An overview of polyplacophora and cephalopoda

Today, the only living representatives of shelled cephalopods are a few species of Nautilus.


The long separation of the two lineages has, today, resulted in lineages with cephalopods that are very different in structure. The following diagram shows the major classes, which as can be seen are all based on variation in this same body plan.

While this page field guide is tailored for Tasmania, it also covers most species you would find along the Australia, SAn coast.

Tusk shell

Cowries are the most loved and most collected of all seashell families and this book provides an excellent overview of the variety of species available worldwide. This secretes a dark fluid, the sepia or ink, which is forcibly ejected through the funnel.

That means that the eyes of squids and sepioids cuttlefish, etc.


The convex side has to be divided into anteriorly ventral and dorsally posterior portions, with the anus as the demarcation. The mantle of a scaphopod is entirely within the shell.

Cephalopods first appeared about million years ago in the Upper Cambrian Period. Consequently, the concave side of the shell and viscera are anatomically dorsal. Specifically, the Dentaliids are the physically larger of the two families, and possess a shell that tapers uniformly from anterior widest to posterior narrowest ; they also have a foot which consists of one central and two lateral lobes and which bends into the shell when retracted.

Both cuttlefishes and octopuses may use the tips of their arms as wormlike lures to attract small fishes, and octopuses have been reported to thrust stones between the valves of clams to prevent their closing.

References and resources Daniel, T. Cephalopod Hox genes and the origin of morphological novelties. The implications of these shapes on the animals' behavior and lifestyle could be profound, but how could it be tested. Studies have shown that in Octopus joubini raised from the egg in aquariums, sexual maturity and spawning were reached in five months; in a loliginid squid Sepioteuthis sepioidealikewise raised from the egg, sexual maturity and full growth were also attained in five months.

The pages also include Bivalves 18 familiesincl. The chambered nautilus Nautilus is a less active swimmer, partly due to the inefficient funnel, which is composed of two flaps instead of a single fused tube, and to a reduced mantle cavity. Most cephalopods possess colour pigment cells chromatophores and reflecting cells iridocytes in the skin.

Representing a new take on how best to assist collectors with often difficult identification of the diverse Conidae species, both books will be a most welcome addition to all general seashell libraries. Though nautiloids and ammonoids may appear the same, they are easily distinguished by the location of their siphuncle and the shapes of their sutures.

Arms and tentacles are another distinguishing cephalopod characteristic. The text includes an introduction to Oliva and detailed info on systematics. A separate set of pedal ganglia lie in the foot, and a pair of visceral ganglia are set further back in the body, and connect to pavilion ganglia via long connectives.


Roper, a similar situation exists in the deep-sea squid Bathyteuthis. The three authors have outlined the criteria for each genus with a detailed list of the species for each. Discussing modern taxonomy along with synonyms, historical and fossil records, the bookset provides much-needed insight and updates to current Cowrie systematics.

The sense organs of the cephalopods are eyesrhinophores olfactory organsstatocysts organs of equilibriumand tactile organs. The fossil record of most cephalopods in the clade Coloidea squid, cuttlefish, octopuses, and their relatives is poor, especially when compared to their shelly relatives.

During the Middle Ages, their coiled shells were interpreted by the English, who encountered them in Jurassic-aged rocks exposed throughout Great Britain, as lithified snakes called "snake stones". The team of authors also including Kurt Kreipl and David Monsecour comprehensively reviewed the family from a conchological perspective with a user-friendly layout to create a most helpful reference book for collectors and scientists alike.

Of the cuttlefishes, the Sepiidae are littoral, whereas the Sepiolidae dwell on or near the bottom, down to considerable depths. The hectocotylized arm of Octopus bears a deep groove on one side, ending in a spoonlike terminal organ.


Mollusca Overview. Bilateral symmetry, protostomy Trochophore larvae, COELOM REDUCED, circulatory system, mantle, radula What kind of reproduction does Cephalopoda have?

(Squid_ Chitons (look like trilobite) How many dorsal valves does the trilobite polyplacophora have? 8 dorsal valves. What kind of head does a polyplacophora have.

List of mollusc orders

The name Mollusca (from the Latin mollis "soft"), was first used by the great French zoologist Cuvier in to refer to cephalopods like squids and cuttlefish.

It was later extended to include other organisms of this group, such as snails and bivalves. A cephalopod (/ ˈ s ɛ f ə l ə p ɒ d, ˈ k ɛ f-/) is any member of the molluscan class Cephalopoda (Greek plural κεφαλόποδα, kephalópoda; "head-feet") such as a squid, octopus or exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles (muscular hydrostats) modified from the primitive molluscan foot.

Volborthella, some fossils of which predate, was long thought to be a cephalopod, but discoveries of more detailed fossils showed its shell was not secreted, but built from grains of the mineral silicon dioxide (silica), and it was not divided into a series of compartments by septa as those of fossil shelled cephalopods and the living Nautilus are.

Mollusca: General Characteristics! Gastropoda 40, sp Bivalvia 7, sp Other 5 Classes ~ Polyplacophora Cephalopoda Molluscan Taxonomic Classes Gastropoda Scaphopoda Bivalvia and Aplacophora Monoplacophora Cretaceous Triassic Polyplacophora Rostriconchians Gastropoda Bivalvia Cephalopoda.

Clams, snails, slugs, oysters, squid, octopus, chitins, and so much more! Characteristics of Molluscaspecies! Most marine; some fresh water; some terrestrial triploblastic coelomates Most with bilateral symmetry a water-filled mantle cavity a rasplike radula Muscular foot the muscular foot can be modified depending on the class of mollusks.

An overview of polyplacophora and cephalopoda
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