Rhea (bird) to be growing. The genus name was given in 1752 by Paul Möhring and adopted as the English common name. Möhring named the rhea based on the Greek Titan Rhea, whose name is derived from the Greek "Rhea" () from έρα "ground". This was fitting with the rhea being a flightless ground bird. Depending on the South American region, the rhea is known locally as "ñandú guazu" (Guaraní, meaning big spider, most probably in relation to their habit of opening and lowering alternate wings when they run), "ema" (Portuguese), "suri" (Aymara and Quechua), or "choique" (Mapudungun). "Nandu" is the common
Flightless bird provided opportunities for Palaeognathes to distribute and occupy novel environments. New ecological influences selectively pressured different taxon to converge on flightless modes of existence by altering them morphologically and behaviorally. The successful acquisition and protection of a claimed territory selected for large size and cursoriality in Tertiary ancestors of ratites Temperate rainforests dried out throughout the Miocene and transformed into semiarid deserts causing habitats to be widely spread across the growingly disparate landmasses. Cursoriality was an economic means of traveling long distances to acquire food that was usually low lying vegetation, more easily accessed by walking Traces of these events