Classification of Arthropoda

Including some 19 classes,75 orders & 2400 families.

Major variation in the arthropods body plan have occurred mainly 2 directions,

1.Reduced the number of the body segment through the fusion, loss.

2.Reduced the number of locomotory appendages & specialize the remaining appendages for other functions.

Arthropods divide into 4 main subphyla.

1.Subphylum Trilobita.

2.Subphylum Chelicerata.

3.Subphylum Crustacea.

4.Subphylum Uniramia.

Subphylum Trilobota.

No living forms today.

These primitive arthropods displayed a high degree of segmentation and each segment carried a pair of appendages.

2 longitudinal furrows divided their body into 3 lobes.

Limbs are biramous.

Lacked head appendages.

Subphylum Chelicerata

They are mostly terrestrial forms.

They have 6 pairs of appendages.

That including a pair of chelicerae, pair of pedipalps, and 4 pairs of legs.

These are the only arthropods that lack antennae.

Their body consists of 2 tagmata.

This subphylum consists of three classes.

They are,

1.Class Merostomata.

2.Class Pycnogonida.

3.Class Arachnida.

Subphylum Crustacea

Major aquatic group of arthropods.

Appendages are biramous.

They have 2 pairs of antennae.

Also, possess a pair of mandibles & 2 pairs of maxillae.

The carapace covers all or part of the body.

Crustacea divide into some major classes.

They are,

1.Class Malacostraca

2.Class Cirripedia

3.Class Copepoda

4.Class Ostracoda

5.Class Branchiopoda

6.Class Branchiura.

Subphylum Uniramia

They evolved on land.

Their appendages are basically unbranched.

They possess one pair of antennae and a pair of mandibles.

Subphylum uniramia consists of 3 classes.

They are,

1.Class Diplopoda

2.Class Chilopoda

3.Class Insecta