Simplify the following text for a Grade 12 native English-speaking person.
Original: Brachiopods , bryozoans and echinoderms were also heavily affected , and the endocerid cephalopods died out completely , except for possible rare Silurian forms .
Simplified: Brachiopods , bryozoans and echinoderms were also heavily affected , and the cone-shaped nautiloids died out completely , except for rare Silurian forms .