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VERTEBRATA

It is divided into two parts - 1. Agnetha 2. Gnetha

S.No.	Character	Agnetha	Gnetha
1	True Jaws	Absent	Present
2	Paired apendages	Absent	Present
3	Semi circular canal in internal ear	2	3
4	Nostril	1	2

1.	AGNETHA
	Agnetha is divided into two parts -	1. Ostracodermi	2. Cyclostomata

(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

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Biology, Academics

Category:- Biology
Reference No.:- M9509710

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