One of the most populous and overlooked animals in the ocean since at least the Ordovician is the group of over 500 extant species in the genus Articulata. Also known as Crinoids, these strange animals belong to the class Crinoidea, live in areas from the shallows to at least 9,000 m deep, and have a historical range in three additional genera (all extinct) that spans the globe leaving fossils in a large range of geographic areas and geological time zones. The fossils of these passive filter feeding animals have been found attached to fossilized driftwood, the bottoms of ancient oceans, and in lengths in excess of 40 m. As single stalked echinoderms that were enormously successful, Crinoids underwent two explosive radiations early in their evolution in both the Ordovician, when they first definitively appear in the fossil record, and during the very early Triassic, after an extinction event near the end of the Permian initially bottle-necked the Crinoid record for a short period. This second radiation lacked morphological diversity previously seen in Crinoids, but did exhibit some of the longest individuals with
Pentacrinites reaching lengths of approximately 40 m (130 ft).
Given that there are hundreds of species and somewhat fewer genera, the reason that Crinoids have been lumped together for this week is because the wealth of information for any one individual species is actually quite limited, online, and there are a number that are not even mentioned anywhere online aside from acknowledgement that they existed. Talking about the entire group together we can discuss a large number of morphologies all at once and compare them. Be prepared for a lot of talk about stalks and plant-like morphologies. These are very unique animals that are often mistaken for plants. Be amazed, or perhaps underwhelmed, by their looks!
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