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However, most of other researchers do not agree that Nectocaris actually being a cephalopod or even mollusk. [140] [141] Early cephalopods were likely predators near the top of the food chain. [25] After the late Cambrian extinction led to the disappearance of many radiodonts, predatory niches became available for other animals. [142]
Only cephalopods with chambered shells have siphuncles, such as the extinct ammonites and belemnites, and the living nautiluses, cuttlefish, and Spirula. In the case of the cuttlefish, the siphuncle is indistinct and connects all the small chambers of that animal's highly modified shell; in the other cephalopods it is thread-like and passes ...
Edible molluscs are harvested from saltwater, freshwater, and the land, and include numerous members of the classes Gastropoda (snails), Bivalvia (clams, scallops, oysters etc.), Cephalopoda (octopus and squid), and Polyplacophora (chitons). Many species of molluscs are eaten worldwide, either cooked or raw.
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Synchrotron analysis of an aptychophoran ammonite revealed remains of isopod and mollusc larvae in its buccal cavity, indicating at least this kind of ammonite fed on plankton. [30] They may have avoided predation by squirting ink, much like modern cephalopods; ink is occasionally preserved in fossil specimens. [34]
It is not made of aragonite as most other shells are, but of calcite, with a three-layered structure [7] and a higher proportion of magnesium carbonate (7%) than other cephalopod shells. [ 8 ] The eggcase contains a bubble of air that the animal captures at the surface of the water and uses for buoyancy, similarly to other shelled cephalopods ...
Spirula spirula is a species of deep-water squid-like cephalopod mollusk. It is the only extant member of the genus Spirula , the family Spirulidae , and the order Spirulida . Because of the shape of its internal shell, it is commonly known as the ram's horn squid [ 3 ] or the little post horn squid .
In a broad sense, "nautiloid" refers to a major cephalopod subclass or collection of subclasses (Nautiloidea sensu lato). Nautiloids are typically considered one of three main groups of cephalopods, along with the extinct ammonoids (ammonites) and living coleoids (such as squid, octopus, and kin).