A ship of the Grand Survey discovers the planet Ythri:
sun G9, half Solar luminosity;
Ythrian gravity 0.75 terrestrial;
thinner, drier but humanly breathable atmosphere;
red, moss-like ground cover;
two small moons;
woods, lakes, plains, mountains;
winged carnivores lifting bodies heavy enough for intelligence by pumping oxygen with adapted gills, each needing a large territory for hunting or herding meat animals.
There are more data about Ythrians in the post "Who Knows Of Avalon?" (April, 2012).