Dromornis Planei
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''Dromornis'' is a
genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
of large to enormous
prehistoric birds Late Quaternary prehistoric birds are Bird, avian taxa that became extinct during the Late Quaternary – the Late Pleistocene or Early Holocene – and before recorded history, specifically before they could be studied alive by orni ...
native to Australia during the
Oligocene The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...
to
Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58Dromornithidae Dromornithidae, known as mihirungs (after Tjapwuring ''Mihirung paringmal'', "giant bird") and informally as thunder birds or demon ducks, were a clade of large, flightless Australian birds of the Oligocene through Pleistocene epochs. All are no ...
, extinct flightless birds known as mihirungs.


Taxonomy

The genus was erected to separate a new species, '' Dromornis australis'', from the previously described ''
Dinornis The giant moa (''Dinornis'') is an extinct genus of birds belonging to the moa family. As with other moa, it was a member of the order Dinornithiformes. It was endemic to New Zealand. Two species of ''Dinornis'' are considered valid, the Nort ...
'' (giant moas), another lineage of ancient large and flightless birds found in New Zealand that was earlier described by
Richard Owen Sir Richard Owen (20 July 1804 – 18 December 1892) was an English biologist, comparative anatomy, comparative anatomist and paleontology, palaeontologist. Owen is generally considered to have been an outstanding naturalist with a remarkabl ...
in 1843. A femur that was forwarded to England, probably a dromornithid and since lost, suggested an Australian genus, but Owen withheld publication for many years. The type specimen, another femur, was found in a well at
Peak Downs Peak Downs is a geographic area, and formerly a station, in the vicinity of Clermont, Central Queensland. In the 1860s and 1870s the area was known as "the Peak Downs". The morphology of this region consisted of numerous distinct peaks of bas ...
,
Queensland Queensland ( , commonly abbreviated as Qld) is a States and territories of Australia, state in northeastern Australia, and is the second-largest and third-most populous state in Australia. It is bordered by the Northern Territory, South Austr ...
, and subsequently described by Owen in 1872.Murray, P. F. Vickers-Rich, P. (2004) Magnificent Mihirungs: The Colossal Flightless Birds of the Australian Dreamtime. Indiana University Press. . Owen's new taxon was published in a series on prehistoric birds, read before the
Zoological Society of London The Zoological Society of London (ZSL) is a charity and organization devoted to the worldwide animal conservation, conservation of animals and their habitat conservation, habitats. It was founded in 1826. Since 1828, it has maintained London Zo ...
then appearing in its ''Transactions''. The name of the genus is derived from Ancient Greek, ''dromos'' meaning running, a race, and ''ornitho'', a bird.Rich, P.V. 1979
The Dromornithidae, a family of large,extinct ground birds endemic to Australia: Systematic and phylogenetic considerations
Canberra Bureau of Mineral Resources, Geology and Geophysics Bulletin 184, 1–196.
The genus and family are referred to as mihirung, distinguishing these birds from the giant emus. 'Mihirung paringmal' is an Aboriginal word from the
Tjapwuring The Djab Wurrung, also spelt Djabwurrung, Tjapwurrung, Tjap Wurrung, or Djapwarrung, people are Aboriginal Australians whose country is the volcanic plains of central Victoria from the Mount William Range of Gariwerd in the west to the Pyrenee ...
people of Western Victoria and it means 'giant bird'. The placement of these dromornithid species may be summarised as
Dromornithidae Dromornithidae, known as mihirungs (after Tjapwuring ''Mihirung paringmal'', "giant bird") and informally as thunder birds or demon ducks, were a clade of large, flightless Australian birds of the Oligocene through Pleistocene epochs. All are no ...
(8 extinct species in 4 genera) * ''Dromornis'' :* ''Dromornis australis''
Owen Owen may refer to: People and fictional characters * Owen (name), including a list of people and fictional characters with the given name or surname Places United States * Owen, Missouri, a ghost town * Owen, Wisconsin * Owen County, Indiana ...
, 1872 :* ''Dromornis murrayi'' Worthy ''et al.'', 2016 :* ''Dromornis planei'' (''Bullockornis planei''
Rich Rich may refer to: Common uses * Rich, an entity possessing wealth * Rich, an intense taste, flavor, color, sound, texture, or feeling **Rich (wine), a descriptor in wine tasting Places United States * Rich, Mississippi, an unincorporated c ...
, 1979) :* ''Dromornis stirtoni'' Rich, 1979 * ''
Barawertornis ''Barawertornis'' is an extinct genus of cassowary-sized dromornithid known from Oligocene and Miocene deposits in Queensland and South Australia. Only a single species, ''B. tedfordi'', is placed in this genus. It shows adaptations towards a cur ...
'' * ''
Ilbandornis ''Ilbandornis'' was a genus of ostrich-sized dromornithid, a clade known casually as "demon ducks" because they are most closely related to the water fowl clade anseriformes. It was far more lightly built than other members of the family, indicat ...
'' * ''
Genyornis ''Genyornis newtoni'' is an extinct species of large, flightless bird that lived in Australia during the Pleistocene Epoch until around 50,000 years ago. Over two metres in height, they were likely herbivorous. Many other species of Austral ...
'' The ''Dromornis'' lineage is proposed to represent a monotypic succession, from earliest to latest these are ''D. murrayi, D. planei, D. stirtoni'', and this species, ''D. australis''. The dromornithid family are sometimes known by appellations such as Stirton's mihirung (''D. stirtoni'') to refer to each species. Nicknames describing the species as 'thunderbirds' etc. have appeared in reports of their discovery, later terms such as "demon ducks" refer to their relationship to the extant waterfowl of the galloanseres.


Description

''Dromornis'' is a genus of large to gigantic flightless birds of the
Dromornithidae Dromornithidae, known as mihirungs (after Tjapwuring ''Mihirung paringmal'', "giant bird") and informally as thunder birds or demon ducks, were a clade of large, flightless Australian birds of the Oligocene through Pleistocene epochs. All are no ...
family. Members of this family lived from 8 million years ago until less than 30,000 years ago. Although they looked like giant
emu The emu (; ''Dromaius novaehollandiae'') is a species of flightless bird endemism, endemic to Australia, where it is the Tallest extant birds, tallest native bird. It is the only extant taxon, extant member of the genus ''Dromaius'' and the ...
s, ''Dromornis'' and its relatives are more closely related to the earliest waterfowl of the
Anseriformes Anseriformes is an order (biology), order of birds also known as waterfowl that comprises about 180 living species of birds in three families: Anhimidae (three species of screamers), Anseranatidae (the magpie goose), and Anatidae, the largest f ...
order or a basal
galliform Galliformes is an order (biology), order of heavy-bodied ground-feeding birds that includes turkey (bird), turkeys, chickens, Old World quail, quail, and other landfowl. Gallinaceous birds, as they are called, are important in their ecosystems ...
. Comparative studies using endocranial reconstructions of dromornithids, ''
Ilbandornis ''Ilbandornis'' was a genus of ostrich-sized dromornithid, a clade known casually as "demon ducks" because they are most closely related to the water fowl clade anseriformes. It was far more lightly built than other members of the family, indicat ...
'' and three ''Dromornis'' species, suggest that the head and bill of the ''Dromornis'' lineage became foreshortened. The species resemble large birds of the Northern hemisphere, the
Paleognathae Palaeognathae (; ) is an infraclass of birds, called paleognaths or palaeognaths, within the class Aves of the clade Archosauria. It is one of the two extant infraclasses of birds, the other being Neognathae, both of which form Neornithes. Pala ...
s, of whom some descendants are known as ostriches and their allies. Like those
ratites Ratites () are a polyphyletic group consisting of all birds within the infraclass Palaeognathae that lack keel (bird anatomy), keels and flightless bird, cannot fly. They are mostly large, long-necked, and long-legged, the exception being the Kiw ...
who also evolved alongside mammals, the diversity of species was very low, apparently monotypes that emerged in succession and increased in size. ''Dromornis stirtoni'' is amongst the largest known birds, although ''
Aepyornis maximus ''Aepyornis'' is an extinct genus of elephant bird formerly Endemism, endemic to Madagascar. The genus had two species, the smaller ''A. hildebrandti'' and the larger ''A. maximus'', which is possibly the largest bird ever to have lived. Its clo ...
'', a species of
elephant bird Elephant birds are extinct flightless birds belonging to the Order (biology), order Aepyornithiformes that were native to the island of Madagascar. They are thought to have gone extinct around 1000 CE, likely as a result of human activity. Eleph ...
from Madagascar, were likely just as heavy, if not heavier. The height of ''D. stirtoni'' would probably have met or exceeded the females of the tallest species of the genus ''
Dinornis The giant moa (''Dinornis'') is an extinct genus of birds belonging to the moa family. As with other moa, it was a member of the order Dinornithiformes. It was endemic to New Zealand. Two species of ''Dinornis'' are considered valid, the Nort ...
'', the giant
moa Moa are extinct giant flightless birds native to New Zealand. Moa or MOA may also refer to: Arts and media * Metal Open Air, a Brazilian heavy metal festival * MOA Museum of Art in Japan * The Moas, New Zealand film awards People * Moa ...
of New Zealand. (Some moa exhibited
sexual dimorphism Sexual dimorphism is the condition where sexes of the same species exhibit different Morphology (biology), morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecy, di ...
, with females tending to be larger than males.)


Species


''D. australis''

''Dromornis australis'' fossils are found in
Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...
. They were once considered the smallest species of the genus ''Dromornis'', around three quarters the size of ''
Dromornis stirtoni ''Dromornis'' is a genus of large to enormous Fossil birds, prehistoric birds native to Australia during the Oligocene to Pliocene epochs. The species were flightless, possessing greatly reduced wing structures but with large legs, similar to the ...
'', until the discovery of '' Dromornis planei'' specimens were described in 2016.


Discovery

The fossil remains of a large femur were discovered at
Peak Downs Peak Downs is a geographic area, and formerly a station, in the vicinity of Clermont, Central Queensland. In the 1860s and 1870s the area was known as "the Peak Downs". The morphology of this region consisted of numerous distinct peaks of bas ...
in Queensland, at a depth of around in a well shaft. This type of locality was described as an assemblage of boulders and pebbles beneath around thirty feet of alluvial soil; the femur was located over a boulder in the rock beds. The description of ''Dromornis australis'' by Richard Owen, best known for extensive work on the paleontology of Australian mammals, was the first of an extinct Australian avian species. Owen had previously sought evidence of ''
Dinornis The giant moa (''Dinornis'') is an extinct genus of birds belonging to the moa family. As with other moa, it was a member of the order Dinornithiformes. It was endemic to New Zealand. Two species of ''Dinornis'' are considered valid, the Nort ...
'' in the palaeontological collections of early Australian excavations. A femur that he had noted in the appendix of Thomas Mitchell's explorations, found in a cave, did not allow him to confirm an alliance with any previously described species of large flightless birds. Owen withheld describing that specimen, now thought lost, until the type for this species emerged many years later. The new material had been found while digging a well at Peak Downs and forwarded to Owen via W. B. Clarke, a geologist employed by the state of New South Wales, with a remark by
Gerard Krefft Johann Ludwig (Louis) Gerard Krefft (17 February 1830 – 18 February 1881), was an Australian artist, draughtsman, scientist, and natural historian who served as the curator of the Australian Museum for 13 years (1861–1874). He was one of A ...
that placed it with the New Zealand
moa Moa are extinct giant flightless birds native to New Zealand. Moa or MOA may also refer to: Arts and media * Metal Open Air, a Brazilian heavy metal festival * MOA Museum of Art in Japan * The Moas, New Zealand film awards People * Moa ...
s of ''Dinornis''. Richard Owen found affinities and distinctions in an osteological comparison to species of the extinct ''Dinornis'' and the extant ''
Dromaius ''Dromaius'' (from greek language, 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, Lou ...
'' (the emu) and proposed that it represented a new genus.


Description

The species is known by the right femur, around twelve inches long, obtained at the Peak Downs site. The details of its deposition accompanied Owen's description, "The well was sunk through 30 feet of the black trappean alluvial soil common in that part of Australia, and then through 150 feet of drift pebbles and boulders, on one of which boulders ("at that depth," 150 feet?) rested a short, thick femur, so filled with mineral matter (calc spar and iron pyrites) as to give the internal structure more the appearance of a reptilian than an ornithic bone." Owen notes the specimen was reported by W. B. Clarke, attributing it to ''Dinornis'', in the ''
Geological Magazine The ''Geological Magazine'' is a peer-reviewed scientific journal established in 1864, covering the earth sciences. It publishes original scientific research papers on geological topics. The journal is published bimonthly by Cambridge University ...
'' several years before. The femur is similar in size to '' Ilbandornis woodburnei'', another dromornithid species. Other osteological features of the specimens have been compared to ''
Dromornis stirtoni ''Dromornis'' is a genus of large to enormous Fossil birds, prehistoric birds native to Australia during the Oligocene to Pliocene epochs. The species were flightless, possessing greatly reduced wing structures but with large legs, similar to the ...
'', the gigantic "Stirton's thunderbird". A comparative analysis that included this femur indicated morphological characters assignable to either ''Dromornis'' or a continuation of a ''Ilbandornis woodburnei'' lineage, allied to more gracile species of the family, but these results were not considered to be necessarily characteristic to any dromornithid genera. A fragment of
synsacrum The synsacrum is a skeletal structure of birds and other dinosaurs, pterosaurs, as well as xenarthran mammals, in which the sacrum is extended by incorporation of additional fused or partially fused caudal or lumbar In tetrapod anatomy, lum ...
found at the Canadian deep lead mine near
Gulgong Gulgong is a 19th-century gold rush town in the Central Tablelands and the wider Central West (New South Wales), Central West regions of the Australian States and territories of Australia, state of New South Wales. The town is situated within th ...
has been tentatively assigned to ''Dromornis'', the slight possibility that it is referable to this species might represent the continuation of the lineage as a smaller species into the Pliocene.


''D. murrayi''

''Dromornis murrayi'' was described in 2016 using specimens discovered amongst the
Riversleigh fauna Riversleigh fauna is the collective term for any species of animal identified in fossil sites located in the Riversleigh World Heritage Area. Faunal zones The presence of the Riversleigh in the Oligo-Miocene has been exceptionally well preserve ...
in Queensland, Australia. The period during which it existed was the Oligocene to early Miocene, making this the earliest known species of the genus ''Dromornis''. The size of these mihirungs was also determined to be the smallest of its genus. ''Dromornis murrayi'' was described from specimens of cranial and post cranial material. The type material is the partial remains of a cranium, which was obtained at a locality named Hiatus A Site in the Carl Creek Limestone Formation; this location is one of the numerous study sites at the
Riversleigh World Heritage Area Riversleigh World Heritage Area is Australia's most famous fossil location, recognised for the series of well preserved fossils deposited from the Late Oligocene to more recent geological periods. The fossiliferous limestone system is located n ...
. The specimens were discovered by two of the collaborating authors, Michael Archer and Suzanne J. Hand, the head researchers of taxa at the celebrated Riversleigh site and its associated fauna.


Description

This species stood around high and weighed up to , a considerable size but smaller than its congeners; the later species ''
Dromornis stirtoni ''Dromornis'' is a genus of large to enormous Fossil birds, prehistoric birds native to Australia during the Oligocene to Pliocene epochs. The species were flightless, possessing greatly reduced wing structures but with large legs, similar to the ...
'' is determined to have been up to . The fossil specimens used to describe ''Dromornis murrayi'' have been dated to 26 million years ago, being discovered at a 'shelf', a rich layer of fossilised bones, that included leg and cranial remains of the unknown species. Wings were greatly reduced, approximately , and would not have been evident beneath the bird's plumage. The skull cavity held an exceptionally small brain, the description's leading author Trevor Worthy suggesting the comparison, "I mean, if a chicken was silly, these things were very much more silly."


Distribution

The fossil deposits of ''Dromornis murrayi'' at the Hiatus site of Riversleigh have been dated as
early Miocene The Early Miocene (also known as Lower Miocene) is a sub-epoch of the Miocene epoch (geology), Epoch made up of two faunal stage, stages: the Aquitanian age, Aquitanian and Burdigalian stages. The sub-epoch lasted from 23.03 ± 0.05 annum, Ma to ...
and another as late
Oligocene The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...
to early Miocene. This was established using correlation with the evolutionary stage of vertebrate species known from other sites at Riversleigh. Hiatus site is limestone deposited in an aquatic setting, lacking indicators for methods such as radiometric dating. Another site where the species occurs is Cadbury's Kingdom, designated as Faunal Zone B which is also dated as early Miocene. The temporal range of these finds is approximately 25 to 16
mega-annum A year is a unit of time based on how long it takes the Earth to orbit the Sun. In scientific use, the tropical year (approximately 365 solar days, 5 hours, 48 minutes, 45 seconds) and the sidereal year (about 20 minutes longer) are more exa ...
. The only known occurrence of this species is amongst the
Riversleigh fauna Riversleigh fauna is the collective term for any species of animal identified in fossil sites located in the Riversleigh World Heritage Area. Faunal zones The presence of the Riversleigh in the Oligo-Miocene has been exceptionally well preserve ...
, the site is located in the northeastern region of the Australian continent.


''D. planei''

''Dromornis planei'', formerly placed in a separate genus ''Bullockornis'', lived in the Middle
Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...
, approximately 15 million years ago. It is known from specimens of the Bullock Creek fauna, fossils found in the Northern Territory of
Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...
. As large as an ostrich or emu, the species possessed a stocky build. A proposed common name, referring to its discoverer and locality, is Plane's bull bird. The site of its discovery was once semi-arid, containing low vegetation around seasonal wetlands and rivers. The species was first described by
Patricia Vickers-Rich Patricia Arlene Vickers-Rich (born 11 July 1944), also known as Patricia Rich, is an Australian Professor of Palaeontology and Palaeobiology, who researches the environmental changes that have impacted Australia (including the ancient super ...
in 1979, assigning it to a new genus ''Bullockornis''. The description's first generic epithet was derived by a partial reference to the Bullock Creek Site and the greek word for bird ''ornis'', and the common name bull bird proposed by the author for genus. The type is a fossilised section of the right femur, with other material, vertebrae and a rib, also referred to the same species. The specific epithet honours the discoverer of the vertebrae fossils, Michael Plane, thus the proposed trivial name of "Plane's Bull Bird". Plane had been the first to investigate the Bullock Creek site, details of which were published in a 1968 paper. It was one of several species of mihirungs, the
dromornithid Dromornithidae, known as mihirungs (after Tjapwuring ''Mihirung paringmal'', "giant bird") and informally as thunder birds or demon ducks, were a clade of large, flightless Australian birds of the Oligocene through Pleistocene epochs. All are no ...
s, that share ancestry with ducks and geese. The
nickname A nickname, in some circumstances also known as a sobriquet, or informally a "moniker", is an informal substitute for the proper name of a person, place, or thing, used to express affection, playfulness, contempt, or a particular character trait ...
"Demon Duck of Doom" is a reference to the large bill and body of the species. Fossil specimens of this species and other mihirungs are common, but the example of a near complete skull discovered in the 1980s was an unusual find. The direct evidence of the beak structure was evaluated in debate over the diet and habits of dromornithids. The bird's generic name is improperly translated as "ox-bird", but was named instead for the type locality for the genus at Bullock Creek,
Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...
. In 2010, Nguyen and Boles first suggested that ''Bullockornis'' represents another species of ''Dromornis'' on the basis of many common traits observed in the cranial and postcranial skeleton of both taxa and their close relationship strongly supported by their phylogenetic analyses. Subsequent studies also agreed upon placing this species within the genus ''Dromornis''. Some
paleontologist Paleontology, also spelled as palaeontology or palæontology, is the scientific study of the life of the past, mainly but not exclusively through the study of fossils. Paleontologists use fossils as a means to classify organisms, measure geolo ...
s, including Peter Murray of the Central Australian Museum, believe that ''Bullockornis'' was related to
geese A goose (: geese) is a bird of any of several waterfowl species in the family Anatidae. This group comprises the genera '' Anser'' (grey geese and white geese) and ''Branta'' (black geese). Some members of the Tadorninae subfamily (e.g., Egyp ...
and
duck Duck is the common name for numerous species of waterfowl in the family (biology), family Anatidae. Ducks are generally smaller and shorter-necked than swans and goose, geese, which are members of the same family. Divided among several subfam ...
s. This, in addition to the bird's tremendous size and earlier misclassification as a carnivore, gave rise to its colourful nickname. It may be somewhat inaccurate, however, as other studies have recovered dromornithids as more closely related to
Galliformes Galliformes is an order (biology), order of heavy-bodied ground-feeding birds that includes turkey (bird), turkeys, chickens, Old World quail, quail, and other landfowl. Gallinaceous birds, as they are called, are important in their ecosystems ...
. The existence of only this species at the Bullock Creek Site, as with the late Miocene Alcoota local fauna, correlates to the lack of diversity in large
ratite Ratites () are a polyphyletic group consisting of all birds within the infraclass Palaeognathae that lack keels and cannot fly. They are mostly large, long-necked, and long-legged, the exception being the kiwi, which is also the only nocturnal ...
s, such as the evolution of the ostriches in the presence of a diversity of mammals.


Description

''Dromornis planei'' was a very large flightless bird, similar in height to an
ostrich Ostriches are large flightless birds. Two living species are recognised, the common ostrich, native to large parts of sub-Saharan Africa, and the Somali ostrich, native to the Horn of Africa. They are the heaviest and largest living birds, w ...
or
emu The emu (; ''Dromaius novaehollandiae'') is a species of flightless bird endemism, endemic to Australia, where it is the Tallest extant birds, tallest native bird. It is the only extant taxon, extant member of the genus ''Dromaius'' and the ...
but with a heavier build; the species is however exceeded in size by the largest of these "thunder birds" ''Dromornis stirtoni''. Its bill was curved and deep, the overall size of the head and skull was remarkably large. The species stood approximately 2.5 metres (8 ft 2 in) tall. It may have weighed up to 250 kg (550 lb). Features of skull, including a very large
beak The beak, bill, or rostrum is an external anatomical structure found mostly in birds, but also in turtles, non-avian dinosaurs and a few mammals. A beak is used for pecking, grasping, and holding (in probing for food, eating, manipulating and ...
suited to shearing, have made some researchers consider that the bird may have been
carnivorous A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose nutrition and energy requirements are met by consumption of animal tissues (mainly mu ...
, but most currently agree that it was a
herbivore A herbivore is an animal anatomically and physiologically evolved to feed on plants, especially upon vascular tissues such as foliage, fruits or seeds, as the main component of its diet. These more broadly also encompass animals that eat ...
. The bird's skull is larger than that of small horses.Ellis, R. (2004) ''No Turning Back: The Life and Death of Animal Species''. New York: Harper Perennial. p. 102. . The species is presumed to have had greatly reduced wing structures, as with other flightless birds the
sternum The sternum (: sternums or sterna) or breastbone is a long flat bone located in the central part of the chest. It connects to the ribs via cartilage and forms the front of the rib cage, thus helping to protect the heart, lungs, and major bl ...
was not keeled. The exceptionally large legs of ''D. planei'' enabled it to move its great mass relatively quickly.


Habitat

A species known from the Bullock Creek fossil fauna in the
Northern Territory The Northern Territory (abbreviated as NT; known formally as the Northern Territory of Australia and informally as the Territory) is an states and territories of Australia, Australian internal territory in the central and central-northern regi ...
, the habitat during the time of deposition was a seasonally wet
floodplain A floodplain or flood plain or bottomlands is an area of land adjacent to a river. Floodplains stretch from the banks of a river channel to the base of the enclosing valley, and experience flooding during periods of high Discharge (hydrolog ...
and river. The flora probably consisted of sedges and shrubs favouring a semi-arid climate. The area was occupied by herbivores favoring shrubland, horned turtles, marsupial tapirs and
diprotodontid Diprotodontidae is an extinct Family (biology), family of large herbivorous marsupials, endemic to Australia and New Guinea during the Oligocene through Pleistocene periods from 28.4 million to 40,000 years ago. Description The family primaril ...
species, but the fauna associated with this site were rarely the forest dwelling paleospecies of the period. Other mihirungs also occur in the Bullock Creek fauna, species of ''
Ilbandornis ''Ilbandornis'' was a genus of ostrich-sized dromornithid, a clade known casually as "demon ducks" because they are most closely related to the water fowl clade anseriformes. It was far more lightly built than other members of the family, indicat ...
''. ''Dromornis planei'' remains are found with other large contemporaries, such as the diprotodont ''
Neohelos ''Neohelos'' is an extinct diprotodontid marsupial, that lived from the early to middle-Miocene. There are four species assigned to this genus, ''Neohelos tirarensis'', the type species, ''N. stirtoni'', ''N. solus'' and ''N. davidridei''. ''N. d ...
'', and the crocodiles ''
Baru ''Baru'', sometimes referred to as the cleaver-headed crocodile, is an extinct genus of Australian mekosuchine crocodilian. Its fossils have been found from various Late Oligocene and Miocene localities from across the Northern Territory and Que ...
'' that preyed upon them as they came to the water's edge. The diet of these birds is uncertain, although it is determined that the bill was thin and had little bite force.
Gastrolith A gastrolith, also called a stomach stone or gizzard stone, is a rock held inside a gastrointestinal tract. Gastroliths in some species are retained in the muscular gizzard and used to grind food in animals lacking suitable grinding teeth. In ...
s are found with similar species of other regions,
Genyornis ''Genyornis newtoni'' is an extinct species of large, flightless bird that lived in Australia during the Pleistocene Epoch until around 50,000 years ago. Over two metres in height, they were likely herbivorous. Many other species of Austral ...
, ''Ilbandornis'' and near relation ''
Dromornis stirtoni ''Dromornis'' is a genus of large to enormous Fossil birds, prehistoric birds native to Australia during the Oligocene to Pliocene epochs. The species were flightless, possessing greatly reduced wing structures but with large legs, similar to the ...
'', suggesting a herbivorous diet like the other species it is found alongside, yet suggestions have published that ''D. planei'' might have the carnivorous abilities attributed to the
terror birds Phorusrhacids, colloquially known as terror birds, are an extinct family of large carnivorous, mostly flightless birds that were among the largest apex predators in South America during the Cenozoic era. Their definitive fossil records range from ...
.


''D. stirtoni''

''Dromornis stirtoni'', colloquially known as Stirton's mihirung and Stirton's thunderbird, was a large feathered bird that grew up to heights of and weights in excess of 500 kg and is widely thought to have been the largest avian species to have ever existed.
Patricia Vickers-Rich Patricia Arlene Vickers-Rich (born 11 July 1944), also known as Patricia Rich, is an Australian Professor of Palaeontology and Palaeobiology, who researches the environmental changes that have impacted Australia (including the ancient super ...
first discovered the remains of the bird in 1979 in the Alcoota Fossil Beds in the
Northern Territory of Australia The Northern Territory (abbreviated as NT; known formally as the Northern Territory of Australia and informally as the Territory) is an states and territories of Australia, Australian internal territory in the central and central-northern regi ...
. Large amounts of fragmentary material found at the Alcoota fossil site in
Central Australia Central Australia, also sometimes referred to as the Red Centre, is an inexactly defined region associated with the geographic centre of Australia. In its narrowest sense it describes a region that is limited to the town of Alice Springs and ...
, the type location, are the only certain occurrence of the bird. Rich proposed the specific epithet for fellow
palaeontologist Paleontology, also spelled as palaeontology or palæontology, is the scientific study of the life of the past, mainly but not exclusively through the study of fossils. Paleontologists use fossils as a means to classify organisms, measure geolo ...
Ruben A. Stirton, an American who undertook extensive research on Australian taxa.


Description

''Dromornis stirtoni'' was a large feathered bird which grew up over in height. This height is thought to have exceeded the tallest species of the genus ''Dinornis'', which were the giant
moa Moa are extinct giant flightless birds native to New Zealand. Moa or MOA may also refer to: Arts and media * Metal Open Air, a Brazilian heavy metal festival * MOA Museum of Art in Japan * The Moas, New Zealand film awards People * Moa ...
s of
New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...
, and the Elephant Birds of Madagascar. This species is from the
Dromornithidae Dromornithidae, known as mihirungs (after Tjapwuring ''Mihirung paringmal'', "giant bird") and informally as thunder birds or demon ducks, were a clade of large, flightless Australian birds of the Oligocene through Pleistocene epochs. All are no ...
family, which is a family of large flightless birds endemic to Australia. The weight of the animal is also thought to have been exceedingly large. Peter F. Murray and Patricia Vickers-Rich, in their work "Magnificent Mihirungs" (2004), utilised three varying scientific methods to derive the approximate weight and size of the ''D. stirtoni''. This thorough analysis of the bones of ''D. stirtoni'' revealed that there was considerable
sexual dimorphism Sexual dimorphism is the condition where sexes of the same species exhibit different Morphology (biology), morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecy, di ...
, and that a fully grown male could weigh between , whilst a female would likely weigh between .Chinsamy, A., Handley, W. D., Yates. A. M., Worthy, T. H. (2016). Sexual dimorphism in the late Miocene mihirung Dromornis stirtoni (Aves: Dromornithidae) from the Alcoota Local Fauna of central Australia. Journal of Vertebrate Paleontology, 36:5, DOI: 10.1080/02724634.2016.1180298 The disparity in robustness was interpreted by the researchers as evidence of the biology of the species, behaviours such as incubation by the female, pair bonding, parental care and aggression while nesting, and courtship or display habits exhibited by extant waterfowl, the
anseriform Anseriformes is an order of birds also known as waterfowl that comprises about 180 living species of birds in three families: Anhimidae (three species of screamers), Anseranatidae (the magpie goose), and Anatidae, the largest family, which inc ...
s. In comparison to other known ratite elephant birds of the Aepyornithidae family, this made ''D. stirtoni'' the heaviest of all known discoveries. ''D. stirtoni'' was compared to ''
Aepyornis maximus ''Aepyornis'' is an extinct genus of elephant bird formerly Endemism, endemic to Madagascar. The genus had two species, the smaller ''A. hildebrandti'' and the larger ''A. maximus'', which is possibly the largest bird ever to have lived. Its clo ...
'' by the authors, the largest of that family. ''D. stirtoni'' was characterised by a deep lower jaw and a quadrate bone (which connects the upper and lower jaws) that was distinctly shaped. This narrow, deep bill, made up approximately two thirds of the skull. The front of this powerful jaw was used to cut, whilst the back of the jaw was used for crushing.Monroe, M. (2009). Dromornithidae. Retrieved from Australia Through Time:https://austhrutime.com/dromornithidae.htm Comparison of two partial crania with the near complete cranium of ''Dromornis planei'' (''Bullockornis'') shows the head of this species to be about 25% larger . Reconstruction of overlapping remains of the rostrum have revealed its form and size, the lower mandible would have been around 0.5 metres. The size and proportions of the head and its bill are comparable to that of mammals such as camels or horses The large bird had "stubby", reduced wings, which ultimately deemed it flightless. However, whilst the bird was flightless, a strong development between the bony crests and tuberosities, where the wings were attached, allowed them to flap their wings. The bird was also characterised by its large hind legs, which after the completion of biomechanical studies are confirmed to have been muscular, rather than slender, due to the size of the muscle attachments along the leg. Due to the muscularity of these legs, ''D. stirtoni'' is thought to have possibly been capable of running at great speeds, whereas birds such as the emu depend on the slenderness of their legs to reach higher speeds. ''D. stirtoni'' was also characterised by its large, hoof-like toes, which had convex nails, rather than claws. Further typical of flightless birds, it did not have a breastbone. Two forms of unearthed specimens are considered to be due to strong sexual dimorphism, concluded in a 2016
morphometric Morphometrics (from Greek μορΦή ''morphe'', "shape, form", and -μετρία ''metria'', "measurement") or morphometry refers to the quantitative analysis of ''form'', a concept that encompasses size and shape. Morphometric analyses are co ...
analysis using landmark based and actual measurements which also supported earlier conclusions regarding the species enormous size.Puiu, T. (2021). Giant Australian flightless bird was "extreme evolutionary experiment". Retrieved from ZME Science: https://www.zmescience.com/ecology/animals-ecology/giant-australian-flightless-bird-24032021/ This histological technique has been applied to other large and extinct avian species, including investigation into the paleobiology of the elephant birds Aepyornithidae. Osteohistological analysis of its femora, tibiotarsi, and tarsometatarsi has also revealed that ''D. stirtoni'' was extremely K-selected, likely requiring over a decade to reach its adult body size, after which skeletal maturity occurred and its growth rate retarded.


Habitat

At present the only recorded fossil discoveries of ''Dromornis stirtoni'' have been from the Alcoota Fossil Beds. This region is renowned for the discovery of well-preserved vertebrate fossils from the
Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...
epoch (24–5 million years ago). At this location, the fossil deposits are found in the Waite Formation, which consists of sandstones, limestones and siltstones. The various fossils that have been found within this region suggest that they were laid in episodical channels, characterised by a large series of interconnected lakes, within a large basin. The vegetation type of the region in that period was open woodland favouring its semi-arid climate, within which seasonal rainfall occurs. ''D. stirtoni'' is found amongst the depositions of the Alcoota and Ongeva Local Faunas, dated to the Late
Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...
and early
Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58dromornithid Dromornithidae, known as mihirungs (after Tjapwuring ''Mihirung paringmal'', "giant bird") and informally as thunder birds or demon ducks, were a clade of large, flightless Australian birds of the Oligocene through Pleistocene epochs. All are no ...
species have been found alongside this species, '' Ilbandornis woodburnei'' and the tentatively placed '' Ilbandornis lawsoni'', resembling the large but more gracile modern birds such as
ostriches Ostriches are large flightless birds. Two living species are recognised, the common ostrich, native to large parts of sub-Saharan Africa, and the Somali ostrich, native to the Horn of Africa. They are the heaviest and largest living birds, w ...
and
emu The emu (; ''Dromaius novaehollandiae'') is a species of flightless bird endemism, endemic to Australia, where it is the Tallest extant birds, tallest native bird. It is the only extant taxon, extant member of the genus ''Dromaius'' and the ...
s. The concentration of dromornithid species, and more generally, other fossils within this area is indicative of the phenomenon known as "waterhole-tethering", whereby animals would accumulate within the immediate area of water sources, many of which would then die. Whilst this is the only location that ''D. stirtoni'' have been discovered, discovery of other species within the Dromornithidae family suggests that they may have been distributed across Australia. Various Dromornithidae fossils have been found in Riversleigh (
Queensland Queensland ( , commonly abbreviated as Qld) is a States and territories of Australia, state in northeastern Australia, and is the second-largest and third-most populous state in Australia. It is bordered by the Northern Territory, South Austr ...
) and Bullocks Creek (
Northern Territory The Northern Territory (abbreviated as NT; known formally as the Northern Territory of Australia and informally as the Territory) is an states and territories of Australia, Australian internal territory in the central and central-northern regi ...
), as well as tracks in
Pioneer Pioneer commonly refers to a person who is among the first at something that is new to a community. A pioneer as a settler is among the first settling at a place that is new to the settler community. A historic example are American pioneers, perso ...
(
Tasmania Tasmania (; palawa kani: ''Lutruwita'') is an island States and territories of Australia, state of Australia. It is located to the south of the Mainland Australia, Australian mainland, and is separated from it by the Bass Strait. The sta ...
). ''D. stirtoni'' probably existed in an assemblage of fauna that included other dromornithids and browsing marsupials as the apex herbivores. The Alcoota Local Fauna were deposited at the only known upper Miocene fossil beds of Central Australia. The early conceptions of a fearsome bird receives some support from the proposed behaviour of the larger males aggressively defending a preferred range against competitors, other males or herbivores, and predators.


Feeding and diet

It is widely accepted that ''Dromornis stirtoni'' was herbivorous. This has been deduced from various features of its anatomy. One of these features is that the end of the bird's bill, does not have a hook, and that the beak is instead wide, narrow and blunt, typical of a herbivore. The bird also had hoof-like feet, rather than 'talons', which are typically associated with carnivores or omnivores. Lastly, analysis of the amino acids within the egg shells of ''D. stirtoni'' suggest that the species was herbivorous. Despite this however, there are various indicators that suggest the bird may have been carnivorous or omnivorous (Murray, 2004). The size and muscularity of the birds skull and beak would also suggest that they may not have been herbivores, as no source of vegetable food in their environment would have required such a powerful beak (Vickers-Rich, 1979). In recognition of the varying opinions, it is widely accepted that whilst the large bird may have occasionally scavenged or eaten smaller prey, they were mostly herbivorous.


Extinction

It is proposed that various factors may have contributed to the extinction of ''Dromornis stirtoni''. Palaeontologists Murray and Vickers-Rich suggested that the diet may have overlapped considerably with the diets of other large birds and animals, and that the subsequent converging trophic morphology could have contributed to the large birds extinction as it was 'out-competed' of its food source. Alternative arguments have proposed that the large birds' breeding patterns may have contributed. It's suggested that ''D. stirtoni'' lived for a relatively long period of time in a group of older birds; however, for the few young that were produced, time to maturity was considerable. Subsequently, breeding adults were replaced slowly, which left the species highly vulnerable if breeding adults were lost.


References


Further reading

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External links


Exhibit of reconstructed skeleton
{{Taxonbar, from=Q2048635, from2=Q909965, from3=Q23680568, from4=Q909973, from5=Q136317, from6=Q106704224 Extinct flightless birds Neogene birds of Australia Prehistoric bird genera Miocene birds Pliocene birds Fossil taxa described in 1872 Taxa named by Richard Owen