How many species of crocodiles can co-exist in close proximity? Well, some 13 million years ago, as many as seven different species lived and hunted in the swampy waters of Peru, says a research.
This is the largest number of crocodile species co-existing in one place at any time in earth's history, probably thanks to an abundant food source - molluscs like clams and snails.
The work helps fill in gaps in understanding the history of the Amazon's remarkably rich biodiversity.
"We uncovered this special moment in time when the ancient mega-wetland ecosystem reached its peak in size and complexity, just before its demise and the start of the modern Amazon River system," said lead author of the paper, Rodolfo Salas-Gismondi, from National University of San Marcos, Peru.
Before the Amazon basin had its river, which formed about 10.5 million years ago, it contained a massive wetland system, filled with lakes, embayments, swamps, and rivers that drained northward toward the Caribbean, instead of today's pattern of eastward river flow to the Atlantic Ocean.
Knowing the kind of life that existed at that time is crucial to understanding the history and origins of modern Amazonian biodiversity.
Three of the species are entirely new to science, the strangest of which is Gnatusuchus pebasensis, a short-faced caiman with globular teeth that is thought to have used its snout to "shovel" mud bottoms, digging for clams and other molluscs.
"When we analysed Gnatusuchus bones, we knew it was a milestone for understanding proto-Amazonian wetland feeding dynamics," Salas-Gismondi said.
The new research suggests that with the inception of the Amazon River System, mollusc populations declined and durophagous crocodile species went extinct as caimans with a broader palate diversified into the generalist feeders that dominate the modern Amazonian ecosystems.
Today, six species of caimans live in the whole Amazon basin, although only three ever co-exist in the same area and they rarely share the same habitats.
The findings were published in the journal Proceedings of the Royal Society B.
