You may Special Summon a high-level monster with “Pyramid Turtle”’s effect (like “Vampire Lord” or “Ryu Kokki”), but not a Special-Summon only monster (like “Spirit of the Pharaoh”).
Netrep Q&As:
Q: If a player activates “Creature Swap”, gives their opponent “Pyramid Turtle”, and then destroys the “Pyramid Turtle” in battle, will the player be able to attack with the Special Summoned monster from “Pyramid Turtle’s” effect?
A: Yes, in the situation presented the Zombie-Type monster Special Summoned by the effect of “Pyramid Turtle” may attack during that same Battle Phase. Curtis Schultz, 02/15/2004
GoatRulings.com Rulings:
Q: If “Newdoria” and “Pyramid Turtle” crash or destroy each other in battle can “Newdoria” destroy the monster summoned off of “Pyramid Turtle”?
A: No. “Newdoria” is a mandatory effect and “Pyramid Turtle” is an optional effect so “Newdoria” will be chain link 1 regardless of who turn player is. Newdoria must target at activation. So the target to be destroyed “Newdoria” will need to be chosen before the effect of pyramid turtle activates.