Red-necked pond turtle

The red-necked pond turtle ("Mauremys nigricans") is a species of turtles in the family Geoemydidae endemic to China. It is most likely restricted to Guangxi and Guangdong provinces, although pre-historic skull remains have been found in northern Vietnam and Hainan. Other common names include Kwangtung river turtle and black-necked pond turtle.
Anatomy and morphology.
A megacephalic form of the red-necked pond turtle exists, commonly called 'dumb-head'. This form is rarer than the smaller headed individuals. This species has strong sexual dimorphism with a significant size difference between males and females. The largest recorded male's carapace measured 185mm (7.2 in) in length whereas females with a size up to 298 mm (11.7 in) have been found.