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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]
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 ...
Other mollusks include gastropods, scaphopods and bivalves. Traditionally, the most common classification of the cephalopods has been a four-fold division (by Bather, 1888), into the orthoceratoids, nautiloids, ammonoids, and coleoids. This article is about nautiloids in that broad sense, sometimes called Nautiloidea sensu lato.
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.
Cuttlefish, like other cephalopods, have sophisticated eyes. The organogenesis and the final structure of the cephalopod eye fundamentally differ from those of vertebrates, such as humans. [20] Superficial similarities between cephalopod and vertebrate eyes are thought to be examples of convergent evolution. The cuttlefish pupil is a smoothly ...
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.
Marine gastropods mating. The reproductive system of marine gastropods such as those from class Opisthobranchia and order Archaeogastropoda from the class Prosobranchia, is a continuous cycle of alternating male and female reproductive role prevalence.
Teichert C, 1988, Main Features of Cephalopod Evolution, Ch 2 in The Mollusca Vol 12 Paleontology and Neontology of Cephalopods, Clarke & Trueman (eds) Academic Press. Wade, M 1988. Nautiloids and their descendants: cephalopod classification in 1986; New Mexico Bureau of Mines & Mineral Resources Memoir 44, Oct 1988 :15-25.