CLASSIFICATION OF ARTHROPODA
Phylum Arthropoda is further classified into 4 distinct Sub-phyla:
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Trilobitomorpha
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Chelicerata
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Mandibulata
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Onychophora
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TRILOBITOMORPHA
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Extinct species.
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Oval body composed of 3 lobes.
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All segment except the last segment possesses the biramus appendages.
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A pair of segmented antenna present on the head.
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Ex- Dalmanites

2. CHELECERATA
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Body is divisible into cephalothorax and abdomen.
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Antennae and mandibles are absent.
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Sub-phylum Chelicerata is again divided into 3 different classes, which are as follows:
1. MEROSTOMATA
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Marine animals.
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Abdomen with appendages modified into gills.
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Telson present at the posterior end of the body.
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Compound eyes are present laterally at the anterior end.
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Ex- Limulus.
2. ARACHNIDA
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They may be terrestrial or aquatic.
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Telson may or may not be present.
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Anterior half of the abdomen bears a dorsal tubular heart.
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Simple eyes are present.
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Ex- Spiders, Scorpions etc.
3. PYCNOGONIDA
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Small sized sea spiders.
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Body bears large cephalothorax and small abdomen.
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Excretory and respiratory organs are absent.
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8 pairs of walking legs are found.
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Ex- Nymphon.
3. MANDIBULATA
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Body is divisible into head, thorax and abdomen.
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Head possesses segmented appendages which includes one or two pairs of antennae, a pair of mandible and one pair of maxilla.
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In addition to compound eyes, simple eyes or occeli are present.
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Sub-phylum Mandibulata is again divided into 6 different classes, which are as follows:
1. CRUSTACEA
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Mostly aquatic forms.
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Exoskeleton is made up of chitinous cuticle consisting of calcium carbonate & calcium phosphate.
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Body is divisible into cephalothorax and abdomen.
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Head bears 2 pairs of antennae, one pair of mandible and two pairs of maxillae.
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Respiration occurs through gills.
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Ex- Prawn.
2. DIPLOPODA
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Most of them are terrestrial, but some are aquatic.
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Exoskeleton is calcified.
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Body is divisible into head, thorax and abdomen.
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Respiration is carried out by unbranched tracheae.
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Ex- Julus.
3. CHILOPODA
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Terrestrial animals.
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Exoskeleton is uncalcified.
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Body is divisible into head and trunk.
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Respiration takes place by tracheae.
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Ex- Scolopendra.
4. SYMPHYLA
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Terrestrial animals, found mostly in agricultural habitat.
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Body is divisible into head and trunk.
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Head bears one pair of antennae, one pair of mandible and two pairs of maxillae.
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Respiration takes place by tracheae.
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Ex- Symphylella.
5. PAUROPODA
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Terrestrial in habitat, mostly found in soil and litter habitat.
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Body is divisible into head and trunk.
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Eyes are lacking.
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Respiration by general body surface.
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Ex- Pauropoda.
6. INSECTA
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Mostly terrestrial, some are aquatic.
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Body is divisible into head, thorax and abdomen.
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Chitinous exoskeleton is present.
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Respiration is generally by tracheae.
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Fertilization is internal.
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Ex- Cockroach.
4. ONYCHOPHORA
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Terrestrial in habitat.
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These are the primitive, vermiform, unsegmented animals.
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Single pair of antennae, eyes and jaws are present.
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Numerous stumpy, unjointed clawed legs are found.
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Ex- Peripatus.









