The Silverstone’s poison frog’s circular tympanum, or eardrum, is concealed post-dorsally and is greater than 50% of the eye.
The Silverstone’s poison frog’s tympanum, or eardrum, is concealed post-dorsally where it subcutaneously dips under the anterior edge of the m. depressor mandibulae.
The m. depressor mandibulae is comprised of three slips. A large, superficial slip originates from the dorsal fascia and conceals a deeper slip originating on the otic ramus of the squamosal bone. A shorter, poorly defined slip originates on the posterior part of the tympanic ring. There is no m. adductor mandibulae externus superficialis. Thus, in the aforesaid characters, the jaw musculature is of the normal dendrobatid pattern.
Generally in dendrobatids, the large superficial slip of the depressor mandibulae muscle tends to slightly overlap the tympanic ring and, in any case, holds the skin away from the rear part of the tympanum, thus accounting for the fact that the tympanum is only partially indicated externally.
The tympanum is seen by dissection to be circular or slightly vertically elliptical with an area greater than 50% of the eye.