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Snout-nosed crocodiles with jaws strong enough to crush clam shells ruled the swampy wetlands that covered Peru 13 million years ago.

Palaeontologists have discovered the remains of seven different species of crocodile and cayman, including three new species, in the area around the modern Amazon river.

The fossils were found in the Pebas district of northern Peru.

The new species of caymen Gnatusuchus pebasensis (shown in the reconstruction above) had a short but wide jaw that was powerful enough to crush clams and other shell fish. It used its snout to dig in the mud

One of the new species, named Gnatusuchus pebasensis, had blunt, peg-like teeth and used its broad snout to dig shellfish from the muddy swamp floor.

It grew up to 5.2ft (1.6 metres) in length and had just 11 teeth. Most cayman, which are related to alligators, tend to have around 20 teeth.

Another blunt nosed crocodile was named Kuttanacaiman iquitosensis, which means 'grinding or crushing machine'.

The scientists estimate it grew up to 6.2ft (1.9 metres) in length.

However, these new species were dwarved by two other previously known species of giant cayman whose fossils were also found nearby.

Purussaurus neivensis and Mourasuchus atopus are thought to have grown up to 39ft (12 metres) in length and were more generalised predators.

The researchers say that it is highly unusual to have found a habitat that had so many species of cayman living alongside each other.

There are six cayman species that live in the whole of the Amazon basin today, but only three are ever found in the same area and they rarely share the same habitat.

The large number of cayman found in Pebas has been described by the researchers leading the excavation as 'hyperdiverse'.

Dr Rodolfo Salas Gismondi, from the University of Montpelier in France, said the huge wetland habitat that covered the area led to an explosion in the number of crocodile species.

He said: 'We have uncovered this special momen in time when the ancient mega-wetaland ecosystem reached its peak in size and complexity, just before its demise and the start of the modern Amazon River system.

'At this moment, most known cayman groups co-existed. 

'Ancient lineages bearing unusual blunt snouts and globular teeth along with those more generalised feeders representing the beginning of what was to come.'

The fossils may now help scientists unravel the evolutionary origins of cayman that live in the Amazon basin.

They describe the discovery in a paper published in the journal Proceedings of the Royal Society B.  

Scientists found fossilised remains of seven ancient caymen species in Pebas, northern Peru, shown above

The fossilised skulls shown above belong to the three new snout nosed caymen species Gnatusuchus pebasensis (a) Kuttanacaiman iquitosensis (b) and the much larger Caiman wannlangstoni (c)

The Gnatusuchus pebasensis name is derived from 'Natu', which is Quechua for 'small nose', along with the name of the village where it was found, Pebas, and the Greek for crocodile - Souchos.

The animal, which is new to science, is thought to have used its snout as a shovel in to search for shellfish in the muddy depths of the swamps.

Dr Salas Gismondi said: 'When we analysed Gnatusuchus bones and realised that it was probably a head-burrowing and shovelling caiman preying on mollusks living in muddy river and swamp bottoms, we knew it was a milestone for understanding proto-Amazonian wetland feeding dynamics.'

The scientists also describe a third new species of prehistoric caymen called Caiman wannlangstoni, which they estimate grew up to 7ft (2.2 metres) long.

It is thought to have resembled the broad-snouted caymen that lives in fresh water marshes and swamps thought out central and eastern south America. 

Caiman wannlangstoni, one of the new species, resembled the broad snouted caymen pictured above