The document discusses the classification of fishes throughout history. It describes early classifications by Muller, Berg, and Romer, which divided fishes into 6, 7, and 4 classes respectively. The current and most widely accepted classification is Nelson's from 1994, which uses a cladistic approach and evolutionary relationships to arrange fishes into subclasses under the subphylum Vertebrata. Nelson's classification places fishes in the grade Pisces and divides them into classes like Placodermi and Osteichthyes.

1. Classification of
Fishes

2. Position of Fishes in Phylum Chordata
Phylum-Chordata
Group: Craniata or Euchordata
Group: Acrania or Protochordata
1. Subphylum: Urochordata
2. Subphylum: Cephalochordata
1. Subphylum: Vertebrata
Agnatha Gnathostomata
1. Cephalaspidomorpha
2. Pteraspidomorpha
*Pisces Tetrapoda
1. Placodermi
2. Chondrichthyes
3. Acanthodi
4. Osteichthyes
1. Amphibia
2. Reptilia
3. Aves
4. Mammalia
Superclasses
Classes
Grade
Classes Classes
* Latin Piscis=Fish

3. • The first fossil vertebrates were found in the rocks of
ordovician period and named as Ostracoderms. They are
small, jawless, bony, fish like form related to cyclostomes.
• Devonian period is known as “The Golden Age of Fishes”.
• Swedish naturalist, Peter Artedi (1705-1735) is known as
“Father of Ichthyology”.
• Artedi established the methods and principles of systematic
Ichthyology so perfectly even Linnaeus could not alter it.
• Cuvier was the first to frame the classification on the basis of
external and internal characters of fishes.
• The classification proposed by Muller, Jordan, Regan, Berg,
Romer and Nelson considered to be the recent classification
of bony fishes.
• Currently, Nelson (1994) classification of fishes is in practice.
History of Classification of Fishes

4. Muller’s Classification
Muller classified fishes into six (6) sub-classes
Class: Pisces
Subclasses: Six
1. Dipnoi (Lung fishes)
2. Teleostei (Bony fishes)
3. Ganoidei (Polypterus, Amia, Lepidos)
4. Elasmobranchi (Sharks, Rays, & Rat fishes)
5. Marsipobranchii (Cyclostomes)
6. Leptocardii (Amphioxux)

5. Berg’s Classification (1940)
L. S. Berg classified fishes into seven (7) classes
Series: Pisces
Class: Seven
1. Pterichthys
2. Coccostei
3. Acanthodii
4. Elasmobranchii
5. Holocephali
6. Dipnoi
7. Teleostomi
Crossopterygii
Crossopterygii
Sub-class

6. Romer’s Classification (1971)
A. S. Romer (1971) arranged fishes into four classes
under super-class pisces.
Super-class: Pisces
Class: Four
1. Agnatha (Jawless vertebrates)
2. Placodermii (armoured or plate skinned fishes)
3. Chondrichthyes (Cartilagenous fishes)
4. Osteichthyes (Bony Fishes)

7. Romer’s Classification (1971)
1. Class: Agnatha (Jawless vertebrates)
Subclasses: 1. Monorhina
2. Diplorhina
2. Class: Placodermi (Armoured or plate skinned fishes)
Orders:
1. Petalichthyida
2. Rhenanida
3. Arthrodira
4. Phyllolepida
5. Ptyctodontida
6. Antiarchi

8. Nelson’s Classification (1994)
J. S. Nelson (1994) presented the classigication of
fishes in particular and chordata in general in a
linear order which reflects their postulated
evolutionary relationship (cladistic approcah).
Subphylum: Vertebrates
Super-classes: 1. Agnatha
2. Gnathostomata
Cephalaspidomorphii
Pteraspidomorphii
Class
Pisces
Tetrapoda
Grade

9. Nelson’s Classification (1994)
Grade: Pisces
Subgrade
Elasmobranchomorphii Teleostomi
1. Elasmobrabcchii
2. Holocepahali
Class
1. Placodermii
2. Chondrichthyes
Subclass
Class
1. Acanthodii (extinct)
2. Osteichthyes
Subclass
1. Dipeustei
2. Crossopterygii
3. Brachiopterrygii
4. Actinopterygii
Infraclass
1. Chontrostei
2. Holostei
3. Halecostomi (extinct)
4. Teleostei