Brontornis

Taxobox
name = "Brontornis"


image_caption = "B. murmeisteri" reconstructed as a phorusrhacid
fossil_range = Early - Middle Miocene
regnum = Animalia
phylum = Chordata
classis = Aves
ordo = Gruiformes
familia = Phorusrhacidae
genus = "Brontornis"
genus_authority = Moreno & Mercerat, 1891
species = "B. burmeisteri"
binomial = "Brontornis burmeisteri"
binomial_authority = Moreno & Mercerat, 1891
synonyms ="see text"

"Brontornis" was a genus of giant flightless predatory birds that lived in Patagonia. The only species currently accepted as valid is "B. burmeisteri". It belonges to 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 largest species of phorusrhacid, with a height of around 2.80 meters 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" (marsupialian 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.

ynonyms

There are several synonyms of the species and genus:

Genus-level synonym:
* "Rostrornis" Moreno & Mercerat, 1891

Species-level synonymy:
* "Rostrornis floweri" Moreno & Mercerat, 1891
* "Brontornis platyonyx" Ameghino, 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. In today's hawks and owls, 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 American phorusrhacid "Titanis" also show considerable variation in size, suggesting that there was indeed at least a tendency for differently-sized sexes.

References

* Alvarenga, Herculano M. F. & Höfling, Elizabeth (2003): "Systematic revision of the Phorusrhacidae (Aves: Ralliformes)". "Papéis Avulsos de Zoologia" 43(4): 55-91 [http://www.scielo.br/scielo.php?script=sci_pdf&pid=S0031-10492003000400001&lng=en&nrm=iso&tlng=en PDF fulltext]
* Moreno, Francisco P. & Mercerat, A. (1891): Catálogo de los pájaros fósiles de la República Argentina conservados en el Museo de La Plata. "Anales del Museo de La Plata" 1: 7-71.
*Agnolin, F. 2007. Brontornis burmeisteri Moreno & Mercerat, un Anseriformes (Aves) gigante del Mioceno Medio de Patagonia, Argentina. Revista del Museo Argentino de Ciencias Naturales, n.s. 9, 15-25http://dml.cmnh.org/2000Mar/msg00218.htmlhttp://dml.cmnh.org/2000Mar/msg00099.htmlhttp://darrennaish.blogspot.com/2006/11/more-on-phorusrhacids-biggest-fastest.htmlhttp://scienceblogs.com/tetrapodzoology/2008/06/2007_year_of_terror_birds.php