Ammonoids are an extinct group of marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs are more closely related to living coleoids (i.e., octopuses, squid, and cuttlefish) than they are to shelled nautiloids such as the living Nautilus species.
Among the shell-less molluscs ("Aplacophora") there are about 340 of the most primordial molluscs to be found on earth. As their scientific name Aplacophora literally states, the members of this group actually are devoid of a shell and in that regard are unique among molluscs.
Like fish, bivalve mollusks breathe through their gills. As filter feeders, bivalves gather food through their gills. Some bivalves have a pointed, retractable "foot" that protrudes from the shell and digs into the surrounding sediment, effectively enabling the creature to move or burrow.
Cephalopods are the only mollusks with a closed circulatory system. Coleoids have two gill hearts (also known as branchial hearts) that move blood through the capillaries of the gills. A single systemic heart then pumps the oxygenated blood through the rest of the body.
The mollusks or molluscs are the large and diverse phylum Mollusca,which includes a variety of familiar creatures well-known for theirdecorative shells or as seafood. These ra … nge from tiny snails,clams, and abalone to the octopus, cuttlefish and squid (which areconsidered the most intelligent invertebrates).
The gastropods (/ ˈ ɡ æ s t r oʊ p ɒ d /), more commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca, called Gastropoda. This class includes snails and slugs of all species and sizes, from microscopic to Achatina achatina, the largest known land gastropod.
Molluscs are generally regarded members of the Lophotrochozoa, a group defined by having trochophore larvae and, in the case of living Lophophorata, a feeding structure called a lophophore. The other members of the Lophotrochozoa are the annelid worms and seven marine phyla.
Kimberella is a monospecific genus of bilaterian known only from rocks of the Ediacaran period. The slug-like organism fed by scratching the microbial surface on which it dwelt in a manner similar to the gastropods, although its affinity with this group is contentious.
Monoplacophora, meaning "bearing one plate", is a polyphyletic superclass of molluscs with a cap-like shell now living at the bottom of the deep sea. Extant representatives were not recognized as such until 1952; previously they were known only from the fossil record.
Scallops are in the phylum Mollusca, a group of animals that also includes snails, sea slugs, octopuses, squid, clams, mussels, and oysters. Scallops are one of a group of mollusks known as bivalves. These animals have two hinged shells that are formed of calcium carbonate.
They concluded that Wiwaxia was a member of a clade that includes molluscs. Scheltema has also highlighted similarities between Wiwaxia and the larvae of certain solenogaster molluscs, which bear iterated calcareous sclerites arranged into three symmetrical lateral zones.