Brontornis

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Brontornis
Temporal range: Early-Mid Miocene (Santacrucian-Laventan)
~17.5–11.6  Ma
Brontornis burmeisteri femore sinistro.JPG
Fossil femur
Brontornis burmeisteri tarsometatarso sinistro.JPG
Fossil tarsometatarsus
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Infraclass: Neognathae
Genus:† Brontornis
Moreno & Mercerat 1891
Type species
†Brontornis burmeisteri
Moreno & Mercerat 1891
Synonyms
Genus synonymy
  • RostrornisMoreno & Mercerat 1891
  • LiornisMoreno & Mercerat 1891 (in part)
Species synonymy
  • Rostrornis floweri Moreno & Mercerat 1891
  • Brontornis platyonyxAmeghino 1895
  • Liornis floweri Ameghino 1895

Brontornis is an extinct genus of giant bird that inhabited Argentina during the Early to Middle Miocene. [1] Its taxonomic position is highly controversial, with authors alternatively considering it to be a cariamiform, typically a phorusrhacid (terror bird) or an anserimorph.

Contents

Taxonomy

The first fossils of Brontornis burmeisteri were described by paleontologists Francisco Moreno and Alcides Mercerart in 1891, the fossils being a left femur, tibiotarsus, fibula, and tarsometatarsus all from the same individual found in the Lower-Middle Miocene strata of the Santa Cruz Formation in Santa Cruz Province, Argentina. [2] [3] In the same paper, two distal tibiotarsi from the same area were referred to Brontornis as well. [3] [4] Unknowingly, Moreno & Mercerat also named a species now seen as synonymous with Brontornis burmeisteri, Rostrornis floweri, that includes: various bill and skull fragments, seven vertebrae and fragments, femoral head, lower part of left femur, ectocondyle of right tibiotarsus. [4] [3] Some pedal phalanges and a trochleae of tarsometatarsus were also referred to the type, but they haven't been described in detail. [3] These fossils were found in the lower Miocene Monte León Formation, one of the two formations the taxon is definitively known from. [3] [2] Some additional fossils, including a quadrate, were referred to Brontornis by Moreno & Mercerart in 1891, but these were dubiously referred. Mercerat named another taxon synonymized with Brontornis, Stephanornis princeps, in 1893, though the fossil is now lost so this assessment is unverifiable. [3]

Moreno's rival, Florentino Ameghino, also found fossils of Brontornis which he named Brontornis platyonyx in 1895 based on four pedal phalanges found at Monte Leon. [2] [3] The species has been synonymized with Brontornis. Ameghino also named Liornis floweri based on a distal tibiotarsus, distal tarsometatarsus, and two pedal phalanges of a juvenile that was synonymized with Brontornis in 1967. [5] [3] Liornis minor was also synonymized in 1967, but it has since been synonymized with Phorusrhacos. [3] [5] Callornis giganteus, another Ameghino taxon, may also be a synonym of Brontornis or a distinct close relative. [5] Recently, the affinities of some Brontornis specimens has come into question due to the uncertain and debated phylogenetic position of the genus and its synonyms. [2]

Evolution

Speculative life restoration of Brontornis as an anserimorph Brontornis burmeisteri life reconstruction.jpg
Speculative life restoration of Brontornis as an anserimorph

Recent work has cast doubt on the hypothesis that Brontornis is a phorusrhacid. Brontornis may actually represent an anseriform, with other genera traditionally assigned to Brontornithinae ( Physornis and Paraphysornis ) being true phorusrhacids. The subfamily containing the latter two had been proposed to be renamed to Physornithinae, with Physornis fortis as the type species. If these conclusions are valid, this would mean that there are three groups of giant basal anseriformes, in chronological order of divergence: the gastornithids ( Gastornis and kin), Brontornis, and finally the mihirungs of Australia. [6] However, other analyses have also argued that Brontornis exhibits thoracic vertebrae diagnostic of phorusrhacids, supporting its placement within that group. [6]

Brontornis is a genus of birds (Aves), which is sometimes referred to its own family Brontornithidae. These are very large, flightless birds from the Miocene of South America and are known from very fragmentary material. The exact systematic assignment of Brontornis and the Brontornithidae is very uncertain and in a constant flux, which is largely due to the fragmentary nature of the remains. Originally placed on the base of the Phorusrhacidae ("terror birds"), [1] [4] there are several different views on its classification today. After several cladistic studies, the Brontornithidae have been found as basal geese relatives. [7] [6] On the other hand, they also form the sister group of the Cariamiformes, which combine today's Seriema and the Phorusrhacidae. [8] Since the introduction of the Brontornithidae as a family group, this has mostly been considered monogeneric or monospecific. [3] Some authors have considered other genera as possible relatives, but most of these have been regarded as synonyms of Brontornis [3] or Phorusrhacos. [1] However, a Tibiotarsus of a large bird similar to Brontornis was found in Oligocene strata in Salla-Luribay, Bolivia, making it the oldest known Brontornithid fossil known. [9]

Traditionally, Brontornis was usually attributed as a genus to the extinct family of the Phorusrhacidae ("Terror birds"), [1] [3] which was quite widespread in South America and comprises large to very large, mostly predatory birds. These are related to the seriama, sharing features such as a hook-shaped upper beak and the curved ungues, which had sharp claws and thus distinguish the birds as predatory carnivores. Within the Phorusrhacids, Brontornis was referred to their own subfamily of Brontornithinae, very large and massive birds which also included physical territories and paraphysis. The allocation to the Phorusrhacidae was mainly based of the strong lower jaw symphysis and the targeted Tarsometatatarsus at the front and back, and was supported by Herculano M. F. Alvarenga and Elizabeth Höfling in 2003. [1] A revision of the genre of Federico L. Agnolin in 2007 rejects the assignment based on these characteristics to the Phorusrhacids, since they also occur in other early large running birds, for example in Anserimorphs or within the Dromornithidae. [6] The rotation of the middle shape of the Tibiotarsus and the construction of the square leg suggest for a closer relationship with the goose family (aneriform) rather than Phorusrhacidae. [6] [2] For these reasons, Brontornis was excluded from the Phorusrhacids and moved to the base of the goose birds by Agnolin. [6] [2] Physornis and Paraphysornis , on the other hand, have been considered close relatives of Brontornis in their own subfamily in Phorusrhacidae, Brontornithinae, [10] [1] though it is sometimes referred to as Physornithinae. [11] [12] [6]

This phylogenetic position for Brontornis had originally been favored by the first descriptions of the genus, but Mathilde Dolgopol de Sáez classified it as a relative of geese and Gastornis in 1927. [13] Subsequently, after Agnolin's revision, his analysis was met with some approval from other paleontologists, but disagreements from other. [14] [15]

A phylogenetic analysis of Phorusrhacidae in 2011 again concluded that Brontornis was justified in the placement with the special expression of a fragmented thoracic vertebrae. [16] Once again, suggesting that Brontornis sat within Anserimorpha. [11]

With other cladist analyses suggested the structure of resemble that of Anserimorphs. [17] The lack of the striking bone footbridge (Pons Supratendineus) on the front of the lower joint of the tibiotarsus of Brontornis was also pointed out several times, which in occurs in the Phorusrhacidae. [5] [18] Furthermore, the short and robust construction of the mandible contrasts to the long and slim mandibles of Phorusrhacids, again suggested that Brontornis isn't a phorusrhacid. According to the examinations already mentioned, the different design of the lower jaw also results in a different diet of Brontornis than Phorusrhacids. [18] [13]

However, a study from 2017 suggested that Brontornis belonged to sister taxon to Cariamiformes. As a result, the genus moved close to the Phorusrhacidae, but not directly in it. [19] Suggesting that the previous study a misinterpreted the orientation of the tarsometatarsus as a central point of systematic assignment of Brontornis. It was pointed out that, the previous studies only used sparse material of Brontornis. However, a 2021 study once again found Brontornis to be a Gastornithiform. [2]

Description

Size

Size comparison of Brontornis (red), Kelenken (yellow) and a human Brontornis vs Kelenken.jpg
Size comparison of Brontornis (red), Kelenken (yellow) and a human

Due to the size of the finds, a height of 280 centimetres (9.2 ft) is assumed. The pronounced massiveness of the bones leads to weight estimates between 350 and 400 kilograms (770 and 880 lb) [1] or 319 to 350 kilograms (703 to 772 lb), [17] [13] however, some finds have clear size differences that can reach up to 33% based on the tarsometatarsus. A comparison of the tarsometatarsi of two B. burmeisteri specimens, FM-P13259 and MLP-91 (lectotype), both coming from the same geographical region and geological formation, shows them as not to present any anatomical differences, apart from size, where in the first is around one third smaller than the second. The idea is that they are examples of intraspecific variation, possibly sexual dimorphism. There is the possibility that they represent two species. [20] These measures would make Brontornis the fourth-heaviest bird found thus far, after Aepyornis maximus , Dromornis stirtoni , and Pachystruthio dmanisensis . [21]

Paleobiology

Diet

There is uncertainty about the species' diet, due to the lack of well preserved skull material and overlap between specimens. [17] Due to the original placement within the "terror birds" grouping, some researchers believe that Brontornis could have been a carrion eater. [1] Correspondingly, art and skull reconstructions depicted Brontornis with a sharp and hooked top beak, [1] though paleontologists are unsure because the tip of the preserved mandibles is missing. [13]

Contrarily, some paleontologists have proposed an herbivorous diet for Brontornis. [6] Studies on the lower jaw indicate that it was most likely not suitable for tearing animal food. The width and strong lower jaw is similar to that of Gastornis and Aepyornis, two herbivorous large birds. Likewise, the ungues of Brontornis do not show stronger bends compared to Phorusrhacids and thus do not allow raptor-like claws for tearing meat, which suggests a more plant-based diet. [18] [13] Considering its enormous body size, it is assumed that Brontornis inhabited more open landscapes, as they have also been proven for the Santa Cruz formation. [22] The short and wide Tarsometatarsus compared to the Tibiotarsus suggests a slow locomotion adapted to the enormous body mass. [16]

Related Research Articles

<span class="mw-page-title-main">Anseriformes</span> Order of water birds

Anseriformes is an order of birds also known as waterfowl that comprises about 180 living species of birds in three families: Anhimidae, Anseranatidae, and Anatidae, the largest family, which includes over 170 species of waterfowl, among them the ducks, geese, and swans. Most modern species in the order are highly adapted for an aquatic existence at the water surface. With the exception of screamers, males have penises, a trait that has been lost in the Neoaves. Due to their aquatic nature, most species are web-footed.

<span class="mw-page-title-main">Phorusrhacidae</span> Extinct family of flightless 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 the Middle Eocene to the Late Pleistocene around 43 to 0.1 million years ago, though some specimens suggest that they were present since the Early Eocene.

<i>Phorusrhacos</i> Extinct genus of birds

Phorusrhacos is an extinct genus of giant flightless terror birds that inhabited South America during the Miocene epoch. Phorusrhacos was one of the dominant land predators in South America at the time it existed. It is thought to have lived in woodlands and grasslands.

<i>Titanis</i> Extinct genus of birds

Titanis is a genus of phorusrhacid, an extinct family of large, predatory birds, in the order Cariamiformes that inhabited the United States during the Pliocene and earliest Pleistocene. The first fossils were unearthed by amateur archaeologists Benjamin Waller and Robert Allen from the Santa Fe River in Florida and were named Titanis walleri by ornithologist Pierce Brodkorb in 1963, the species name honoring Waller. The holotype material is fragmentary, consisting of only an incomplete right tarsometatarsus and phalanx, but comes from one of the largest phorusrhacid individuals known. In the years following the description, many more isolated elements have been unearthed from sites from other areas of Florida, Texas, and California. The species was classified in the subfamily Phorusrhacinae, which includes some of the last and largest phorusrhacids like Devincenzia and Kelenken.

<i>Andalgalornis</i> Extinct genus of birds

Andalgalornis is a genus of flightless predatory birds of the extinct family Phorusrhacidae that lived in Argentina. The type and only species is A. steulleti.

<i>Strigogyps</i> Extinct genus of birds in the familie Ameghinornithidae

Strigogyps is an extinct genus of prehistoric bird from the Middle Eocene to Early Oligocene of France and Germany. It was probably around the size of a large chicken or a guan, weighing not quite 1 kilogram (2.2 lb). Apparently, as indicated by the ratio of lengths of wing to leg bones, S. sapea was flightless. Its legs were not adapted to running, so it seems to have had a walking lifestyle similar to trumpeters. Unlike other Cariamiformes which appear to have been mostly carnivorous, the specimens of one species, Strigogyps sapea, suggest a facultatively herbivorous or omnivorous diet.

<i>Mesembriornis</i> Extinct genus of birds

Mesembriornis is a genus of intermediate-sized phorusrhacids that grew up to 1.5 metres (4.9 ft) in height. They represent a well-distinct lineage of terror birds, differing from the massive large groups and the smaller Psilopterinae. In general proportions, they most resembled the Patagornithinae which flourished somewhat earlier, mainly to the south of the range of Mesembriornis. Fossils of the terror bird have been found in Montehermosan deposits of the Monte Hermoso Formation, as well as the Andalgala Formation and Chapadmalal Formation in Argentina.

<span class="mw-page-title-main">Gastornithiformes</span> Extinct order of birds

Gastornithiformes are an extinct order of giant flightless fowl with fossils found in North America, Eurasia, possibly Australia. Members of Gastornithidae were long considered to be a part of the order Gruiformes. However, the traditional concept of Gruiformes has since been shown to be polyphyletic.

<i>Paraphysornis</i> Extinct genus of birds

Paraphysornis is an extinct genus of giant flightless terror birds that inhabited Brazil during Late Oligocene or Early Miocene epochs. Although not the tallest phorusrhacid, Paraphysornis measured up to 1.4 metres tall at the hips and weighed around 180–240 kilograms (400–530 lb). It was also a notably robust bird, having short and robust tarsal bones not suited for pursuit hunting.

<i>Kelenken</i> Extinct genus of birds

Kelenken is a genus of phorusrhacid, an extinct group of large, predatory birds, which lived in what is now Argentina in the middle Miocene about 15 million years ago. The only known specimen was discovered by high school student Guillermo Aguirre-Zabala in Comallo, in the region of Patagonia, and was made the holotype of the new genus and species Kelenken guillermoi in 2007. The genus name references a spirit in Tehuelche mythology, and the specific name honors the discoverer. The holotype consists of one of the most complete skulls known of a large phorusrhacid, as well as a tarsometatarsus lower leg bone and a phalanx toe bone. The discovery of Kelenken clarified the anatomy of large phorusrhacids, as these were previously much less well known. The closest living relatives of the phorusrhacids are the seriemas. Kelenken was found to belong in the subfamily Phorusrhacinae, along with for example Devincenzia.

Physornis is an extinct genus of giant flightless predatory birds of the family Phorusrhacidae or "terror birds", most closely related to Paraphysornis, that lived in Argentina. The type species is P. fortis. It lived during the Middle to Late Oligocene (Deseadan). Few fossils are known, but the available material suggests that Physornis was one of the largest phorusrhacids.

<i>Devincenzia</i> Extinct genus of birds

Devincenzia is an extinct genus of giant flightless predatory birds in the family Phorusrhacidae or "terror birds" that lived during the Early Miocene (Deseadan) Fray Bentos Formation of Uruguay, Late Miocene (Huayquerian) Ituzaingó Formation, Early Pliocene (Montehermosan) of Argentina, and possibly the Early Pleistocene Raigón Formation of Uruguay. The type species D. pozzi was formerly known as Onactornis pozzi. The largest possible specimen weighed up to 350 kilograms (770 lb), making it one of the largest phorusrhacids and carnivorous birds known.

<i>Patagornis</i> Extinct genus of birds

Patagornis is a genus of extinct flightless predatory birds of the family Phorusrhacidae. Known as "terror birds", these lived in what is now Argentina during the Early and Middle Miocene; the Santa Cruz Formation in Patagonia contains numerous specimens. Patagornis was an agile, medium sized Patagornithine and was likely a pursuit predator.

<i>Andrewsornis</i> Extinct genus of birds

Andrewsornis is an extinct genus of giant flightless predatory birds of the family Phorusrhacidae or "terror birds" that lived in Oligocene Argentina. Fossils have been found in the Sarmiento Formation, and possibly the Agua de la Piedra Formation.

<i>Procariama</i> Extinct genus of birds

Procariama is an extinct monotypic genus of phorusrhacid, which lived from the Late Miocene to the Late Pliocene of Argentina. Fossils of the animal have been found in six places, in the Cerro Azul and Andalhuala Formations. More specifically in the Andagalá department and in the north of the Belén department of the Catamarca province, with a single location in the La Pampa province. The type and only species, Procariama simplex, is the largest member of the subfamily Psilopterinae.

<i>Psilopterus</i> Extinct genus of birds

Psilopterus is an extinct genus of phorusrhacid from the Middle Oligocene to possibly the Late Pleistocene of Argentina and Uruguay. Compared to other phorusrhacids, members of the genus are both relatively gracile and diminutive, and include the smallest known species of terror bird: with the head raised P. bachmanni was 70–80 centimeters (2.3–2.6 ft) in height and weighed about 5 kilograms (11 lb), while the largest members of the genus were only about 8 kilograms (18 lb). The birds resemble the modern cariama, except with a heavier build and considerably smaller wings. Fossil finds in Uruguay indicate the genus may have survived until 96,040 ± 6,300 years ago, millions of years after the larger phorusrhacids became extinct.

<i>Eleutherornis</i> Extinct genus of birds

Eleutherornis cotei is an extinct flightless predatory cariamiform bird which lived during the Middle Eocene of France and Switzerland. Since the early 20th century, researchers have initially described the fossils of Eleutherornis as separate taxa, some remains as a species of Gastornis and others as an ancient ratite related to modern ostriches. However, subsequent analyses have questioned the original interpretations, and a thorough reexamination in 2013 indicated that all of these described remains represent the same species.

<span class="mw-page-title-main">Odontoanserae</span> Clade of birds

The Odontoanserae is a proposed clade that includes the family Pelagornithidae and the clade Anserimorphae. The placement of the pseudo-toothed birds in the evolutionary tree of birds has been problematic, with some supporting the placement of them near the orders Procellariformes and Pelecaniformes based on features in the sternum.

Dryornis, also called the Argentinian vulture, is an extinct genus of cathartid, known from Argentina. The genus contains two species, D. pampeanus and D. hatcheri.

References

  1. 1 2 3 4 5 6 7 8 9 Alvarenga, H. M., & Höfling, E. (2003). Systematic revision of the Phorusrhacidae (Aves: Ralliformes). Papéis Avulsos de Zoologia, 43(4), 55-91.
  2. 1 2 3 4 5 6 7 Agnolin, Federico L. (2021). "Reappraisal on the Phylogenetic Relationships of the Enigmatic Flightless Bird (Brontornis burmeisteri) Moreno and Mercerat, 1891". Diversity. 13 (2): 90. doi: 10.3390/d13020090 . ISSN   1424-2818.
  3. 1 2 3 4 5 6 7 8 9 10 11 12 Brodkorb, P. (1967). Catalogue of fossil birds: part 3 (Ralliformes, Ichthyornithiformes, Charadriiformes). University of Florida.
  4. 1 2 3 Moreno, F. P., & Mercerat, A. (1891). Catálogo de los pájaros fósiles de la República Argentina conservados en el Museo de La Plata. Taller de Publicaciones del Museo.
  5. 1 2 3 4 Buffetaut, E. (2016). A reassessment of the giant birds Liornis floweri Ameghino, 1895 and Callornis giganteus Ameghino, 1895, from the Santacrucian (late Early Miocene) of Argentina. Palaeovertebrata, 40, e3.
  6. 1 2 3 4 5 6 7 8 Agnolin, F. (2007). Brontornis burmeisteri Moreno & Mercerat, un Anseriformes (Aves) gigante del Mioceno Medio de Patagonia, Argentina. Revista del museo argentino de ciencias naturales nueva serie, 9(1), 15-25.
  7. ↑ Tambussi, C. P., & Degrange, F. J. (2013). Neogene Birds of South America. In South American and Antarctic Continental Cenozoic Birds (pp. 59-86). Springer, Dordrecht.
  8. ↑ Worthy, Trevor H.; Degrange, Federico J.; Handley, Warren D.; Lee, Michael S. Y. (2017). "The evolution of giant flightless birds and novel phylogenetic relationships for extinct fowl (Aves, Galloanseres)". Royal Society Open Science. 4 (10): 170975. Bibcode:2017RSOS....470975W. doi:10.1098/rsos.170975. PMC   5666277 . PMID   29134094.
  9. ↑ Buffetaut, E. (2017). A brontornithid from the Deseadan (Oligocene) of Bolivia. Contrib. Mus. Argent. Cienc. Nat, 7, 39-47.
  10. ↑ Acosta-Hospitalache, C., & Tambussi, C. (2005). Phorusrhacidae Psilopterinae (Aves) en la Formación Sarmiento de la localidad de Gran Hondonada (Eoceno Superior), Patagonia, Argentina. Spanish Journal of Palaeontology, 20(2), 127-132.
  11. 1 2 Silva, L. G. D. (2020). Revisão sobre a biomecânica da família Phorusrhacidae.
  12. ↑ Tambussi, C. P., & Degrange, F. J. (2013). The Paleogene birds of South America. In South American and Antarctic Continental Cenozoic Birds (pp. 29-47). Springer, Dordrecht.
  13. 1 2 3 4 5 Buffetaut, E. (2014). Tertiary ground birds from Patagonia (Argentina) in the Tournouër collection of the Muséum National d’Histoire Naturelle, Paris. Bulletin de la Société géologique de France, 185(3), 207-214.
  14. ↑ Tambussi, C. P. (2011). Palaeoenvironmental and faunal inferences based on the avian fossil record of Patagonia and Pampa: what works and what does not. Biological Journal of the Linnean Society, 103(2), 458-474.
  15. ↑ Lee, Michael S. Y. (20 October 2017). "Supplementary material from "The evolution of giant flightless birds and novel phylogenetic relationships for extinct fowl (Aves, Galloanseres)"". The Royal Society. doi:10.6084/m9.figshare.c.3897364.v2.
  16. 1 2 Angst, Delphine; Buffetaut, Eric; Lecuyer, Christophe; Amiot, Romain (2016). "Dryad Data -- A new method for estimating locomotion type in large ground birds". Dryad. doi:10.5061/dryad.609j4.
  17. 1 2 3 Degrange, F. J., Noriega, J. I., & Areta, J. I. (2012). Diversity and paleobiology of the Santacrucian birds. Early Miocene paleobiology in Patagonia: high-latitude paleocommunities of the Santa Cruz Formation, 138-155.
  18. 1 2 3 Buffetaut, E. THE BRONTORNITHIDAE: NEW DATA ABOUT AN OLD PALAEORNITHOLOGICAL RIDDLE.
  19. ↑ Worthy, Trevor H.; Degrange, Federico J.; Handley, Warren D.; Lee, Michael S. Y. (11 October 2017). "The evolution of giant flightless birds and novel phylogenetic relationships for extinct fowl (Aves, Galloanseres)". Royal Society Open Science. 4 (10): 170975. Bibcode:2017RSOS....470975W. doi:10.1098/rsos.170975. ISSN   2054-5703. PMC   5666277 . PMID   29134094.
  20. ↑ Alvarenga & Höfling, 2003
  21. ↑ Alvarenga & Höfling, 2003
  22. ↑ Tambussi, C. P., & Degrange, F. (2012). South American and Antarctic continental Cenozoic birds: Paleobiogeographic affinities and disparities. Springer Science & Business Media.
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