Nilssonia is a genus of softshell turtles (family Trionychidae). In many treatments, it is monotypic, with the single species Burmese Peacock Softshell (N. formosa). However, the supposed other genus of peacock softshells, Aspideretes, is even closer related to N. formosa than was previously believed. They differ only in the neural plates between the first pleural scale pair of the bony carapace, which are fused into one in N. formosa and unfused in the others.
Thus, it has been proposed to unite the two genera under the older name, Nilssonia. As it seems, the closest living relatives of the Burmese peacock softshell are the Ganges Soft-shelled Turtle (A./N. gangeticus) and the Nagpur Soft-shelled Turtle (A./N. leithii), making the merging of the genera well warranted.
If the genera are united there are five species:
- ^ a b Praschag et al. (2007)
- Praschag, P.; Hundsdörfer, A.K.; Reza, A.H.M.A. & Fritz, U. (2007): Genetic evidence for wild-living Aspideretes nigricans and a molecular phylogeny of South Asian softshell turtles (Reptilia: Trionychidae: Aspideretes, Nilssonia). Zool. Scripta 36(4): 301–310. doi:10.1111/j.1463-6409.2007.00282.x (HTML abstract)