Your use of the word "introduced" suggests that they were added to a specific habitat somewhere. The question cannot be answered without knowing which habitat they were supposed to be introduced to. Crinoids have been around for about 350 million years.
Penis
The Age of Crinoids
it occurs in the precambrian period.
The snail was introduced to earth in the Late Cambrien period.
the carboniferous period had crinoids,echinoderms but today we don't have it
Crinoids were marine animals with long, feathery arms that anchored themselves to the seafloor, while foraminifera were single-celled organisms that formed shells out of calcium carbonate. Both organisms were abundant during this period and played important ecological roles in marine ecosystems.
The scientific name for the Crinoids is (class)Crinoidea.
Ancient Greece
At the end of the Permian Period which was about 251 million years ago
From the 600s BCE.
Crinoids and ammonites were the dominant marine life forms during the Mississippian stage of the Carboniferous period.
to let people know if the time period was before or after Jesus Christ.