The Cogwheel Turtle is easy to recognize due to its distinctive shell, which is marked by spines on the keel and pleural scutes. The Cogwheel Turtle grows between 7 and 8.5 inches (18 and 22 cm) in length, and weighs between 3.3 and 4.5 pounds (1.5 and 2.0 kg) at maturity. They are named for their spikes, or spines though adult Cogwheel Turtles may loose their spines when they reach maturity. Young Cogwheel Turtles have been said to resemble pincushions because their spikes are so sharp. As they mature these will wear down and are not nearly as obvious as those of the young. Some adults may not have visible spikes, particularly those on the side. They can be difficult to sex. Males usually have longer, broader tails than the females. Males also have a concave plastron.