, most likely a crocodilian, from the late Pliocene of India. Known only from a single toe bone, ''Hypselornis'' was originally mistakenly identified as a ratite bird related to the living cass ...

'') was named from India based on a single toe bone, however it was later shown to belong to a crocodilian. An especially interesting question regarding this order is whether emus or cassowaries are the more primitive form, if either. Emus are generally assumed to retain more ancestral features, in part because of their more modest coloration, but this does not necessarily have to be the case. The casuariiform fossil record is ambiguous, and the present knowledge of their

genome In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding ge ...

is insufficient for comprehensive analysis. Resolving the cladistic issues will require combination of all these approaches, with at least the additional consideration of

plate tectonics Plate tectonics (from the la, label=Late Latin, tectonicus, from the grc, τεκτονικός, lit=pertaining to building) is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of large ...

Taxonomy

Casuariiformes (Sclater, 1880) Forbes 1884Mikko's Phylogeny Archiv

Paleofile.com (net, info) .
*?†''

Diogenornis ''Diogenornis'' is an extinct genus of ratites, that lived during the Eocene, Early Eocene (Itaboraian to Casamayoran in the South American land mammal age, SALMA classification).Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...

) **†''

Diogenornis fragilis ''Diogenornis'' is an extinct genus of ratites, that lived during the Early Eocene (Itaboraian to Casamayoran in the SALMA classification).Casuariidae The bird family Casuariidae has four surviving members: the three species of cassowary and the emu. All living members of the family are very large flightless birds native to Australia-New Guinea.Clements, J (2007) Species *† ''Emuarius'' Bol ...

Kaup, 1847 asuariinae Reichenbach, 1849(emus and cassowaries) **†''

Emuarius ''Emuarius'' is an extinct genus of casuariiform 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 ''Emua ...

'' Boles, 1992 (emuwaries) (Late Oligocene – Late Miocene) ***†'' E. gidju'' (Patterson & Rich 1987) Boles, 1992 'Dromaius gidju'' Patterson & Rich 1987***†'' E. guljaruba'' Boles, 2001 **''

'' (Linnaeus 1758) Brisson, 1760

Cela Cela may refer to: People * Cela (surname), a Spanish-Galician surname * Çela, an Albanian surname * Ćela, nickname of Stevan Nedić (1875–1923), Serbian Chetnik commander in Old Serbia and Macedonia Placenames and jurisdictions Spain ...

'' Oken, 1816; '' Cela Cela may refer to: People * Cela (surname), a Spanish-Galician surname * Çela, an Albanian surname * Ćela, nickname of Stevan Nedić (1875–1923), Serbian Chetnik commander in Old Serbia and Macedonia Placenames and jurisdictions Spain ...

Systematics and evolution

Taxonomy

Footnotes

References

References

External links