Fishes

          This is a group of vertebrate animals pertaining to two big branches:

A )     Cyclostomata : Which characterized by its round mouth in the form of sucker. Lamprey (Petromyzon) is an example of this branch.

 

B )     Gnathostomata

          Those are characterized by the presence of two pairs of double fins (thoracic and pelvic fins). Fishes of this branch divide into two classes :

1.       Class chondrichthyes : 

          Fishes of this class are characterized by their cartilaginous skeletons and disappearance of air bladder (which is necessary for floating in bony fishes). This class includes 3 groups :

a.       Sharks

b.       Skate and rays

c.       Chimaera

 

2.       Class Osteichtlyes :

          This class includes most of live fishes in fresh and salt water environments. They are characterized by their bony skeleton. This class divides into 2 sub-classes :

a.       Subclass : Sarcoperigii

          This subclass includes the pulmonary fishes with lobed fines in which they live in water with low oxygen concentration in Australia, Africa and South America.

 

B.      Subclass : Actinopterigii

          This group includes :

1.       Infraclass : Chondrostei.

2.       Infraclass : Holostei : which characterized by its shinning scales.

3.       Infraclass : Teleostei :

          This group is divided into fishes with soft fins since the spikes are soft also, and fishes with spiked fines. This group represents the majority of the live fishes (90 %) which includes the economic fishes of the world. Most of the fish samples present in the museum belong to class Osteichthyes (bony fishes) with small and medium size. some of them are preserved and showed in preservative solutions and the others are mummified.