Researchers from Argentina, the United States and Venezuela have uncovered the jawbone of a striking transitional fossil that sheds light on this question. Named Megapiranha paranensis, this previously unknown fossil fish bridges the evolutionary gap between flesh-eating piranhas and their plant-eating cousins.
Present-day piranhas have a single row of triangular teeth, like the blade on a saw, explained the researchers. But their closest relatives — a group of fishes commonly known as pacus — have two rows of square teeth, presumably for crushing fruits and seeds. "In modern piranhas the teeth are arranged in a single file," said Wasila Dahdul, a visiting scientist at the National Evolutionary Synthesis Center in North Carolina. "But in the relatives of piranhas — which tend to be herbivorous fishes —the teeth are in two rows," said Dahdul.
Megapiranha shows an intermediate pattern: it's teeth are arranged in a zig-zag row. This suggests that the two rows in pacus were compressed to form a single row in piranhas. "It almost looks like the teeth are migrating from the second row into the first row," said John Lundberg, curator at the Academy of Natural Sciences in Philadelphia and a co-author of the study.
If this is so, Megapiranha may be an intermediate step in the long process that produced the piranha's distinctive bite. To find out where Megapiranha falls in the evolutionary tree for these fishes, Dahdul examined hundreds of specimens of modern piranhas and their relatives. "What's cool about this group of fish is their teeth have really distinctive features. A single tooth can tell you a lot about what species it is and what other fishes they're related to," said Dahdul. Her phylogenetic analysis confirms their hunch — Megapiranha seems to fit between piranhas and pacus in the fish family tree.
The Megapiranha fossil was originally collected in a riverside cliff in northeastern Argentina in the early 1900s, but remained unstudied until paleontologist Alberto Cione of Argentina's La Plata Museum rediscovered the startling specimen —an upper jaw with three unusually large and pointed teeth — in the 1980s in a museum drawer.
Cione's find suggests that Megapiranha lived between 8-10 million years ago in a South American river system known as the Paraná. But you wouldn't want to meet one today. If the jawbone of this fossil is any indication, Megapiranha was a big fish. By comparing the teeth and jaw to the same bones in present-day species, the researchers estimate that Megapiranha was up to 1 meter (3 feet) in length. That's at least four times as long as modern piranhas. Although no one is sure what Megapiranha ate, it probably had a diverse diet, said Cione.
Other riddles remain, however. "Piranhas have six teeth, but Megapiranha had seven," said Dahdul. "So what happened to the seventh tooth?"
"One of the teeth may have been lost," said Lundberg. "Or two of the original seven may have fused together over evolutionary time. It's an unanswered question. Maybe someday we'll find out."
The team's findings were published in the June 2009 issue of the Journal of Vertebrate Paleontology.
Citation: Cione, A., W. Dahdul, J. Lundberg, and A. Machado-Allison. (2009). "Megapiranha paranensis, a new genus and species of Serrasalmidae (Characiformes, Teleostei) from the upper Miocene of Argentina." Journal of Vertebrate Paleontology 29(2): 350-358.
The National Evolutionary Synthesis Center (NESCent) is an NSF-funded collaborative research center operated by Duke University, the University of North Carolina at Chapel Hill, and North Carolina State University.
Robin Ann Smith | EurekAlert!
New insights into the world of trypanosomes
23.08.2017 | Julius-Maximilians-Universität Würzburg
New Test for Rare Immunodeficiency
23.08.2017 | Universität Basel
Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.
As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...
Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.
Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...
For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.
While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...
An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.
The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...
A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.
Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...
16.08.2017 | Event News
04.08.2017 | Event News
26.07.2017 | Event News
22.08.2017 | Health and Medicine
22.08.2017 | Materials Sciences
22.08.2017 | Life Sciences