This species inhabits mainly the fall lines of rivers in the Mobile Bay drainage, in Alabama and Mississippi.

[6] The carapace of G. nigrinoda is slightly domed with the first four vertebrae possessing backward-projecting, knob-like processes, which are black in color.

[5] Black-knobbed map turtles are seasonally active from April to late November.

[7][9] Thermoregulation is thought to be the reason for basking, along with the removal of parasites and algal growth.

[9] Upon examination of both female and male stomach matter, Lahanas[7] found a distinction of food material percentages.

[2] The black-knobbed map turtle is most likely threatened by habitat degradation and encroachment by humans.

Humans have been known to remove dead logs that line the shoreline of rivers, which the turtle uses for basking in the sun.

Additionally, the turtle population could decline due to the consumption of their eggs by humans or other predators.

[9] However, it remains unclear if captive-bred black-knobbed map turtles can be released into the wild and breed on their own.

Black-knobbed map turtles are popular in the pet trade, but became more common because of captive breeding.