Megapiranha

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Megapiranha
Temporal range: Late Miocene (Huayquerian)
~9.0–6.8  Ma
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Megapiranha Colossoma.jpg
Comparison of M. paranensis and the tambaqui
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Characiformes
Family: Serrasalmidae
Genus: Megapiranha
Cione et al. 2009
Species:
M. paranensis
Binomial name
Megapiranha paranensis
Cione et al. 2009

Megapiranha is an extinct serrasalmid characin fish from the Late Miocene (8–10 million years ago) Ituzaingó Formation of Argentina, described in 2009. [1] The type species is M. paranensis. [2] It is thought to have been about 71 centimetres (28 in) in length and 10 kilograms (22 lb) in weight. [3] The holotype consists only of premaxillae and a zigzag tooth row; the rest of its body is unknown. [4] This dentition is reminiscent of both the double-row seen in pacus, and the single row seen in the teeth of modern piranhas, suggesting that M. paranensis is a transitional form. Its bite force is estimated between 1,240–4,749  N (279–1,068 lbf). [3]

Contents

History and naming

The holotype of Megapiranha was discovered in an unknown locality of the Ituzaingó Formation, Argentina, in the early 20th century near the towns of Paraná and Villa Urquiza. The specimen, a fragment of the animal's premaxilla containing several teeth, was later rediscovered by Alberto Luis Cione in the collection of the Museo de La Plata. An isolated tooth discovered in 1999 has also been referred to this genus. [4]

The name Megapiranha is a combination of the word "mega" in reference to the animal's large size and piranha, a common name for typically carnivorous members of Serrasalmidae. The word piranha itself is a Portuguese merging of words originating in the Tupi language and may have several meanings including "tooth fish", [5] "cutting fish", "devil fish" [6] or "biting fish". [7] The species name was chosen to reflect Megapiranha's place of origin near the city of Paraná. [4]

Description

Skeletal reconstruction of Megapiranha with a 10 cm scale bar. MegapiranhaSkeletal.jpg
Skeletal reconstruction of Megapiranha with a 10 cm scale bar.

Although only three teeth are fully preserved, the holotype specimen shows the presence of seven premaxillary teeth which are arranged in a zig-zag pattern with some overlap. The third, fourth and fifth tooth are preserved and all share very similar morphology with one another. Of these teeth the first and third formed the inner row, while the rest formed the outer row. In other serrasalmids the teeth are arranged either two rows of seven teeth with a morphologically distinct second tooth of the inner row (third tooth), such an arrangement is seen in the Tambaqui for instance, a zig-zag pattern of five teeth (like in Catoprion ) or a single row of six teeth, which is typical for the carnivorous species. [4]

Each teeth only shows a single tooth crown the shape of an almost equilateral triangle, which sits atop a constriction of the tooth. Towards the apex of the crown the teeth take on a more sloping edge which is finely serrated in addition to slight labio-lingual compression. Much like in the arrangement of the teeth, Megapiranha differs significantly from its modern relatives. Pacus generally have more complex and broad teeth while true piranhas have teeth with multiple cusps, well developed serration and strong compression, making them thin and well suited for cutting. Between the three preserved teeth the size varies greatly, with the third being the largest and the fourth the smallest. The attachment scars likewise differ in size, showing a similar size distribution. [4]

The preserved premaxilla is almost straight and the teeth are all positioned on the same horizontal plane. The dorsal surface of the bone is slightly concave and slopes upwards towards the front as it transitions to the ascending process, which is barely tapering. Here too Megapiranha provides a unique combination of features amongst its family, with serrasalmids that share the straight axis of the premaxilla typically having a straight dorsal margin and two different planes on which the teeth are placed, while those with a single horizontal plane and concave dorsal surface lack a straight axis. The entire premaxilla is 6.9 cm (2.7 in) long with a rugose outer surface that most likely housed nerves and blood vessels. The symphyseal joint is interlocking. [4]

Based on the size of the holotype, Megapiranha has originally been estimated to have reached a length of 95–128 cm (37–50 in) and a weight of 73 kg (161 lb), larger than any other member of the family, living or extinct. [4] Later research using Serrasalmus rhombeus as a basis arrived at a more conservative size estimate of 71 cm (28 in) long and 10 kg (22 lb) heavy. [3]

Phylogeny

FMIB 52288 Dentition of Piaractus nigripinnis (Cope) a, b, c, the premaxilry from below, within, and without, respectively d and e, the.jpeg
Piranha jaws.jpg
The teeth of Megapiranha represent an intermediate state between broad Pacu teeth and the serrated triangular teeth of derived piranhas

Megapiranha combines several traits known from more basal serrasalmids with those of derived members. Both the subcircular tooth attachment scars as well as the presence of seven, not six, teeth are in line with what is known from most members of the group, while the triangular shape of the crown, fine serration and slight labiolingual compression are more in line with the morphology seen in the teeth of true piranhas. The interdigitating symphyseal joint meanwhile draws parallels to basal pacus like Colossoma and Mylossoma , however differences in the structure of the joint between Megapiranha and extant forms suggests that this trait developed independently from one another. [4]

This unique combination of characters supports the idea that within serrasalmids an evolutionary trend led to the shift from double-rowed dentition with broad teeth to the single row of flattened teeth observed in piranhas. Megapiranha represents an intermediate form between the two, with triangular, slightly compressed teeth but maintaining two rows of teeth that are still relatively broad. [4]

Serrasalmidae

Paleobiology

In the 2009 description of the genus, Cione and colleagues suggest that the dentition of Megapiranha may not have been a direct adaptation towards carnivory and likely helped the animal with a wide range of food sources. Part of their reasoning for this is the broad range of diets found within serrasalmids, including many herbivorous and omnivorous forms in addition to carnivores, as well as the highly specialised wimple piranha which feeds primarily on the scales of other fish. [4]

In 2012 Justin R. Grubich and colleagues suggest that the dentition of Megapiranha may have been a transitional form between feeding on hard prey and specialising in slicing flesh. To arrive at this conclusion, they conducted extensive measurements of the bite force of the extant Serrasalmus rhombeus as a standin for its Miocene relative. With this method they calculated a bite force of 1240 Newton for the smaller estimates and 4749 Newton for the older, larger size estimates. Even the more conservative estimates would put the bite-force of Megapiranha four times higher than that of the largest extant piranha species. The authors additionally note that the fact that the measurements were taken on live animals may lead to underestimates caused by fatigue and stress. Furthermore, the measurements were restricted to the anterior bite-force, not including the potential of doubled bite-force along the lower jaw. This may result in forces between 2480 and 9498 Newton. [3]

Tests using a bronze-alloy replica of Megapiranha's dentition showed that it would be able to penetrate the thick outer layer of a bovine femur, the shell of a turtle and the armor of certain catfish species. They conclude by suggesting that Megapiranha could have hypothetically fed on hard-shelled animals such as turtles, armored catfish and even attacked larger mammals. The shape of Megapiranha's teeth is inferred to effectively focus stress at the tip of the teeth while piercing flesh before distributing its impact stresses throughout the base of the tooth while crushing hard material such as bones in a similar fashion to how pacus crack hard-shelled fruits and nuts. However, this ecology is only hypothetical in the absence of any fossil material bearing the bite marks of Megapiranha. [3]

Related Research Articles

<span class="mw-page-title-main">Piranha</span> Common name for certain fishes of the family Serrasalmidae

A piranha or piraña is any of a number of freshwater fish species in the family Serrasalmidae, or the subfamily Serrasalminae within the tetra family, Characidae in order Characiformes. These fish inhabit South American rivers, floodplains, lakes and reservoirs. Although often described as extremely predatory and mainly feeding on fish, their dietary habits vary extensively, and they will also take plant material, leading to their classification as omnivorous.

<span class="mw-page-title-main">Megalodon</span> Extinct giant shark species from 23 to 3.6 million years ago

Otodus megalodon, commonly known as megalodon, is an extinct species of giant mackerel shark that lived approximately 23 to 3.6 million years ago (Mya), from the Early Miocene to the Early Pliocene epochs. O. megalodon was formerly thought to be a member of the family Lamnidae and a close relative of the great white shark, but has been reclassified into the extinct family Otodontidae, which diverged from the great white shark during the Early Cretaceous.

<i>Serrasalmus</i> Genus of fishes

Serrasalmus is a genus of piranhas. They are collectively known as pirambebas; the "typical" piranhas like the piraya piranha are nowadays placed in Pygocentrus. Like all piranhas, Serrasalmus are native to South America.

<i>Helicoprion</i> Genus of fossil fishes

Helicoprion is an extinct genus of shark-like eugeneodont fish. Almost all fossil specimens are of spirally arranged clusters of the individuals' teeth, called "tooth whorls", which in life were embedded in the lower jaw. As with most extinct cartilaginous fish, the skeleton is mostly unknown. Fossils of Helicoprion are known from a 20 million year timespan during the Permian period from the Artinskian stage of the Cisuralian to the Roadian stage of the Guadalupian. The closest living relatives of Helicoprion are the chimaeras, though their relationship is very distant. The unusual tooth arrangement is thought to have been an adaption for feeding on soft bodied prey, and may have functioned as a deshelling mechanism for hard bodied cephalopods such as nautiloids and ammonoids. In 2013, systematic revision of Helicoprion via morphometric analysis of the tooth whorls found only H. davisii, H. bessonowi and H. ergassaminon to be valid, with some of the larger tooth whorls being outliers.

<i>Pygocentrus piraya</i> Species of fish

Pygocentrus piraya, often called the piraya piranha or San Francisco piranha, and sometimes sold as the man-eating piranha, is a large, aggressive piranha from the São Francisco River basin in Brazil.

<span class="mw-page-title-main">Pacu</span> Common name for several species of fish

Pacu is a common name used to refer to several species of omnivorous South American freshwater serrasalmid fish related to piranhas. Pacu and piranha do not have similar teeth, the main difference being jaw alignment; piranha have pointed, razor-sharp teeth in a pronounced underbite, whereas pacu have squarer, straighter teeth and a less severe underbite, or a slight overbite. Pacu, unlike piranha, mainly feed on plant material and not flesh or scales. Additionally, the pacu can reach much larger sizes than piranha, at up to 1.08 m in total length and 40 kg (88 lb) in weight.

<span class="mw-page-title-main">Sharp-snouted piranha</span> Species of fish

The sharp-snouted piranha is a species of serrasalmid endemic to Peru. It is part of the S. rhombeus complex. It reaches a maximum size of around 7 inches (18 cm). Individuals often exhibit a red throat, similar to that of Pygocentrus nattereri. It is also known as ruby-throated diamond piranha or "ruby-red piranha"; the latter name is also used for the speckled piranha.

<span class="mw-page-title-main">Serrasalmidae</span> Family of fishes

The Serrasalmidae (serrasalmids) are a family of characiform fishes, recently elevated to family status. It includes more than 90 species. The name means "serrated salmon family", which refers to the serrated keel running along the belly of these fish. Fish classified as Serrasalmidae are also known by these common names: pacu, piranha, and silver dollar. These common names generally designate differing dental characteristics and feeding habits.

<i>Pliosaurus</i> Extinct genus of reptiles

Pliosaurus is an extinct genus of thalassophonean pliosaurid known from the Late Jurassic of Europe and South America. Most European species of Pliosaurus measured around 8 metres (26 ft) long and weighed about 5 metric tons, but P. rossicus and P. funkei would have been one of the largest plesiosaurs of all time, exceeding 10 metres (33 ft) in length. This genus has contained many species in the past but recent reviews found only six to be valid, while the validity of two additional species awaits a petition to the International Code of Zoological Nomenclature. Currently, P. brachyspondylus and P. macromerus are considered dubious, while P. portentificus is considered undiagnostic. Species of this genus are differentiated from other pliosaurids based on seven autapomorphies, including teeth that are triangular in cross section. Their diet would have included fish, cephalopods, and marine reptiles.

<i>Piaractus brachypomus</i> Species of fish

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References

  1. Live Science: Toothy 3-foot Piranha Fossil Found
  2. Megapiranha at Fossilworks.org
  3. 1 2 3 4 5 Grubich, J.R.; Huskey, S.; Crofts, S.; Orti, G.; Porto, J. (2012). "Mega-Bites: Extreme jaw forces of living and extinct piranhas (Serrasalmidae)". Scientific Reports. 2: 1009. Bibcode:2012NatSR...2E1009G. doi:10.1038/srep01009. PMC   3526859 . PMID   23259047.
  4. 1 2 3 4 5 6 7 8 9 10 Cione, Alberto Luis; Dahdul, Wasila M.; Lundberg, John G.; Machado-Allison, Antonio (2009). "Megapiranha paranensis, a new genus and species of Serrasalmidae (Characiformes, Teleostei) from the Upper Miocene of Argentina". Journal of Vertebrate Paleontology. 29 (2): 350. Bibcode:2009JVPal..29..350C. doi:10.1671/039.029.0221. S2CID   86046546. (Summary of the paper).
  5. Scientific American, "Fishing on the Amazon". Munn & Company. 6 November 1880. p. 293.
  6. Britton, A. Scott. Guaraní: Guaraní-English, English-Guaraní; concise dictionary. New York: Hippocrene Books, 2005. Print.
  7. "Piranha | Origin and meaning of piranha by Online Etymology Dictionary".