Fantastic Fossils by Donald R. Prothero

Author:Donald R. Prothero
Language: eng
Format: epub
Tags: NAT015000, Nature/Fossils, SCI054000, Science/Paleontology
Publisher: Columbia University Press
Published: 2020-03-30T16:00:00+00:00

Figure 16.11 ▲

The intersection of the edge of the septum with the outer shell forms a line called the suture, which can be seen in fossils if the outermost shell layers are scraped or eroded away. The details of the patterns of saddles and lobes in the suture enable paleontologists to identify almost any ammonoid. (Redrawn from several sources by Mary Persis Williams)

The rest of the body of the nautilus resembles the unshelled squid and octopus in shape. The large head is covered with a hood, and big eyes dominate body. Nautilus has a parrot-like beak in the mouth, surrounded by a ring of tentacles, which it uses to catch prey (mostly crustaceans and carrion). Beneath the head is the mantle cavity, where the gills lie. At the entrance to the mantle cavity is a nozzle called the hyponome, which funnels and focuses the jet of water to propel them. As the body squeezes down on the mantle cavity, it forces the water out the hyponome and creates a jet of water. Like octopus, however, nautilus uses jet propulsion only for rapid motion, especially when escaping. Most of the time, they use their tentacles to creep along the seafloor in any direction, especially when they are hunting.

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