Characteristic         

S. crassicollis is a largely aquatic turtle. It has a low, black upper shell (carapace) that is strongly serrated on the back edge. The shell on the underside of the turtle (plastron) is uniformly black or dark brown to yellowish-brown with dark blotches or patterns. The large and rather broad head is black to dark grey with a faded white, cream or yellow spot behind each eye. The snout is short and slightly projecting and the jaws are cream to tan in colour. The upper jaw bends upwards on both sides, giving this turtle a ‘smiling’ appearance. The limbs, tail and thick neck are dark grey to black. The front surface of each limb is covered with large scales. Male black marsh turtles have a slightly concave plastron and thicker, longer tails than the females, which have flat plastrons. The light head spots also often fade out in males, but are retained in females .