this is interesting - for future reference:
G. parnaibae - dorsal: 17 spines, 10 rays; anal: 7 rays; 31 E1 scales
G. camopiensis - dorsal: 16 spines, 11 rays; anal: 7 rays; 31 E1 scales
G. abalios - dorsal: 18 spines, 11 rays; anal: 8 rays; 34 E1 scales
G. altifrons - dorsal: 18 spines, 11 rays; anal: 8 rays; 37 E1 scales
G. brachybranchus - dorsal: 17 spines, 12 rays; anal: 8 rays; 33 E1 scales
G. brokopondo - dorsal: 17 spines, 12 rays; anal: 8 rays; 33 E1 scales
G. dicrozoster - dorsal: 17 spines, 12 rays; anal: 8 rays; 36 E1 scales
G. megasema - dorsal: 17 spines, 12 rays; anal: 8 rays; 37 E1 scales
G. proximus - dorsal: 17 spines, 12 rays; anal: 8 rays; 33 E1 scales
G. surinamensis - dorsal: 17 spines, 12 rays; anal: 8 rays; 33 E1 scales
G. winemilleri - dorsal: 19 spines, 12 rays; anal: 8 rays; 35 E1 scales
source -
http://www.practicalfishkeeping.co.uk/pfk/pages/item.php?news=1002