fossils

Crocodile fossils reveal parallel evolution in India and Amazon

3986b46bb4f35aa1ff4d42167a12e0fc

Vasika
Udurawane

Writer
34f1d64c52c45a6bdce31bc5e48b86cc

Julio
Lacerda

Staff Artist and Writer
The highly endangered and long-snouted gharial lives in the Indian Subcontinent. But millions of years ago, these creatures ruled the waterways of the world, including the Amazonian region. And it is here that we can further unravel the secrets behind their long evolution. Enter “the storyteller.”

Gryposuchus existed as a genus in the ancient Amazonian and Caribbean regions for millions of years. Numerous species have been found, and they vary quite remarkably in size. They are known from snouts and skull remains, with one species, the massive Gryposuchus croizati stretching 10 meters (33 ft) in length. While some were among the true giants of the crocodilian world, others were quite ordinary in size.


For all their superficial differences though, these ancient and modern gharials all have very long snouts and “telescoped” eye openings for their river-dwelling lifestyle. This helped them to see and catch fish in their habitat, and these eye openings crop up time and again in these gharials.


Yet for a long time, we didn’t know if it was an example of convergent evolution or whether it was a common evolutionary feature. A new species of Gryposuchus, Gryposuchus pachakumae has been found in Peru and it is the oldest known gavialoid crocodylian from the Amazon.


During the middle of the Miocene, around 13 million years ago, this area was a huge lake-like wetland area with numerous species of animals, including a number of crocodiles. And Gryposuchus was the only long-snouted fish-eater among them.


It gets its species name from the South American storyteller deity Pachakumae. This new species, affectionately nicknamed “the storyteller” lacks “telescoped” orbits, unlike the other ancient gharials of the time.


This in itself is an odd feature, for all gharials have these telescoped eye openings. However, the skull is quite complete, so it is easier to ascertain the relationships of the animal and solve a great evolutionary puzzle that has boggled the minds of researchers for years. The lack of telescoped orbits may represent an ancestral condition of the South American gharials. This new species and other Gryposuchus possibly evolved in parallel with the Indian gharials. Their similar habits led to convergent evolution.


The exact evolutionary relationships of the modern gharial of the Indian Subcontinent, Gavialis gangeticus, have been tough to resolve and scientists are still trying to put these issues to rest. Researchers don’t know where the modern gharial and the slightly broader-snouted false gharial Tomistoma schlegelii diverged from one another. We do, however have a number of remains of these ancient creatures, with “the storyteller” adding to an ever-growing list of fossils.


The very oldest gharials date back to the Late Cretaceous of North America and many more appear all over the world in the fossil record. One of the best-known of all fossil gharials is of course, the South American Gryposuchus.


Original research published April 20, 2016, in PLOS ONE by Rodolfo Salas-Gismondi from the Université de Montpellier, France, and colleagues.

3986b46bb4f35aa1ff4d42167a12e0fc

Vasika
Udurawane

Writer


http://sulc.us/0mptl
http://www.eartharchives.org/articles/crocodile-fossils-reveal-parallel-evolution-in-india-and-amazon/