What are the characteristics of malacostraca?

Distinguishing characteristics The head has 6 segments. Possess antennules, antennae and mouth parts. Usually have 8 pairs of thoracic legs and 8 thoracic segments. Possess compound stalked or sessile eyes.

Where are malacostraca found?

Most malacostracans live in the marine environments,but a few are found in the freshwater and terrestrial environments. They occupy all three dimensions in the water column, such as crawling on top of the sediment, burrowing in the substrate, or swimming with the oceans currents.

When did malacostraca first appear?

385 million to 359 million years ago
The first eucaridan malacostracans appear as fossils from the middle Paleozoic (Late Devonian Epoch, 385 million to 359 million years ago). These were burrowing, lobsterlike, protoglyphaeids with primitive, somewhat pincerlike walking legs and a tail fan with uropods.

What does a segmented body help malacostraca do?

The appendages of the last segment are typically flattened into uropods, which together with the terminal telson, make up the “tail fan”. It is the sudden flexion of this tail fan that provides the thrust for the rapid escape response of these crustaceans and the tail fan is also used in steering.

What do all Malacostraca have in common?

Common features of this class are three body regions: the head (five segments), thorax (eight segments), and abdomen (six to seven segments), each with jointed appendages, including two pairs of antennae on the head. Sometimes the head and thorax are fused into a cephalothorax, as in crayfish and crabs.

How many species are in Malacostraca?

The class Malacostraca contains more than 29,000 living species and represents about half of all known crustacean species. It is the single largest group not only of marine arthropods but also of all fully aquatic arthropod taxa.

What is the meaning of Malacostraca?

Definition of Malacostraca : a major subclass of Crustacea including most of the well-known marine, freshwater, and terrestrial members of the group (as lobsters, crabs, shrimps, sow bugs, beach fleas)

Which of the animals are included in class Malacostraca?

Malacostraca is the largest of the six classes of crustaceans, containing about 40,000 living species, divided among 16 orders. Its members display a great diversity of body forms and include crabs, lobsters, crayfish, shrimp, krill, woodlice, amphipods, mantis shrimp and many other, less familiar animals.

What are the five groups of Malacostraca?

Lobsters, crabs, hermit crabs, shrimp, and isopods are all malacostracan crustaceans.

How many species of malacostraca are there?

Malacostracans are distributed worldwide in marine, freshwater, and terrestrial environments. There are roughly 25,000 species in as many as fifteen orders. Decapoda (crabs, lobsters, and shrimps) is the most speciose group within the Malacostraca.

What order is Malacostraca?

Order Decapoda
Classification, Morphology, and Growth. Crayfish, crabs, and shrimp are members of the Phylum Arthropoda, Subphylum Crustacea, Class Malacostraca, and Order Decapoda.

What is the fossil record of Malacostraca?

The fossil record of the Malacostraca extends from the early Paleozoic Era (Early Ordovician Epoch, 488 million to 472 million years ago) to the present. The early phyllocarids (order Archaeostraca) had a body form which resembled the aquatic branchiocarid arthropods that were diverse in Cambrian seas, 542 million to 488 million years ago.

What is the classification of Malacostraca?

Malacostracan, any member of the more than 29,000 species of the class Malacostraca (subphylum Crustacea, phylum Arthropoda), a widely distributed group of marine, freshwater, and terrestrial invertebrates.

How did malacostracans evolve in the Paleozoic?

During the late Paleozoic (early Carboniferous through Permian Period, 359 million to 251 million years ago) malacostracans evolved rapidly, apparently in step with the proliferation of coastal vascular plants that formed a major new aquatic food resource.

What is the most primitive malacostracan?

Leptostracans are thought to be the most primitive of the malacostracans and date back to the Cambrian period. They range in length from 1 to 4 cm (0.4 to 1.6 in), most being suspension feeders though some are carnivores or scavengers.