A new pelomedusoid turtle, Sahonachelys mailakavava, from the Late Cretaceous of Madagascar provides evidence for convergent evolution of specialized suction feeding among pleurodires.

Abstract

The Maevarano Formation in northwestern Madagascar has yielded a series of exceptional fossils over the course of the last three decades that provide important insights into the evolution of insular ecosystems during the latest Cretaceous (Maastrichtian). We here describe a new genus and species of pelomedusoid turtle from this formation, Sahonachelys mailakavava, based on a nearly complete skeleton. A phylogenetic analysis suggests close affinities of Sahonachelys mailakavava with the coeval Madagascan Sokatra antitra. These two taxa are the only known representatives of the newly recognized clade Sahonachelyidae, which is sister to the speciose clade formed by Bothremydidae and Podocnemidoidae. A close relationship with coeval Indian turtles of the clade Kurmademydini is notably absent. A functional assessment suggests that Sahonachelys mailakavava was a specialized suction feeder that preyed upon small-bodied invertebrates and vertebrates. This is a unique feeding strategy among crown pelomedusoids that is convergent upon that documented in numerous other clades of turtles and that highlights the distinct evolutionary pathways taken by Madagascan vertebrates.