Scientists may have discovered a 13-million-year-old crocodilian that may tell them a bit more about the evolution of eyes. The new findings reveal how South American and Indian species evolved separately to acquire protruding, "telescoped" eyes.
In this case, researchers unearthed a gavialoid, which is one of the three major types of crocodilians. Known for their elongated, narrow snouts and sharp, piercing teeth, gavialoids are a diverse group of mostly extinct crocodilians that lived in tropical regions. Many evolutionary relationships between these species, though, remain unclear.
In this latest study, researchers decided to take a closer look at the fossil in order to better understand its evolutionary roots. In this case, the species is the oldest-known gavialoid crocodilian to be found from the Amazon. Named Gryposuchus pachakamue, the animal lived in wetlands that contained lakes, embayments and swamps that drained north toward the Caribbean.
"Gryposuchus pachakamue was distinct from all the other crocodiles living in the vast Pebas Mega-Wetlands of northern South America," said Rodolfo Salas-Gismondi of France's University of Montpellier, lead author of the new study. "The new gavialoid was the only long-snouted species within a hyper-diverse crocodile community dominated by blunt-snouted, clam-eating caimans."
After analyzing the crocodilian, researchers found that this particular specimen probably represents the ancestral condition form which the South American lineage evolved protruding eyes. This means that the distinctive eyes of gavialoids evolved in parallel in South American and Indian groups. At first, they just showed slight telescoping, as seen in this newly discovered specimen. However, they then became fully telescoped during the evolution of other members of the lineage. Later, species adopted a river-dwelling lifestyle, and it's likely that the telescoped eyes were adaptive, helping them to catch fish in these habitats.
"The extraordinarily well-preserved fossils of this new 13-million-year-old gharial document how independent, parallel evolution of long-snouted animals with specialized visual systems occurred across continents," said John Flynn of the American Museum of Natural History in New York and an author on the paper. "Continued paleontological exploration of the Amazon Basin is essential for discovering fossils that reveal more about the origins and history of tropical South America's extraordinarily rich modern biological communities and habitats."
The findings were published in the April edition of the journal PLOS One.
