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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]
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).
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.
Fossilised Orthoceras orthocones.. An orthocone is the long, cone-shaped shell belonging to several species of ancient nautiloid cephalopod—the prehistoric ancestors of today's marine cephalopod mollusks, including the cuttlefishes, nautiluses, octopuses and squids. [1]
Cephalopod limbs bear numerous suckers along their ventral surface as in octopus, squid and cuttlefish arms and in clusters at the ends of the tentacles (if present), as in squid and cuttlefish. [9] Each sucker is usually circular and bowl-like and has two distinct parts: an outer shallow cavity called an infundibulum and a central hollow ...
Neocoleoidea (most living cephalopods) Coleoidea [ 1 ] [ 2 ] or Dibranchiata is one of the two subclasses of cephalopods containing all the various taxa popularly thought of as "soft-bodied" or "shell-less" (i.e. octopus , squid and cuttlefish ).
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 .
An ink sac is an anatomical feature that is found in many cephalopod mollusks used to produce the defensive cephalopod ink. With the exception of nocturnal and very deep water cephalopods , all Coleoidea (squid, octopus and cuttlefish) which dwell in light conditions have an ink sac, which can be used to expel a cloud of dark ink in order to ...