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Megapiranha

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Megapiranha
Fossil range: Late Miocene
Megapiranha Ray Troll
Megapiranha illustration by paleoartist Ray Troll.
Scientific classification

Class

Actinopterygii

Subclass

No information

Infraclass

Teleostei

Order

Characiformes

Suborder

No information

Family

Characidae

Subfamily

Serrasalminae
Géry, 1972

Genus

Megapiranha
Cione et al. 2009

Species

Megapiranha is a genus of extinct serrasalmid (Piranha) fish from the Late Miocene (between 8-10 million years ago) of Argentina described in 2009. Megapiranha reached lengths of up to 3 feet (1 meter) long, four times the size of the modern-day piranha. It is based on only premaxillae and teeth, with the rest of the body not known.[1]

HistoryEdit

The type specimen was originally collected in a riverside cliff in northeastern Argentina in the early 1900s. However, it remained in storage until paleontologist Alberto Cione of Argentina's La Plata Museum rediscovered the specimen in 1980s. The genus and species were formally described in the scientific literature in the Journal of Vertebrate Paleontology in 2009.[1]

Phylogenetic analysisEdit

The phylogenetic study performed was determined by parsimony analysis of morphological characters. The results showed that Megapiranha is the sister taxon to the piranha clade (Pygopristis, Pygocentrus, Pristobrycon, Serrasalmus). Two synapomorphies support this conclusion:[1]

  1. Triangular teeth in labial view with well-developed cutting edges.
  2. Serrations along both sides of tooth cutting edges.

Several plesiomorphic characters are also present in Megapiranha.

TeethEdit

Megapiranha teeth

The upper jaw of Megapiranha paranensis, showing intermediate tooth arrangement.

Megapiranha had seven premaxillary teeth with the first four arranged in a shallow, zig-zag row, and third tooth shaped similarly to the fourth and fifth teeth. Its teeth were finely serrated.[1]Megapiranha differs from modern-day piranhas in that its teeth are arranged in a zig-zag, intermediate pattern; a transitional form that bridges the evolutionary gap between flesh-eating piranhas and their plant-eating relatives. Present-day piranhas have a single row of teeth, while the piranhas relatives, the Pacu, have two rows of square teeth used for crushing fruits and seeds. The discovery of Megapiranha suggests that the two rows in pacu were compressed to form a single row in piranhas.[2][3] The teeth of Megapiranha also suggest that the creature was most likely omnivorous. Megapiranha also had seven teeth in its jaw, as opposed to the six teeth found in modern piranhas. However, the last (6th) tooth in modern piranhas is a compound tooth,[4] giving credence to the hypothesis that the seventh tooth seen in Megapiranha evolved into this compound tooth.[1][3]

ReferencesEdit

  1. ^ a b c d e Luis Cione et al. Megapiranha paranensis, a new genus and species of Serrasalmidae (Characiformes, Teleostei) from the Upper Miocene of Argentina. Journal of Vertebrate Paleontology, 2009; 29 (2): 350 doi:10.1671/039.029.0221
  2. ^ National Evolutionary Synthesis Center (NESCent). "New Fossil Tells How Piranhas Got Their Teeth." ScienceDaily 26 June 2009. 26 June 2009. http://www.sciencedaily.com /releases/2009/06/090625201822.htm.
  3. ^ a b "Toothy 3-foot Piranha Fossil Found". Live Science. 25 June 2009. http://www.livescience.com/animals/090625-megapiranha.html. Retrieved on June 26, 2009. 
  4. ^ Machado-Allison, A. 1983b. Estudios sobre la sistematica de la subfamilia Serrasalminae (Teleostei, Characidae). Parte II. Discusio´n sobre a condicio´n monofile´ tica de la subfamilia. Acta Biolo´ gica Venezuelica 11:145–195.

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