Usually the quadratojugal is present only as a short element attached to the quadrate, but in one specimen of P. spinipollex the quadratojugal articulates with the maxillary and forms a complete quadratojugal-maxillary arch on each side of the skull.
"A Review of the Middle American Tree Frogs of the Genus Ptychohyla"
William E. Duellman
Berry dry, quadrate, depressed, the shell hard, 4 grooves, 4 cells, each containing a seed.
"The Medicinal Plants of the Philippines"
T. H. Pardo de Tavera
Pistillate: Corolla diminutive, 5 toothlets; anther none; stigmas 2. Seeds of both small and quadrate, smaller in the latter.
"The Medicinal Plants of the Philippines"
T. H. Pardo de Tavera