VERTEBRATA
It is divided into two parts - 1. Agnetha 2. Gnetha
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S.No.
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Character
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Agnetha
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Gnetha
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|
1
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True Jaws
|
Absent
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Present
|
|
2
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Paired apendages
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Absent
|
Present
|
|
3
|
Semi circular canal in internal ear
|
2
|
3
|
|
4
|
Nostril
|
1
|
2
|
|
1.
|
AGNETHA
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|
|
|
Agnetha is divided into two parts -
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1. Ostracodermi
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2. Cyclostomata
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(I) OSTRACODERMI
- First vertebrate. Greatly armoured. All fossils.
EXAMPLES - Cephalospis
(II) CYCLOSTOMATA
Body eel like. Mouth sucker type. Ectoparasite.
Gills 5-16 pairs. Pineal eye present.
Unicellular shin glands present.
Scales absent. Sanguivorous.
On tongue horny teeth present.
EXAMPLES -
1. Petromyzon - lamprey, lampredin present, 7 pairs gills, larva is ammocoet for seven years, living fossil
2. Myxine - Hag fish, lips as of old lady, bisexual, development direct
Note :- Before pisces & after cyclostomata placodermi is a group of extinct fishes (jawed).
These are most primitive fishes. Example- climatius
2. GNETHA
Gnetha is divided into 5 classes -
1. Pisces
2. Amphibia
3. Reptilia
4. Aves
5. Mammalia