Brontornis
Encyclopedia
Brontornis was a genus
of giant flightless predatory bird
s that lived in Patagonia
. The only species currently accepted as valid is B. burmeisteri. It has traditionally been placed in the family Phorusrhacidae
, nicknamed "Terror Birds" for their large size and predatory lifestyle, and more precisely to the subfamily Brontornithinae, which contained extremely large and very heavyset forms.
It is known from bones, mainly of the legs and feet but also some skull and backbone parts, found in several localities of Santa Cruz Province
.
B. burmeisteri was the second largest species of phorusrhacid, with a height of around 2.80 meters (9.19 feet) and an estimated weight of 350–400 kg (Alvarenga & Höfling, 2003), making it the third-heaviest bird ever according to current knowledge (after Aepyornis maximus
and Dromornis stirtoni), and the most massive land predator of its time and place. Due to its bulk, it probably had a lifestyle between an ambush predator and one that actively chased prey, pouncing on the latter from a hideout and bringing it down by sheer force of attack after a short chase. In attacking prey (but probably not necessarily in a defensive situation, as it was too slow-moving) it most likely was the dominant carnivore
of Miocene
Patagonia, being able to kill even large animals such as the elephant-like Astrapotherium and in the predatory role being on par with a pack of Thylacosmilus
(metatheria
n sabre-tooth). It coexisted with some slightly smaller and more active phorusrhacids like Phorusrhacos
, but apparently became extinct before the appearance of the immense Argentavis
, the largest flying bird ever.
Possibly, the fossils described as B. platyonyx represent another species; they are about one-third smaller than the largest Brontornis bones. It is much more likely, however, that they represent sexual dimorphism
. In today's hawk
s and owl
s, females are usually considerably larger than the males; this prevents overutilization of one size class of prey. It is not known whether phorusrhacid males or females would have been larger, but the fossils of the North America
n phorusrhacid Titanis
also show considerable variation in size, suggesting that there was indeed at least a tendency for differently-sized sexes.
Some recent work has cast doubt on the hypothesis that Brontornis is a phorusrhacid; according to this research, it seems to actually be an anseriform
. The other genera traditionally assigned to the subfamily Brontornithinae (Physornis
and Paraphysornis
) apparently are true phorusrhacids so the subfamily containing them had been proposed to be renamed Physornithinae, with Physornis fortis as the type. If valid, this would mean that there are three groups of giant basal anseriformes, in chronological order of divergence first the gastornids
(relatives of Gastornis
) then Brontornis and finally the mihirungs
of Australia.
However, a subsequent analysis interprets Brontornis as having adaptations to great weight but exhibiting diagnostic thoracic vertebrae
, putting it back squarely within the phorusrhacids.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of giant flightless predatory bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
s that lived in Patagonia
Patagonia
Patagonia is a region located in Argentina and Chile, integrating the southernmost section of the Andes mountains to the southwest towards the Pacific ocean and from the east of the cordillera to the valleys it follows south through Colorado River towards Carmen de Patagones in the Atlantic Ocean...
. The only species currently accepted as valid is B. burmeisteri. It has traditionally been placed in the family Phorusrhacidae
Phorusrhacidae
Phorusrhacids , colloquially known as "terror birds" as the larger species were apex predators during the Miocene, were a clade of large carnivorous flightless birds that were the dominant predators in South America during the Cenozoic, 62–2 million years ago. They were roughly 1–3 meters tall...
, nicknamed "Terror Birds" for their large size and predatory lifestyle, and more precisely to the subfamily Brontornithinae, which contained extremely large and very heavyset forms.
It is known from bones, mainly of the legs and feet but also some skull and backbone parts, found in several localities of Santa Cruz Province
Santa Cruz Province (Argentina)
Santa Cruz is a province of Argentina, located in the southern part of the country, in Patagonia. It borders Chubut province to the north, and Chile to the west and south. To the east is the Atlantic Ocean...
.
B. burmeisteri was the second largest species of phorusrhacid, with a height of around 2.80 meters (9.19 feet) and an estimated weight of 350–400 kg (Alvarenga & Höfling, 2003), making it the third-heaviest bird ever according to current knowledge (after Aepyornis maximus
Aepyornis
Aepyornis is a genus of aepyornithid, one of two genera of ratite birds endemic to Madagascar known as elephant birds. This animal was the world's largest bird until its extinction, about 1000 years ago.-Description:...
and Dromornis stirtoni), and the most massive land predator of its time and place. Due to its bulk, it probably had a lifestyle between an ambush predator and one that actively chased prey, pouncing on the latter from a hideout and bringing it down by sheer force of attack after a short chase. In attacking prey (but probably not necessarily in a defensive situation, as it was too slow-moving) it most likely was the dominant carnivore
Carnivore
A carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging...
of Miocene
Miocene
The 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...
Patagonia, being able to kill even large animals such as the elephant-like Astrapotherium and in the predatory role being on par with a pack of Thylacosmilus
Thylacosmilus
Thylacosmilus was a genus of sabre-toothed metatherian predators that first appeared during the Miocene. Remains of the animal have been found in parts of South America, primarily Argentina...
(metatheria
Metatheria
Metatheria is a grouping within the animal class Mammalia. First proposed by Thomas Henry Huxley in 1880, it is nearly synonymous with the earlier taxon Marsupialia though it is slightly wider since it also contains the nearest fossil relatives of marsupial mammals.The earliest known...
n sabre-tooth). It coexisted with some slightly smaller and more active phorusrhacids like Phorusrhacos
Phorusrhacos
Phorusrhacos was a genus of giant flightless predatory birds that lived in Patagonia, containing the single species Phorusrhacos longissimus. Their closest living relatives are the much smaller seriema birds...
, but apparently became extinct before the appearance of the immense Argentavis
Argentavis
Argentavis magnificens is the largest flying bird ever discovered. This bird, sometimes called the Giant Teratorn, is an extinct species known from three sites from the late Miocene of central and northwestern Argentina, where a good sample of fossils has been obtained.The humerus of...
, the largest flying bird ever.
Classification
There are several synonyms of the species and genus:- Rostrornis floweri MorenoFrancisco MorenoFrancisco Pascacio Moreno was a prominent explorer and academic in Argentina, where he is usually referred to as Perito Moreno...
& Mercerat, 1891 - Brontornis platyonyx AmeghinoFlorentino AmeghinoFlorentino Ameghino was an Argentine naturalist, paleontologist, anthropologist and zoologist.Born in Luján, son of Italian immigrants, Ameghino was a self-taught naturalist, and focused his study on the lands of the southern Pampas...
, 1895
Possibly, the fossils described as B. platyonyx represent another species; they are about one-third smaller than the largest Brontornis bones. It is much more likely, however, that they represent sexual dimorphism
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
. In today's hawk
Hawk
The term hawk can be used in several ways:* In strict usage in Australia and Africa, to mean any of the species in the subfamily Accipitrinae, which comprises the genera Accipiter, Micronisus, Melierax, Urotriorchis and Megatriorchis. The large and widespread Accipiter genus includes goshawks,...
s and owl
Owl
Owls are a group of birds that belong to the order Strigiformes, constituting 200 bird of prey species. Most are solitary and nocturnal, with some exceptions . Owls hunt mostly small mammals, insects, and other birds, although a few species specialize in hunting fish...
s, females are usually considerably larger than the males; this prevents overutilization of one size class of prey. It is not known whether phorusrhacid males or females would have been larger, but the fossils of the North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
n phorusrhacid Titanis
Titanis
Titanis is a large extinct flightless carnivorous bird of the family Phorusrhacidae, endemic to North America during the Blancan stage of the Pliocene living 4.9—1.8 Ma, and died out during the Gelasian Age of the earliest Pleistocene, existing approximately .-Etymology:The generic name, Titanis,...
also show considerable variation in size, suggesting that there was indeed at least a tendency for differently-sized sexes.
Some recent work has cast doubt on the hypothesis that Brontornis is a phorusrhacid; according to this research, it seems to actually be an anseriform
Anseriformes
The order Anseriformes contains about 150 living species of birds in three extant families: the Anhimidae , Anseranatidae , and the Anatidae, which includes over 140 species of waterfowl, among them the ducks, geese, and swans.All species in the order are highly adapted for an aquatic existence at...
. The other genera traditionally assigned to the subfamily Brontornithinae (Physornis
Physornis
Physornis is an extinct genus of giant flightless predatory birds of the family Phorusrhacidae or "terror birds" that lived in Argentina. The only known species is Physornis fortis. It lived from 28 to 23 million years ago....
and Paraphysornis
Paraphysornis
Paraphysornis is an extinct genus of giant flightless predatory birds of the family Phorusrhacidae or "terror birds" and the subfamily brontornithinae that lived in Brazil. Its length was about 2 meter and the skull had a length of 60 centimeter. The only known species is Paraphysornis...
) apparently are true phorusrhacids so the subfamily containing them had been proposed to be renamed Physornithinae, with Physornis fortis as the type. If valid, this would mean that there are three groups of giant basal anseriformes, in chronological order of divergence first the gastornids
Gastornithiformes
Gastornithiformes are an order of prehistoric birds. The birds from this group lived from the Paleocene to the Eocene and were spread out across Asia, Europe, and North America. All the birds were very large birds that were flightless, similar to an ostrich but more heavily built and with a huge...
(relatives of Gastornis
Gastornis
Gastornis is an extinct genus of large flightless bird that lived during the late Paleocene and Eocene epochs of the Cenozoic. It was named in 1855, after Gaston Planté, who had discovered the first fossils in Argile Plastique formation deposits at Meudon near Paris...
) then Brontornis and finally the mihirungs
Dromornithidae
Dromornithidae — the dromornithids — were a family of large, flightless Australian birds of the Oligocene through Pleistocene epochs. All are now extinct. They were long classified in the order Struthioniformes, but are now usually classified as a family of Anseriformes1...
of Australia.
However, a subsequent analysis interprets Brontornis as having adaptations to great weight but exhibiting diagnostic thoracic vertebrae
Thoracic vertebrae
In human anatomy, twelve thoracic vertebrae compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. They are intermediate in size between those of the cervical and lumbar regions; they increase in size as one proceeds down the spine, the upper...
, putting it back squarely within the phorusrhacids.