Pelomedusidae


Pelomedusidae is a family of freshwater turtles native to sub-Saharan Africa, with a single species, Pelomedusa subrufa, also found in Yemen. They range in size from in carapace length, and are generally roundish in shape. They are unable to fully withdraw their heads into their shells, instead drawing them to the side and folding them beneath the upper edge of their shells, hence are called African side-necked turtles.
The family contains two living genera. They are distinguished from their closest relatives by a hinge in the front section of the plastron.
Pelomedusidae spends most of its time in the mud at the bottom of rivers or shallow lakes, where they eat invertebrates, such as insects, mollusks, and worms. Many species aestivate through the dry season, burying themselves in the mud.
Some extinct species were fully marine. They became extinct due to competition with Caretta sea turtles.

Systematics and taxonomy

The related Podocnemididae is either treated as a distinct family or as a subfamily in the Pelomedusidae. The African side-necked turtles are then also demoted to subfamily rank, as the Pelomedusinae.
As taxonomic rank is only meaningful as part of a sequence, both treatments are technically correct. Ultimately, the issue hinges upon the Austro-American side neck turtles. These Pleurodira are less closely related to the Podocnemididae and Pelomedusidae than these are to each other. If all three are ranked as full families, the Chelidae is treated as a basal lineage, while the other two are united in the superfamily Pelomedusoidea. This treatment is preferred here, because it allows more convenient placement of prehistoric pleurodires.