The Solothy is a Maxis-made creature, present in the final game. It is one of the creatures that appears on the Spore cover.
Solothies are carnivores, but they aren't very adept at killing prey. Their only attack is a very weak bite. They are better at socializing, however. They aren't very good singers, but are fine dancers and somewhat charming creatures. Their hands however don't have any special abilities, like posing or striking.
Solothy is on the Spore box cover. In the game, Solothy has a reptilian carnivore mouth, and there are no detail parts on its body. However, on the cover, Solothy has a swine herbivore mouth, and its body is covered in "heycorns". These were probably mistakes by Maxis.
In The Sims 3 and The Sims 4, one of the paintings a Sim can paint is a picture of a Solothy in Test Drive mode.