Santa Cruz field station near Iquitos, Depto Loreto, Peru. January 20, 2011.
Because this species can be incredibly ornate, I include photos of two different frogs found on the same day (they can also be quite plain in appearance). This species can be confused with O. deridens and other species, so here are some of the characteristics that define O. planiceps: Dark spots against a white or cream colored flank (easiest diagnostic). Extremely flat head in comparison to other species. Pronounced canthus rostralis, darker loreal area. Iris is gold, with irregular radiating dark lines; lower iris is somewhat darker. Eye has a transverse dark band running through the pupil. Feet webbed to toe pads, hand webs small. Toe pads more round than oval. Dark tympanum, about 2/3 the size of the eye, and often surrounded by an equally dark blotch.. No noticeable tubercles or spines on dorsum. White upper lips, with darker lip line present. Dorsum usually with a marbled or banded appearance involving several shades of tans and browns.
My Flickr album for this species is here.