It is known only from a few specimens including the type series, all from the pet trade supposedly from Guangxi or Vietnam. Either found in the wild or bred for the pet trade, it was later determined to be the offspring of a male Chinese Stripe-necked Turtle and a female Vietnamese Pond Turtle (Spinks et al. (2004), Stuart & Parham (2006)). If it is a wild-born hybrid, the specimen thus must have originated in central Vietnam, the only area where Mauremys annamensis / the Vietnamese Pond Turtle is known to exist and overlaps with the range of Ocadia sinensis
Buskirk, James R.; Parham, James F. & Feldman, Chris R. (2005): On the hybridisation between two distantly related Asian turtles (Testudines: Sacalia × Mauremys). Salamandra41: 21-26. PDF fulltext
Parham, James Ford; Simison, W. Brian; Kozak, Kenneth H.; Feldman, Chris R. & Shi, Haitao (2001): New Chinese turtles: endangered or invalid? A reassessment of two species using mitochondrial DNA, allozyme electrophoresis and known-locality specimens. Animal Conservation4(4): 357–367. HTML abstract Erratum: Animal Conservation5(1): 86 HTML abstract