Nilssonia is a genus of softshell turtles (family Trionychidae) from rivers, streams, ponds and lakes in South Asia and Burma. 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.
^ abGray, John Edward. 1872. Notes on the mud-tortoises of India (Trionyx, Geoffroy). Annals and Magazine of Natural History (4)10:326–340.
^Gray, John Edward. 1873. Notes on mud-tortoises (Trionyx, Geoffroy), and on the skulls of the different kinds. Proceedings of the Zoological Society of London 1873:38–72.
^Hay, Oliver P. 1904. On the existing genera of the Trionychidae. Proceedings of the American Philosophical Society 42:268–274.
^ abTurtle Taxonomy Working Group [van Dijk, P.P., Iverson, J.B., Rhodin, A.G.J., Shaffer, H.B., and Bour, R.]. 2014. Turtles of the world, 7th edition: annotated checklist of taxonomy, synonymy, distribution with maps, and conservation status. In: Rhodin, A.G.J., Pritchard, P.C.H., van Dijk, P.P., Saumure, R.A., Buhlmann, K.A., Iverson, J.B., and Mittermeier, R.A. (Eds.). Conservation Biology of Freshwater Turtles and Tortoises: A Compilation Project of the IUCN/SSC Tortoise and Freshwater Turtle Specialist Group. Chelonian Research Monographs 5(7):000.329–479, doi:10.3854/ crm.5.000.checklist.v7.2014.
^ abPraschag, 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. Scripta36(4): 301–310. doi:10.1111/j.1463-6409.2007.00282.x (HTML abstract)