What are the three classes of phylum Mollusca?
Mollusks are subdivided into seven classes with most species found in three of those classes: Gastropoda, Bivalvia, and Cephalopoda.
What are the Synapomorphies of Mollusca?
The mollusks are among the most diverse, and well-known of the invertebrate groups and include the clams, snails, tusk shells, chitons, and squids. Nielsen (2001) identifies 5 synapomorphies that define the phylum: the mantle, the foot, the radula, and pectinate gills.
What are the 4 main characteristics of mollusks?
Mollusca Characteristics
- They are mostly found in marine and freshwater.
- They exhibit organ system level of organization.
- Their body has a cavity.
- The body is divided into head, visceral mass, muscular foot and mantle.
- The head comprises of tentacles and compound eyes.
- The body is covered by a calcareous shell.
What fossils are in the Mollusca phylum?
Over 26,000 species have been identified. They are commonly called clams. Common fossilized genera include: Inoceramus, Myalina, Aviculopecten, Septimyalina, and Wilkingia.
Which of the animals is a mollusk?
Mollusca is one of the most diverse groups of animals on the planet, with at least 50,000 living species (and more likely around 200,000). It includes such familiar organisms as snails, octopuses, squid, clams, scallops, oysters, and chitons.
What common features do all mollusks have?
WHAT FEATURES DO MOLLUSKS HAVE IN COMMON? As well as a shell, most mollusks have a muscular foot for creeping or burrowing. Some also have a head with sense organs. The soft body includes lungs or gills for breathing, and digestive and reproductive parts, all enclosed by a skinlike organ called the mantle.
What is a mollusk fossil?
Although most molluscs live in the sea, some are land dwellers such as the snail and slug. Mollusc fossils are usually well preserved because of their hard shell. But those without a shell, such as the slug and octopus, are rarely found as fossils.
Where did molluscs evolve from?
However, the Helcionellids, which first appear over 540 million years ago in Early Cambrian rocks from Siberia and China, are thought to be early molluscs with rather snail-like shells. Shelled molluscs therefore predate the earliest trilobites.
What is an example of a mollusk?
GastropodsBivalviaCephalopodOctopusScallopsPacific geoduck
Mollusca/Lower classifications
What is considered a mollusk?
Molluscs are a clade of organisms that all have soft bodies which typically have a “head” and a “foot” region. Often their bodies are covered by a hard exoskeleton, as in the shells of snails and clams or the plates of chitons.
Are mollusks amphibians?
Mollusks are a phylum of invertebrate animals defined by their distinct body structure — a head, a visceral mass, a mantle and some kind of foot. The mantle protects the mollusk’s body in place of a skeletal structure, and the “foot” has taken on many adaptions across the mollusca species.
How do mollusks differ from other animals?
Although there is no single feature that all molluscs possess, three features are so common in molluscs that they are used to distinguish them from organisms in other phyla: All molluscs have a specialized foot used in digging, grasping, or creeping.
Where are molluscs fossils found?
Mollusk fossils representing all three of these classes are found in the Ordovician, Silurian, Devonian, Mississippian, and Pennsylvanian rocks of Kentucky.
What did molluscs evolve?
Fossil record However, the evolutionary history both of the emergence of molluscs from the ancestral group Lophotrochozoa, and of their diversification into the well-known living and fossil forms, is still vigorously debated.
What was the first mollusk?
Mollusks have been diverse and abundant animals since earliest Cambrian time (about 545 million years ago = mya), and predate the appearance of trilobites in the fossil record.