Video Library

Crinoids: Dr Charles Messing, Professor at Nova Southeastern University Oceanographic Center takes us on an exploration inside the deep sea for a look at Crinoids

Brisingids: Video published Jun 23, 2010. Copyright: S.W. Ross et al, UNC-W, NOAA-OCE (2005).

The Azoic hypothesis: Audio encyclopedia explanation of Forbes Theory.

Encyclopedia

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Crinoids are marine animals that make up the class Crinoidea of the echinoderms (phylum Echinodermata). The name comes from the Greek word krinon, "a lily", and eidos, "form".They live in both shallow water and in depths as great as 9,000 meters (30,000 ft). Those crinoids which in their adult form are attached to the sea bottom by a stalk are commonly called sea lilies. The unstalked forms are called feather stars or comatulids.

Crinoids are characterised by a mouth on the top surface that is surrounded by feeding arms. They have a U-shaped gut, and their anus is located next to the mouth. Although the basic echinoderm pattern of fivefold symmetry can be recognised, most crinoids have many more than five arms. Crinoids usually have a stem used to attach themselves to a substrate, but many live attached only as juveniles and become free-swimming as adults.

There are only about 600 extant crinoid species, but they were much more abundant and diverse in the past. Some thick limestone beds dating to the mid- to late-Paleozoic are almost entirely made up of disarticulated crinoid fragments.

The Brisingids are deep-sea-dwelling starfish in the order Brisingida

These starfish have between six and 18 long, attenuated arms which they use for suspension feeding. Other characteristics include a single series of marginals, a fused ring of disc plates, the lack of actinal plates, a spool-like ambulacral column, reduced abactinal plates, and crossed pedicellariae.

The Azoic hypothesis The theory was based upon Forbes' findings aboard the HMS Beacon, a surveying ship to which he had been appointed naturalist by the ship's commander Captain Thomas Graves. With Forbes aboard, the HMS Beacon set sail around the Aegean Sea on 17 April 1841, from Malta. It was at this point that Forbes began to take dredging samples at various depths of the ocean, he observed that samples from greater depths displayed a narrower diversity of creatures which were generally smaller in size.

Forbes reported his findings from the Aegean Sea in his 1843 report to the British Association entitled Report on the Mollusca and Radiata of the Aegean Sea. His findings were widely accepted by the scientific community and were bolstered by other scientific figures of the time. David Page (1814-1879), a respected geologist, confounded the theory by stating that "according to experiment, water at the depth of 1000 feet is compressed 1/340th of its own bulk; and at this rate of compression we know that at great depths animal and vegetable life as known to us cannot possibly exist – the extreme depressions of seas being thus, like the extreme elevations of the land, barren and lifeless solitudes."