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Black-shouldered Treefrog Jan 2013; Madre Selva Biological Preserve, Rio Orosa, Dpto. Loreto, Peru.

Well, darn, I exclaimed. I know what this treefrog is. It’s one I’ve been looking for more than 15 years. It’s the Black-shouldered Treefrog, Trachycephalus (formerly Phrynohyas) coriacea!

My exclamation was so loud and unexpected that all other members of the herp photography tour stopped and looked curiously at me. Many were snake enthusiasts and could not really understand this excitement over a treefrog that was barely 1½” snout-vent length. But a few were amphibian enthusiasts and well understood my delight.

I had just sat looking at the frog’s rose colored sides and brown back for nearly a half an hour before the realization hit me. I had known I had seen the frog before but I simply couldn’t remember where or when -— warm brown dorsum, rose sides. Why did it look so familiar?

And then, just as I was about to release it into the forest, the frog turned its head slightly and in so doing lifted a heavy tympanal skin fold to reveal a large black spot shoulder spot it had been concealing.

After that recognition clicked. I had seen this pretty rainforest anuran in Rodriguez and Duellman’s 1994 publication Guide to the Frogs of the Iquitos Region, Amazonian Peru. I was very familiar with the other two species in this genus, but had neither seen nor heard of the T. coriacae prior to that publication. Nor in the ensuing 17 years had I again seen it either in photos or life until now. And just because those drooping tympanal folds had so effectively concealed the identifying black shoulder spots on this half grown treefrog, I had nearly bypassed an opportunity to make its acquaintance.