The 2015 study established seven distinguishing traits of the genus as such.
These were autapomorphies, unique derived characters.
On the back of the skull, the paroccipital process is curved in side view.
The teeth have paired wear facets.
The first neck vertebra, the atlas, has a neural spine with processes pointing to the front and the inside, which are separate from the rear wing of the spine.
This rear wing shows a continuous transverse width over most of its length.
The neural arch of the atlas has on each side of its base a small triangular spur.
The second neck vertebra, the axis, has a neural spine with a knob-shaped bump on the front end of the ridge on its front side.
With the middle and rear neck vertebrae, the ridge between the rear joint processes, the postzygapophyses, does not extend beyond the rear edge of the neural arch.

 
The study also determined six autapomorphies of the type species Galeamopus hayi alone.
The part of the parietal bone forming the edge between the rear skull and the skull roof is low, with a height less than that of the foramen magnum.
The appending basipterygoid processes at the underside of the braincase strongly diverge at an angle of more than 60°.
The ulna of the lower arm is long, with a minimum length equalling 76% of the humerus, upper arm bone, length.
The surface on the radius contacting the ulna is limited in size and relatively smooth.
The joint surface at the underside of the radius is bevelled relative to the shaft, at an angle of about 15°.
The outer edge of the top surface of the shinbone forms a pinched process, behind the cnemial crest at the front.

 
Combined, there are thirteen autapomorphies present in Galeamopus, exactly the minimum the study used as a criterion to distinguish separate genera.
The 2015 study established seven distinguishing traits of the genus as such. These were autapomorphies, unique derived characters. On the back of the skull, the paroccipital process is curved in side view. The teeth have paired wear facets. The first neck vertebra, the atlas, has a neural spine with processes pointing to the front and the inside, which are separate from the rear wing of the spine. This rear wing shows a continuous transverse width over most of its length. The neural arch of the atlas has on each side of its base a small triangular spur. The second neck vertebra, the axis, has a neural spine with a knob-shaped bump on the front end of the ridge on its front side. With the middle and rear neck vertebrae, the ridge between the rear joint processes, the postzygapophyses, does not extend beyond the rear edge of the neural arch.
 
The study also determined six autapomorphies of the type species Galeamopus hayi alone. The part of the parietal bone forming the edge between the rear skull and the skull roof is low, with a height less than that of the foramen magnum. The appending basipterygoid processes at the underside of the braincase strongly diverge at an angle of more than 60°. The ulna of the lower arm is long, with a minimum length equalling 76% of the humerus, upper arm bone, length. The surface on the radius contacting the ulna is limited in size and relatively smooth. The joint surface at the underside of the radius is bevelled relative to the shaft, at an angle of about 15°. The outer edge of the top surface of the shinbone forms a pinched process, behind the cnemial crest at the front.
 
Combined, there are thirteen autapomorphies present in Galeamopus, exactly the minimum the study used as a criterion to distinguish separate genera.
Galeamopus