Atelopus coynei is a relatively small harlequin frog, with females growing up to a length of 32 mm and males to 23 mm. The snout of A. coynei projects beyond the lower jaw, creating a sharp ninety-degree angle above the nostril when viewed in lateral profile. Atelopus coynei has a body wider than the head, its head is longer than wide. The laterally open nostrils are located along the line between the anterior margin of orbit to tip of snout, approximately a third of the distance from the snout. Viewed from above, the corner of the eyelids diverge from a point behind the nostrils to immediately anterior of the orbits after which they diverge more strongly. The canthus rostralis is roundish, with a subtle depression at the loreal region. The interorbital space in A. coynei is broader than the upper eyelid and the tympanum is obscured. The skin on A. coynei's head is smooth but can have sparse, fine granulations. The skin of the dorsum is granulated and exhibits twin ridges near the parotoid area. A. coynei has no dorsolateral folds, however, the venter and sides exhibit plate-like folds, with small, highly distinct folds at the neck and throat becoming less distinct and larger as they progress toward the cloaca. The forearms of this species are thick. The first finger digit is virtually entombed in fleshy, thick webbing. The other finger digits are webbed basally with lateral fringing. Hindlimbs of A. coynei are long, with heels that overlap slightly when the tibiofibulaes are held away from the body at a 90-degree angle. The hind feet are fleshy with heavy webbing that reaches the tips of all but the fourth toe (Miyata 1980).
Atelopus coynei can be differentiated from other similar species by its ventral patterning, thick fleshy finger webbing that covers its first finger, and from its long hind limbs that cause its heels to overlap when the legs are positioned perpendicular to the body (Miyata 1980).
In life, the male dorsum colors vary from green backgrounds with dark brown vein-like spotting to dark brown with green blotching. In all specimens, as the green color moves to the sides of the frog it becomes more turquoise blue. The ventral surface of males has an opaque white or yellow background that is decorated with a sparse black or brown network of color. The single female paratype had a venter that was bright, opaque yellow with dark brown reticulations. Both sexes had reddish-orange palms and soles, but with more prominent coloring on the females. Irises in both sexes were golden yellow to orange-copper. When preserved, green parts of the A. coynei turned pale lavender. Additionally, brown spots faded and obtain a reddish wash. In males, the venter white-belled variations were unchanged while yellow-belly colorations were lost. In the female, the venter retained its yellowish tint and the brown reticulations paled to a medium brown color (Miyata 1980).
Atelopus coynei was named after biologist Jerry Coyne, an evolutionary biologist, who helped collect a paratype in 1976 and provided financial support for Ken Miyata to the describe the species (Miyata 1980).
The type locality of A. coynei was lost to logging that caused sedimentation to the stream at which the holotype and paratypes were found (Miyata 1980).
Biodiversity within the range of A. coynei is very high, with an exceptional level of endemism as well. Notable mammals present here are the Spectacled Bear (Tremarctos ornatus), Jaguar (Panthera onca) and Andean Tapir (Tapirus pinchaque). Example avian species occurring in this ecoregion are the endemic Booted Racket-tail (Ocreatus underwoodii), Empress Brilliant (Heliodoxa imperatrix), the Fulvus Treerunner (Margaromis stellatus), the Black Solitaire (Entomodestes corocinus) and the Gorgeted Sunangel (Heliangelus strophianus).
There are an extraordinary number of amphibian taxa within the same ecoregion inhabited by A. coynei. Example associate endemic amphibians that overlap (or nearly overlap) the range of A. coynei are the Burrowe's Robber Frog (Pristimantis laticlavius), Duellman's Robber Frog (Pristimantis duellmani) and the Pirri Range Stubfoot Toad (Atelopus glyphus). Example reptilian endemics that overlap (or nearly overlap) the range of Atelopus coynei are: Antioquia Anole (Anolis antioquia) and the Saphenophis Snake (Saphenophis sneiderni).
Phylogeny and evolution:
All ancestral stock of genus Atelopus was likely present in South America prior to the Tertiary. Species within the genus Atelopus likely were adapted to stream-side habitats prior to the Andean uplift in the Cretaceous and Early Tertiary. As Andean uplift occurred, creating montane habitat, it lifted the species and corresponding speciation resulted for the medium to higher altitude species members including A. coynei; this higher altitude adaptation likely reflected the floral palette and microclimate (McDiarmid 1971).