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Cephalopods became dominant during the Ordovician period, represented by primitive nautiloids. The class now contains two, only distantly related, extant subclasses: Coleoidea, which includes octopuses, squid, and cuttlefish; and Nautiloidea, represented by Nautilus and Allonautilus. In the Coleoidea, the molluscan shell has been internalized ...
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 ).
The teleosts are divided into the major clades shown on the cladogram, [19] with dates, following Near et al. [15] More recent research divide the teleosts into two major groups: Eloposteoglossocephala (Elopomorpha + Osteoglossomorpha) and Clupeocephala (the rest of the teleosts). [20] [21]
Teleosteomorpha is a clade of ray-finned fishes containing all teleost fish and their closest extinct relatives. [1] Also in this group are two diverse Mesozoic fish orders, the Aspidorhynchiformes and the Pachycormiformes. [2]
Some shelled molluscs, such as scallops can briefly swim by clapping their two shells open and closed. The molluscs most evolved for swimming are the cephalopods. Violet sea-snails exploit a buoyant foam raft stabilized by amphiphilic mucins to float at the sea surface. [11] [12] Among the Deuterostomia, there are a number of swimmers as well.
This could represent the origin of the two derived groups. [41] Unlike most modern cephalopods, most ancient varieties had protective shells. These shells at first were conical but later developed into curved nautiloid shapes seen in modern nautilus species. It is thought that competitive pressure from fish forced the shelled forms into deeper ...
Teuthology (from Greek τεῦθος, "cuttlefish, squid", and -λογία, -logia) [1] is the study of cephalopods, which are members of the class Cephalopoda in the phylum Mollusca. Some common examples of cephalopods are octopus, squid, and cuttlefish. Teuthology is a large area of study that covers cephalopod life cycles, reproduction ...
Pain in cephalopods is a contentious issue. ... Extant cephalopods are divided into two subclasses, ... (teleosts) Molluscs (cephalopods) Crustaceans