What type of marine organisms became dominant during the Mississippian?

During the Mississippian Period (359 to 323 million years ago), corals and crinoids became dominant marine organisms.

Here's a breakdown:

* Corals: These colonial animals built vast, complex reefs, creating diverse ecosystems. The Mississippian saw the rise of rugose corals, which were common throughout the period.

* Crinoids: These filter-feeding echinoderms, resembling feathery plants, were also abundant. They formed large "crinoid meadows" on the seafloor.

Other important groups that flourished during the Mississippian:

* Brachiopods: These bivalve-like animals were still prevalent.

* Trilobites: While declining in diversity, they were still present in Mississippian seas.

* Fish: Bony fish, particularly sharks, became more diverse and abundant.

* Ammonoids: These cephalopods, characterized by their coiled shells, experienced significant diversification.

The Mississippian was a time of significant ecological change in the oceans, marked by the rise of these key groups and a decrease in others.