akdosom ("Graid")

Radiation? there is a fair amount more than average, but not really.

Giant predators? oh dear. there's a reason the graid became apex predators through might, instead of mind.

i'll just give a few highlights to illustrate my point. no, I wont describe what they look like (and any pictures on GS are no longer valid) thats for the wildlife section on the planet sheet, if we ever get one.

first, lets not forget the graid themselves. They have no social instinct until reaching sentience. that means they need to be able to withstand a lot of blunt trauma.

next I would bring up the Achara. not large, but travels in large pack. has wicked running speed, 20 inch long talons known to break through rock, and an intellegence greater than anything but the graid themselves. not the danger they used to be though, now that they have been 'civilized.'

The Yrasslr are the largest animals currently living on earthsky, roughly the size of three Apatosaurus.
there are currently 138 of them currently alive. These ancient roaming titans have names and stories associated with them, individualy (such as say Nyvrsing, eternal rime, Beast spirit of the north). oh and they they could totaly crush you with a flick of the wrist (they do not have wrists)

and finaly, if the Yrasslr are a force of nature, the Vrenjai is a legend. Graid naturalist can't explain how such a creature can exist, let alone fly, speculating it has some innate ability to sing to the winds. a mysterious and ancient power, The vrenjai has been confirmed to carry off Graid who spent a little to long in the open at high elevations.
as far as it is know, there is only one pair of Vrenjai on the planet.

how long have they been around? Very long.