The above is a red-bellied piranha, Pygocentrus nattereri (formerly Serrasalmus nattereri). It is NOT the man-eater it is made out to be!
Note that piranhas are known to eat hatchling spectacled caimans, so it is likely that some Paleosuchus hatchlings would suffer the same fate. As the caiman grow, though, they get their revenge!
The red-bellied piranha is the common name for 3 different species of piranha: Pygocentrus nattereri (from the Amazon and its drainages), Pygocentrus piraya (which is a 2 foot long version of the genus, from Rio Sao Francisco only), and Pygocentrus caribe (from the Orinoco and its drainages).
Other notorious species are members of the serrasalmus genus, but do not have the same reputation as the Pygocentrus species.
Interesting fact #1: Piranhas replace their teeth throughout their life - like crocodilians. However, instead of replacing them one by one, they shed them in quarters. By this I mean that they will lose all teeth in say the bottom left quarter of the jaw, then maybe the right upper quarter etc. In this way, they will only ever have a quarter of their jaw 'toothless' at most. The new teeth grow within a couple of days. The reason for this type of shedding is due to the dental anatomy of the piranha. Each tooth interlocks with the teeth on either side of it. This means that there is NO gap of gumline between the teeth, so there is a continuos cutting edge. This enables them to cleanly clip out chunks of flesh from their prey.
Needless to say, the teeth are razor sharp, and very hard, so they maintain this knife-edge.