The hard structure of the animal is composed of plates of crystalline calcium carbonate. Crinoids first appeared in Early Ordovician rocks. Although crinoids still exist today, the species found in ...

The fossil content of local limestone shows the diversity of life in the late Ordovician period. Bryozoans and brachiopods, nearly equal in abundance, form about 60% of the allochems in local ...

Learn more about the time period that took place 488 to 443 million years ago. 3 min read During the Ordovician period, part of the Paleozoic era, a rich variety of marine life flourished in the ...

There are around 800 extant species and the group has a long and detailed fossil record stretching back about 450 million years ago to the Late Ordovician Period ... the others being holothurians, ...

There are around 800 extant species and the group has a long and detailed fossil record stretching back about 450 million years ago to the Late Ordovician Period ... the others being holothurians, ...