Simplify the following text for a Grade 10 native English-speaking person.
Original: Many trilobites developed bizarre spines and nodules to defend against predators such as primitive sharks and nautiloids while other trilobites such as Aeglina prisca evolved to become swimming forms .
Simplified: Many trilobites developed bizarre spines and nodules to defend against predators such as primitive sharks and nautiloids . Other trilobites evolved to become swimming forms .