Jenis Crinoid Feather Stars

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• Crinoidea comes from the Greek word krinon (a lily) and eidos (form) • Other Names: Sea lilies, feather starts. o Sea lilies refer to the crinoids in their adult forms, which are attached to the sea bottom by their stalks and resembling lilies. Feather stars refer to their unstalked forms. • There are two groups of living crinoids: o Those with columns, the living stalked crinoids. o Those without columns, the comatulids. • They come in an array of colors and the size of their living forms are few inches to a couple of feet in dimension o However, some extinct crinoids were great in size. One had a stalk of nearly 21.5 meters. length. • Their average lifespan is 15 years. • Their fossils have been used for jewelry. For example, Fossilised crinoid columnals extracted from limestone quarried on Lindisfarne (UK) or found washed up along the foreshore were threaded into necklaces or rosaries and became known as St. Cuthbert's beads.
Evolutionary Relationships Fossil Crinoid • Crinoids are the least understood of the living echinoderms, and their skeletal remains are one of the most abundant and important of fossils. • There are two competing hypotheses pertaining to the origin of the group: o The traditional viewpoint holds that crinoids evolved from within the blastozoans (the eocrinoids and their derived descendants the cystoids) where the most poplar alternative suggests that the crinoids split early from among edrioasteroid. o This debate is hard to settle because they all share many characteristics including radial symmetry, calcareous plates, and stalks or direct attachment to the substrate. • The earliest known group of crinoids date to the Ordovician period (roughly 490 million years ago) and underwent two major adaptive radiations during the Paleozoic Era (245-570 million years ago).
Page 1: Crinoid Feather Stars Scientific (G
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Page 10 and 11: Locomotion • Most crinoids are fr
Page 12 and 13: Reproduction and life cycle • The
Page 14: • Thy approximate 80 surviving sp

Jenis Crinoid Feather Stars

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