Prothamnodes platycycla is a moth in the Xyloryctidae family. It was described by Meyrick in 1923. It is known from Myanmar. The wingspan is about 23 mm. The forewings are light greyish-ochreous, the costal edge ochreous-whitish except towards the base. The stigmata are small and dark grey, the plical very obliquely beyond the first discal. There is a curved subterminal line of irregular blackish-grey dots and a terminal series of small indistinct dark grey dots. The hindwings are whitish-grey, somewhat darker posteriorly, the apical edge marked with dark grey suffusion and with a small cloudy dark grey spot on the costa beyond the middle.