The upcoming discussion will update you about the differences between Chondrichthyes and Osteichthyes.
Difference # Chondrichthyes:
1. The mouth is ventral in position.
2. The body is covered with minute and microscopic placoid scales, the skin is tough.
3. Paired pelvic fins are provided with claspers in males.
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4. The tail is heterocercal, the vertebral column extending into the dorsal part of the caudal fin.
5. The head is dorsoventrally flattened.
6. Gill slits, usually five pairs, open separately and directly to the exterior.
7. The gills are hemi branch/holobranch.
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8. Operculum always absent.
9. A spiracle usually present.
10. The endoskeleton is cartilaginous, with amphicoelous vertebrae.
11. A conus arteriosus is present. Aortic arches five pairs.
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12. A spiral or scroll valve is present in the intestine.
13. Stomach with distinct cardiac and pyloric regions. Intestinal caecum absent.
14. Generally carnivorous, with a short intestine.
15. Gut with valves at all the junctions.
16. Cloaca present.
17. An optic chiasma is present.
18. An air bladder is absent.
19. Gills with intra-branchial septum.
20. Testes are connected with the kidneys.
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21. Kidneys elongated and narrow, with anterior non-renal and posterior renal portion.
22. The eggs are large and except one species, provided with horny case.
23. In some cases, development takes place within the oviducts and the young ones are born alive.
24. In the embryo, gills project from the gill clefts as filaments.
25. Marine.
Difference # Osteichthyes:
1. The mouth is apical in position.
2. The body is covered with cycloid or ctenoid or ganoid scales. The skin is soft. Complete absence of scales in cat fish group.
3. Claspers are absent.
4. The tail is homocercal, the vertebral column ends at the middle of the base of the caudal fin.
5. The head may be dorsoventrally or laterally flattened.
6. Gill slits, usually four pairs, open in a gill chamber.
7. The gills are holobranch.
8. Operculum with branchiostegal membrane always present.
9. A spiracle is absent.
10. The endoskeleton is bony with amphicoelous vertebrae.
11. A conus arteriosus is absent. Aortic arches four pairs.
12. A spiral valve in the intestine is absent.
13. Stomach not -differentiated into cardiac and pyloric portion. Intestinal caecum present.
14. Generally omnivorous, with a short or long intestine.
15. Valves few and far between.
16. Cloaca absent.
17. An optic chiasma is absent.
18. An air bladder is usually present.
19. Intra-branchial septum absent or rudimentary.
20. Testes are not connected with the kidneys.
21. Kidney renal, fused, with a broad anterior and a narrow posterior portion.
22. The eggs are small but heavily yoked and without horny cases.
23. With a few exceptions, the young are hatched in an immature condition and undergo larval development.
24. Gill filaments remain covered by operculum.
25. Marine and fresh water forms.