Evolution
Living fossils and the Permo-Triassic extinction
Stalked crinoids were first described as fossils and were thought to be long extinct until they were dredged from the Caribbean in the early 19th century. This caused something of a stir and they are still commonly known as living fossils.
Crinoids were at their most abundant during the Carboniferous but were severely reduced at the Permo-Triassic extinction event with only 1 linage surviving. All modern crinoids radiated from this single lineage.
Neocrinus and its relatives
Neocrinus:
- is closely related to other stalked crinoids such as Metacrinus, although its divergence from the other stalked crinoids is unknown.
- belongs to the family Isocrinidae which has a long fossil history stretching back to the Triassic when it appeared after the mass extinction at the end of the Permian.
Fossil remains of Neocrinus suggest it has been present in the Caribbean since the Miocene and has therefore undergone very little change for the past 20 million years or so (Donovan and Veltkamp, 2001).