Leporinus scalabrinii

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Leporinus scalabrinii
Temporal occurrence
Late Miocene ( Huyaquerian )
approx. 9 to 6 million years
Locations
Systematics
Sub-cohort : Ostariophysi
Otophysa
Order : Tetras (Characiformes)
Family : Narrow-mouth tetra (Anostomidae)
Genre : Leporinus
Type : Leporinus scalabrinii
Scientific name
Leporinus scalabrinii
( Ameghino , 1898)

Leporinus scalabrinii is an extinct species of the narrow-mouthed tetra (Anostomidae) thatlivedin South America in the late Miocene . It was a typical member of the genus Leporinus , a group of medium-sized, omnivorous freshwater fish. The only known remnant to date includes a fossil skull from the Argentine Ituzaingó Formation and estimated to be 6 to 9 million years old. It was discovered at the end of the 19th century and described by Florentino Ameghino as Arrhinolemur scalabrinii , a relative of the lemurs , and later placed in its own mammal order . After several paleontologists expressed doubts about this assignmentfrom the middle of the 20th century, a detailed revision of the fossil came to the conclusion that it was a bony fish, which in phylogenetic analyzes forms the sister species of the bream tetra ( Abramites hypselonotus ).

features

The skull of Leporinus scalabrinii shows all the typical features of the narrow-mouthed tetra, including the narrowed, non-protruding mouth opening. The head shape largely coincided with that of Leporinus striatus . His upper jaw probably had 12 to 14 teeth in both jaws. There were three of them on each side in the premaxilla , a feature that is otherwise only found in the bream tetra and L. striatus . The skull of L. scalabrinii differs from the latter in that the fontanel closes between the frontal and parietal bones . The clearest difference to the bream tetra is the tooth shape in the dental; which is more chisel-shaped in L. scalabrinii and spatula-sickle-shaped in the bream tetra. Further possible skull features cannot be determined because the fossilized bones are strongly embedded in a sediment matrix that can hardly be removed without damaging the fossil.

Site, fossil material and stratigraphy

The holotype and only find of Leporinus scalabrinii (a largely preserved skull with the inventory number MACN A-9880, embedded in a sediment matrix, with the inventory number MACN A-9880) was found around 1897 by Pedro Scalabrini , who left it to Florentino Ameghino. The information about the discovery of the fossil does not go beyond this information. Analysis of other pieces from the same period and region, in conjunction with the matrix, however, suggests that the find came from the Ituzaingó formation on the steep bank of the Río Paraná . The oldest layers of this formation are dated to nine, the youngest layers to six million years, which means that it falls into the late Miocene. The corresponding chronostratographic level for South America is the Huyaquerium .

Paleoecology

All that is known about the paleoecology of Leporinus scalabrinii is that it is a freshwater fish that probably lived in a forerunner of the Río Paraná. Its closest recent relatives feed omnivorously on aquatic plants and small invertebrates.

Systematics and taxonomy

Drawing of a mammalian skull in plan and side view
Florentino Ameghinos reconstruction of the holotype as a mammal. Ameghino first placed the animal as Arrhinolemur scalabrinii in the vicinity of the lemurs , later in a separate order Arrhinolemuroidea, which should underline its peculiarity.

Florentino Ameghino had difficulties identifying the fossil skull when it was first described in 1898. At that time, the find was still heavily covered by sediment and thus eluded a detailed investigation; Ameghino may have only examined the fossil superficially. He came to the conclusion that it must be the skull of a mammal belonging to the lemur family that had a greatly reduced nasal bone. Consequently, he gave the species the name Arrhinolemur scalabrinii ("Scalabrini's nasal lemur") and placed it in the vicinity of the extinct genus Necrolemur . At the same time, however, he also expressed doubts about this classification: Although the skull shape is reminiscent of lemurs, some fine osteological features have no correspondence among the taxa known to him. After he had largely cleaned the skull of the sediments adhering to it, he came to the conclusion that the species must represent a separate order of mammals, for which he introduced the name Arrhinolemuroidea in 1899.

In the absence of a revision, this classification remained for around 50 years. When George Gaylord Simpson re-examined the holotype in 1945 for a reclassification of mammals, he rejected Ameghino's determination: it was by no means a mammal, but rather a fish. Alvaro Mones reiterated this conclusion in 1987 and expressed the view that the species could be a real tetra . Nevertheless, it took another 25 years before a comprehensive revision of the fossil came to the conclusion that it must be a narrow mouth tetra. The authors of this study, Sergio Bogan , Brian L. Sidlauskas , Richard P. Vari and Federico Agnolin compared the skull with those of recent narrow-mouth tetra species and classified it as Leporinus scalabrinii in the paraphyletic genus Leporinus , where it is the sister species of the bream tetra ( Abramites hypselonotus ) forms. Both species face Leporinus striatus as sister clade .

swell

literature

  • Florentino Ameghino: Sur Arhinolemur, genre du tertiaire de Parana, representative of a type nouveau de la classe des Mammifières. In: Comptes rendus hebdomadaires des séances de l'Académie des sciences 127, 1898. pp. 395-396.
  • Florentino Ameghino: Los Arrhinolemuroidea, un nuevo orden de mamíferos extinguidos. In: Comunicaciones del Museo Nacional de Buenos Aires 1, 1899. pp. 146–151. ( Full text ; PDF; 29.8 MB)
  • Sergio Bogan, Brian L. Sidlauskas, Richard P. Vari, Federico Agnolin: Arrhinolemur scalabrinii Ameghino, 1898, of the Late Miocene - A Taxonomic Journey from the Mammalia to the Anostomidae (Ostariophysi: Characiformes). In: Neotropical Ichthyology 10 (3), 2012. pp. 555-560. ( Full text ; PDF; 1.8 MB)
  • Alberto Luis Cione, Wasila M. Dahdul, John G. Lundberg, Antonio Machado-Allison: Megapiranha paranensis, a New Genus and Species of Serrasalmidae (Characiformes, Teleostei) from the Upper Miocene of Argentina. In: Journal of Vertebrate Paleontology 29 (2), 2009. doi : 10.1671 / 039.029.0221 , pp. 350-358.
  • Brian L. Sidlauskas, Richard P. Vari: Phylogenetic Relationships within the South American Fish Family Anostomidae (Teleostei, Ostariophysi, Characiformes). In: Zoological Journal of the Linnean Society 154 (1), 2008. doi : 10.1111 / j.1096-3642.2008.00407.x , pp. 70-210.
  • George Gaylord Simpson: The Principles of Classification and a Classification of Mammals. In: Bulletin of the American Museum of Natural History 85, 1945. pp. 1-350.

Web links

Commons : Leporinus scalabrinii  - collection of images, videos and audio files

Individual evidence

  1. ↑ a b Ameghino 1898, p. 395.
  2. ↑ Sidlauskas & Vari 2008, p. 39.
  3. ↑ Bogan et al. 2012, pp. 557-558.
  4. ↑ Cione et al. 2009, p. 351.
  5. ↑ Bogan et al. 2012, pp. 555-556.
  6. ↑ Bogan et al. 2012, p. 556.
  7. ↑ Cione et al. 2009, p. 71.
  8. ↑ Bogan et al. 2012, p. 555.
  9. ↑ Ameghino 1898, pp. 395-396.
  10. ↑ Ameghino 1899, p. 151.
  11. ↑ Simpson 1945, p. 184.
  12. ↑ Bogan et al. 2012, pp. 555-559.