Simplify the following text for a Grade 9 native English-speaking person.
Original: The fauna was dominated by tiered communities of suspension feeders , mainly with short food chains ; this said , the ecological system reached a new grade of complexity far beyond that of the Cambrian fauna , which has persisted until the present day .
Simplified: The fauna was dominated by suspension feeders , mainly with short food chains . The ecological system reached a new grade of complexity far beyond that of the Cambrian fauna .