Classification of vertebrate zoology (Class Pisces)

Classification of vertebrates zoology

Vertebrates are the animals belonging to the  sub phylum vertebrata of the phylum chordata.

Sub phylum vertebrata is divided into the following five classes.

1.   ClassPisces (Fishes)
2.   Class Amphibia (Amphibians)
3.    Reptila (Reptiles)
4.   Aves (Birds)
5.     Mammalia (Mammals

Class Pisces (Fishes);

Definition of Fishes;

Fishes are cold blooded vertebrate with gills and fins and wholly living in water. Approximately 28000, species of fishes are present throughout the world.

General Characters of Pisces/Fishes;

v  They are clod blooded, aquatic vertebrates having stream lined body.

v  They have paired appendages in the form of pectoral and pelvic fins, supported by skeletal fin rays.

v  The skin with exoskeletal of dermal scales.
v  Their body is distinguished into head, trunk and tail. Tail is powerful propulsive organ.
v  Their head carries mouth, paired eyes, nostrils and trunk possesses 5 pair of gill slit.
v  They are having true jaws and teeth.
v  They are having heart that consist of two chambers, one is auricle and other is ventricle.
v  The respiration take place in their body by five pairs of gills.
v  Sexes are separate fertilization may be external or internal.
v  The excretions occur in their body by mesonephric kidney.
v  In fishes middle and external ears are absent and internal ears are mainly balancing organs.

 “In this class Pisces or fishes are considered as Superclass” 

The superclass Pisces is further distinguished into four classes:

1.    Placodermi (Extinct Species)
2.   Chondrichthyes ( Elasmobranchi)
3.    Osteichytes (Telesotomi)
4.    Dipnoi

v Class 1 Placodermi (Extinct Species)
v Class 2 Chondrichthyes ( Elasmobranchi)

Term chondrichthyes drive from Greek word Chondros mean cartilage and Ichythes mean fishes. It is distinguished into two subclasses.

1.      Subclass1. selachii
2.      Subclass2. Bradyodontii

Subclass 1. Selachi;

In this subclass includes living as well as extinct sharks, rays and dogfishes. The extinct forms are grouped under protoselachii and modern living forms under euselachi. Euselachii is separated into two orders.

Order 1. Pleurotremata   (pleuro mean sides and trema mean opening)

Examples: Scolidon, seyliorhinkus, Sphyrna, squalus and sharkes.

Order 2. Hypotremata;

It is drived from greek word hypo mean belw and trema mean opening.

Examples: Tygon, Torpedo, Raja (ray) and skates.

Subclass2: Bradyodontii.

It is divided into following orders.

Order 1. Eubradyodonti.

It includes modern forms as Heldous.

Order2. Holocephli.

It includes modern forms such as chimaeras.

v Class 3. Osteichithyes (teleostomi)

It is drived from Greek word osteos mean bone and ichthyes mean fishes. The class osteichithyes is distinguished into three subclasses;

1.      Subclass1. Palaeopterygii
2.      Subclass 2. Actinopterygii
3.      Subclass 3 choanichthyes (fossils fishes)

Subclass1. Palaeopterygii. It includes two orders.

Order 1. Polypteriforms or ploypterini or clasdistia;

Examples: Pllypterus and Polypterous.

Order2. Acipenseriformes or chondrostei.

Examples: Ascipenser and polydon.

Subclass 2. Actinopterygii or Neopterggii or Teleostomi.

It is derived from both latin and Greek word. The term Actino derived from latin word means having rays and pterygii derived from Greek word pterux means wings’ fins.

Subclass 3 choanichthyes (fossils fishes) .

A subclass of teleostomi comprising fishes with internal nares and they were dominant but nearly now extinct. It includes crossopterygii.

v Class Dipnoi.

Commonly know as lung fishes, since they posses functional lungs with external and internal nares.

Examples: protopterous,Lepidosiren and Neoceratodus.

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