Information AboutPhragmocone |
| CATEGORIES ABOUT PHRAGMOCONE | |
| cephalopod zootomy | |
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The phragmocone is the chambered portion of the Shell of a Cephalopod . It is divided by Septa into Camerae . In most Nautiloid s and Ammonoid s, the phragmocone is a long, straight, curved, or coiled structure, in which the camarae are linked by a Siphuncle which determines Buoyancy by means of gas exchange. Despite this benefit, such a large shell adds to the weight of the animal, and hence is not advantageous in catching fast-moving prey. Some nautiloids, such as the Silurian Ascocerida , drop the phragmocone upon maturity, presumably to increase speed and maneuverability. They thus became the early Paleozoic equivalent of Coleoid s. The early coleoids and Belemnoid s adopted a different approach. The phragmocone is retained but became internal and reduced, and so like the shell in general it tends to be vestigial or absent in most cephalopods. |
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