Saturday Science: They Ate Clams

You don't think of Peru as a place to find crocodiles, and these days, you'd be right. Thirteen million years ago, however:

Thirteen million years ago, as many as seven different species of crocodiles hunted in the swampy waters of what is now northeastern Peru, new research shows. This hyperdiverse assemblage, revealed through more than a decade of work in Amazon bone beds, contains the largest number of crocodile species co-existing in one place at any time in Earth's history, likely due to an abundant food source that forms only a small part of modern crocodile diets: mollusks like clams and snails. The work, published today in the journal Proceedings of the Royal Society B, helps fill in gaps in understanding the history of the Amazon's remarkably rich biodiversity. . . .

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. But although invertebrates like mollusks and crustaceans are abundant in Amazonian fossil deposits, evidence of vertebrates other than fish have been very rare.

We should keep in mind that the eastern range of the Andes, the area in question, only began to form about 10 million years ago, much later than the western, coastal ranges. The Amazon River itself only started forming 11 million years ago, so the present configuration of the whole area is fairly new.

So, 13 million years ago, the Amazon basin was a swamp full of crocodiles digging for clams.

This model is a life reconstruction of the head of Gnatusuchus pebasensis, a 13-million-year-old, short-faced crocodile with globular teeth that was thought to use its snout to "shovel" mud bottoms, digging for clams and other mollusks. Model by Kevin Montalbán-Rivera.

Credit: Copyright Aldo Benites-Palomino

Something to think about.