Brontornis
| Brontornis | ||||||||||||
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| Temporal occurrence | ||||||||||||
| Miocene | ||||||||||||
| 27 to 17 million years | ||||||||||||
| Locations | ||||||||||||
| Systematics | ||||||||||||
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| Scientific name of the family | ||||||||||||
| Brontornithidae | ||||||||||||
| Moreno & Mercerat, 1891 | ||||||||||||
| Scientific name of the genus | ||||||||||||
| Brontornis | ||||||||||||
| Moreno & Mercerat , 1891 | ||||||||||||
| Art | ||||||||||||
Brontornis is an extinct flightless species of bird from the family of Brontornithidae that in the Miocene in South America lived and is one of the largest known bird that lived on Earth. It has only been proven from a few dozen bone fragments, most of which come from the Santa Cruz Formation . Originally Brontornis was placed among the "terror birds" ( Phorusrhacidae ), but new investigations showed a more likely position close to the basis of the evolutionary evolution of the geese birds . It is not yet clear whether the representatives of Brontornis lived predatory or herbivorous life, but the structure of the lower jaw and the design of the claws on the toes advocate a preference for vegetable food.
features
The representatives of Brontornis had a heavy build, short legs, powerful beaks and strongly receded wings, but the genus is only known from a few finds. The square leg typical of birds differed somewhat from that of the Phorusrhacidae ("terror birds"), to which the genus was originally assigned, due to individual reduced bone protrusions and was more similar to the corresponding bone of the Dromornithidae . The beak is incomplete and has only survived through remains of the lower jaw, but these also reveal striking differences. The largest known fragment is 26.5 cm long and shows that the lower jaw had a much more massive and wider design. The body of the bone was up to 11 cm high, the symphysis , on the other hand, was low and very strongly compressed in front and behind. With a length of also 11 cm it looked comparatively short and still very wide with a length of 9.2 cm at the rear end. In its overall shape, the lower jaw is reminiscent of that of the geese , it was also significantly shorter, wider and more massive than that of the "terror birds". The leg bones were also very robust and large. The tarsometatarsus was around 40 cm long, but was relatively short and wide, the tibiotarsus almost doubled in length at 75 cm. Another difference to the "terror birds" is the development of the terminal phalanges of the feet. In Brontornis these were subtriangular in cross-section and in the side view not as strongly curved like birds of prey as in the Phorusrhacids. As a result, the claws of Brontornis roughly corresponded to those of Gastornis , a large ratite that is also extinct today.
Fossil finds
Brontornis has been proven to be fossilized only in the southern part of South America , where the find material was discovered in the Argentine province of Santa Cruz in Patagonia . This is 27 to 17 million years old, whereby it belongs to the Lower and Middle Miocene , some of the fossils can be assigned to the Santa Cruz Formation , which is to be placed in the transition from the Lower to the Middle Miocene. However, so far only a few dozen remains are known, some of which are also very fragmented, and parts of the lower jaw, especially the anterior symphysis , and the square bone , but also individual thoracic vertebrae and parts of the treads, especially the femur , the tibiotarsus , the tarsometatarsus and some Include phalanges . Significant sites are the Lago Argentino inland or Monte León and Monte Observación on the east coast of Argentina.
Paleobiology
height
Due to the size of the finds, a crown height of 280 cm is assumed. The pronounced massiveness of the bones leads to weight estimates between 350 and 400 kg and 319 to 350 kg. However, some finds show significant differences in size, which in the case of the tarsometatarsus can reach up to 33%. Due to the scarce evidence, it is unclear whether it is an intraspecific sexual dimorphism or a representative of two different species. Despite this, Brontornis was one of the largest and heaviest birds that ever lived on earth, with the stated values. Only Aepyornis maximus , which survived into the Young Holocene , achieved comparable dimensions with presumably more than 400 kg and roughly the same height, for Dromornis stirtoni , also from the Miocene, an estimated weight of up to 570 kg is assumed. The three species are in part very similar in their physique, but they were not closely related to one another and belong to different families.
Diet
Furthermore, there is a lack of clarity about the diet, since skull finds are rare and so far only very fragmented. Due to the originally assumed relationship with the "terror birds" and the short tarsometatarsus compared to the tibiotarsus , some researchers assume that Brontornis could have been a scavenger that was adapted to low running speeds. Correspondingly frequently depicted live reconstructions with a pointed, hook-shaped upper beak are uncertain, however, as there are no finds of this so far. Other scientists, however, suspect a more herbivorous way of life. Research on the lower jaw indicates that it was most likely unsuitable for mangling animal food. The broad and strong lower jaw resembles that of Gastornis and Dromornis , although today a more herbivorous diet is assumed for both, similar to what Aepyornis has been known for a long time. The end phalanges of Brontornis as well as those of Gastornis show no stronger bends compared to the "terror birds" and thus do not allow strong raptor claws to be assumed, which can be interpreted as a further indication of a vegetable food base. According to the enormous body size, it is assumed that Brontornis inhabited more open landscapes, as has also been proven for the Santa Cruz formation .
Systematics
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Closer relationship of Brontornis after Agnolin 2007
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Brontornis is a genus of the family of extinct Brontornithidae is very large, flightless birds in the Miocene in South America were at home. Originally placed at the base of the Phorusrhacidae ("terror birds"), the Brontornithidae , according to recent cladistic studies, form a closer family group with the geese birds and belong to the basal group of this order . The reasons for this are to be found in the structure of the skull, for example in the design of the lower jaw and the square leg, and in the structure of the rear extremities, whereby the Brontornithidae can be relegated to the vicinity of the Gastornithidae and Dromornithidae . Since the introduction of the Brontornithidae as a family group, this has mostly been considered monotypical , but Liornis , which was originally regarded as a synonym for Brontornis and later Phorusrhacos , represents a very original representative within this group of birds. The discovery of a Tibiotarsus from Salla-Luribay in Bolivia , which is similar to that of Brontornis and, as in this one, due to the lack of a conspicuous bone web (pons supratendineus) at the lower joint end, deviates significantly from that of the Phorusrhacidae, dates back to the Oligocene and could thus represent the oldest known representative of the Brontornithidae.
The first description of Brontornis was in 1891 by Francisco Moreno and Alcide Mercerat using a few leg bones. They placed Brontornis in their own family of Brontornithidae within the newly created order of Stereornithes. At that time this also comprised the Phorusrhacidae as an independent family, but according to Moreno and Mercerat the order showed strong similarities to the geese birds and, in their opinion, stood at the transition to the duck birds . Within the genus, one species is recognized with B. burmeisteri , another species established by Florentino Ameghino in 1895, B. platyonyx , is now considered a synonym, as is the species Rostroornis floweri , which Moreno and Mercerat established in the same year as Brontornis . The lectotype of the genus and type species (copy number MLP 88-91) comprises a femur , a tibiotarsus , a fibula and a tarsometatarsus of an individual and was only established in 1967 by F. Brodkorb.
"Terror bird" or goose relative - On the debate about the systematic classification
Traditionally, Brontornis as a genus was usually assigned to the extinct family of Phorusrhacidae ("terror birds"), which was quite widespread in South America and includes large to very large, mostly predatory ratites. These are related to the recent Seriemas ( Cariama ), special characteristics are, among other things, the hook-shaped downwardly curved upper beak and the curved terminal phalanges, which had sharp claws and thus distinguish the birds as predatory carnivores. Within the terror birds, Brontornis was relegated to its own subfamily Brontornithinae, very large and massive birds, which also included Physornis and Paraphysornis . The allocation to the Phorusrhaciden was mainly based on the development of the strong mandibular symphysis as well as the front and rear narrowed tarsometatarsus and was supported by an examination of the entire family by Herculano MF Alvarenga and Elizabeth Höfling in 2003.
A revision of the genus Brontornis by Federico L. Agnolin in 2007 rejects the assignment to the Phorusrhacids based on these characteristics, since they also occur in other early large ratites, such as Gastornis or within the Dromornithidae . The rotation of the middle shaft of the tibiotarsus and the construction of the square leg suggest a closer relationship with the goose birds (Anseriformes). For these reasons, Agnolin 's Brontornis was excluded from the Phorusrhaciden and moved to the base of the geese birds. Physornis and Paraphysornis, on the other hand, are still counted among the "terror birds" and now form the new subfamily Physornithinae . Such a position for Brontornis had originally been favored by the first descriptors of the genus, and Matilde Dolgopol de Saez had also excluded Brontornis from the Phorusrhacids in 1927 for similar considerations and assigned it to the goose birds, assuming a close relationship with Gastornis . In the period following Agnolin's revision, his decision met with some approval from experts.
Another phylogenetic analysis of the Phorusrhacidae in 2011 included Brontornis again, which was justified by the special characteristic of a fragmented thoracic vertebra. In the following time Brontornis was still listed as a member of the goose birds, but the reintegration into the Phorusrhacidae found little echo in science. Further cladistic analyzes, which mainly concerned the structure of the walking legs - these are similar to those of today's swan ( Cygnus ) from the family of ducks (Anatidae) - confirmed the position of Brontornis at the base of the phylogenetic development of the geese. Furthermore, the different construction of the lower jaw, which is short and robust in Brontornis , but long and slender in the "terror birds", can be seen as an indication of a separation from one another. According to the studies already mentioned, the different design of the lower jaw also results in a different diet of Brontornis compared to the Phorusrhaciden.
literature
- Federico L. Agnolin: Brontornis burmeisteri Moreno & Mercerat, un Anseriformes (Aves) gigante del Mioceno Medio de Patagonia, Argentina. Revista del Museo Argentino de Ciencias Naturales Nueva Series 9, 2007, pp. 15-25
- Herculano MF Alvarenga and Elizabeth Höfling: Systematic revision of the Phorusrhacidae (Aves: Ralliformes) . Papéis Avulsos de Zoologia, 43 (4): 55-91, Sao Paulo 2003. PDF
Individual evidence
- ↑ a b c d Eric Buffetaut: The Brontornithidae: New data about an old palaeontological riddle. In: M. Delfino, G. Carnevale and M. Pavia (Eds.): Abstract Book and Field Trip Guide, XII Annual Meeting of the European Association of Vertebrate Palaeontologists 24-28 June 2014. Museo Regionale di Scienze Naturali, Regione Piemonte, Torino, 2014, p. 33
- ↑ a b c d e f g Eric Buffetaut: 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), 2014, pp. 207-214
- ↑ a b c d e f g h Herculano MF Alvarenga and Elizabeth Höfling: Systematic revision of the Phorusrhacidae (Aves: Ralliformes). Papéis Avulsos de Zoologia 43 (4), 2003, pp. 55-91 PDF
- ↑ a b c d e f g h Federico L. Agnolin: Brontornis burmeisteri Moreno & Mercerat, un Anseriformes (Aves) gigante del Mioceno Medio de Patagonia, Argentina. Revista del Museo Argentino de Ciencias Naturales Nueva Series 9, 2007, pp. 15-25
- ↑ Gerald Mayr: Cariamae (seriemas and allies). In: Gerald Mayr (Ed.): Paleogene Fossil Birds. Springer, 2009, pp. 139–152 (p. 140)
- ↑ a b c Federico J. Degrange, Jorge I. Noriega and Juan I. Areta: Diversity and paleobiology of the Santacruzian birds. In: Sergio F. Vizcaíno, Richard F. Kay and M. Susana Bargo (eds.): Early Miocene paleobiology in Patagonia. High-latitude paleocommunities of the Santa Cruz Formation. Cambridge University Press, New York, 2012, pp. 138-155
- ↑ SJJF Davies: birds Elephant. In: Michael Hutchins: Grzimek's Animal Life Encyclopedia. 8 Birds I Tinamous and Ratites to Hoatzins (2 ed.). Farmington Hills, MI: Gale Group, 2003, pp. 103-104. ISBN 0-7876-5784-0
- ^ Peter F. Murray: Magnificent Mihirungs: The Colossal Flightless Birds of the Australian Dreamtime. Indiana University Press, 2003, p. 203
- ^ A b c Claudia P. Tambussi and Federico J. Degrange: Neogene Birds of South America. In: Claudia P. Tambussi and Federico J. Degrange (Eds.): South American and Antarctic Continental Cenozoic Birds. Paleobiogeographic Affinities and Disparities. SpringerBriefs in Earth System Sciences, 2013, pp. 59–86 (pp. 64–65)
- ↑ a b Herculano Alvarenga, Luis Chiappe and Sara Bertelli: Phorusracids: The Terror birds. Gareth Dyke and Gary Kaiser (Eds.): Living Dinosaurs: The History and evolution of modern birds. John Wilex & Sons Ltd., 2011, pp. 187-203
- ↑ a b c P. Brodkorb: Catalog of fossil birds, Part III (Ralliformes, Ichthyornithiformes, Charadriiformes). Bulletin of Florida State Museum 2, 1967, pp. 99–220 ( [1] )
- ↑ Francisco P. Moreno and Alcide Mercerat: Catálogo de los pájaros fósiles de la República Argentina conservados en el Museo de La Plata . Anales del Museo de La Plata, Paleontología Argentina 1, 1891, pp. 7–71 ( [2] )
- ↑ Claudia P. Tambussi: 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, 2011, pp. 458-474
- ↑ Marcos D. Ercoli, Francisco J. Prevosti and Analía M. Forasiepi: The Structure of the Mammalian Predator Guild in the Santa Cruz Formation (Late Early Miocene). Journal of Mammal Evolution 2013 doi : 10.1007 / s10914-013-9243-4
