Key to the Butterfly Rays of the G. micrura Species Complex

1a. Dorsal cranial fontanelle keyhole-shaped; mesopterygium divided into two solid elements......... Gymnura sereti, sp. nov.

1b. Dorsal cranial fontanelle U shaped; mesopterygium divided into one anterior solid element and 5–7 smaller fragments.... 2

2a. Dorsal surface usually uniformly brown or gray, without any vermiculate pattern; number of total pectoral radials ranging from 112 to 119............................................................................. Gymnura micrura

2b. Dorsal surface brownish with a lighter vermiculate background; number of total pectoral radials ranging from 118 to 127..................................................................................... Gymnura lessae, sp. nov.