Sahonachelys mailakavava: Cretaceous Turtle from Madagascar Had Adaptations for Suction Feeding
Sahonachelys mailakavava, a newly-identified species of pelomedusoid turtle from the Late Cretaceous of Madagascar, had an unusually flattened skull, a particularly gracile lower jaw, and enlarged tongue bones, which not only gave it a frog-like appearance, but also suggest that it was a specialized, aquatic suction feeder that fed upon moving prey.
Sahonachelys mailakavava lived in what is now Madagascar during the Maastrichtian age of the Late Cretaceous epoch, between 72 and 66 million years ago.
As in all modern turtles, the ancient species lacks teeth, but in addition the surfaces at the upper and lower jaws that face toward each other are poorly developed, showing that the turtle did not use its jaws to process food, but instead swallowed prey whole, which is typical for suction feeders.
It likely fed on small-bodied living prey, such as insect larvae, fish fry, and tadpoles using quick strikes.
“Sahonachelys mailakavava is a stunning example of evolution in isolation,” said Dr. David Krause, a paleontologist in the Department of Earth Sciences at the Denver Museum of Nature & Science and the Department of Anatomical Sciences at Stony Brook University.
“It represents a lineage that evolved on Madagascar for over 20 million years and joins a litany of other bizarre Late Cretaceous vertebrate animals that we’ve found on the island.”
“This specimen is, by far, the best turtle fossil we discovered during the 28 years of conducting field research there.”
A nearly complete skeleton of Sahonachelys mailakavava was discovered in June 2015 in the Maevarano Formation in northwestern Madagascar.
“This is the best-preserved turtle of the entire Late Cretaceous of the southern continents and as such very significant in terms of reconstructing its way of life and relationships with other turtles,” noted Professor Walter Joyce, a paleontologist in the Department of Earth Sciences at the University of Freiburg.
The paleontological fauna of Madagascar is known for animals that are very specialized, which is in part due to its long isolation from surrounding continents.
Sahonachelys mailakavava shows that the Malagasy fauna was already unique in the Late Cretaceous epoch.
The ancient turtle is the only representative of its group to have evolved suction feeding, which is otherwise only known in distant relatives, so-called snake-necked turtles.
“As palaeontologists, we try to understand the biology and evolution of past life,” said Dr. Serjoscha Evers, also from the Department of Earth Sciences at the University of Freiburg.
“Fossils like this give a wealth of information that is not always present.”
“The identification of suction feeding in a new turtle lineage is exciting and was unexpected.”
“It shows how animals evolve similar traits for similar functions, even if they are only distantly related.”
A paper describing the discovery was published in the journal Royal Society Open Science.
Walter G. Joyce et al. 2021. A new pelomedusoid turtle, Sahonachelys mailakavava, from the Late Cretaceous of Madagascar provides evidence for convergent evolution of specialized suction feeding among pleurodires. R. Soc. open sci 8 (5): 210098; doi: 10.1098/rsos.210098