Both are mainly green, with red or maroon markings on the forehead, forecrown, broad superciliary stripe, and feathers on the bend of the wing, the carpal edge and the thighs.

[3][4][5] The genus was described by French naturalist Charles Lucien Bonaparte; the name is derived from the Ancient Greek terms rhynchos "beak", and psitta "parrot".

[8] Possibly its bill was adapted to feeding on a species of pine which disappeared due to climate change at the end of the last ice age, driving it to extinction.

The populations of both species have declined primarily due to habitat degradation, and now both are restricted to a few small areas in the mountains of northern Mexico.

[11][13] An earlier attempt in the 1980s and 1990s to reintroduce thick-billed parrots to Arizona failed because the captive-bred birds had not learned to avoid their natural and human predators,[14] but new plans for the reintroduction of this species include the use of wild-caught individuals.