The Saurexian rock-toad is descended from common toads from Earth, that were on board the colony ship that crashed on New Albuquerque.  Over the years, these toads evolved to survive the conditions of their new home. 

One of these adaptations caused their cells to produce a chemical commonly used by the Holy Empire of Man in their nano-weapons.  As a result, refugees from the Planetary League, fleeing the Great Reckoning, who had been inoculated with defensive nanotechnology, and came into direct contact with these toads were treated to a bizarre sight.  The defensive nanobots would disintegrate Saurexian rock-toads in a spectacular fashion.

See:  Tail of the Toad God