The Dipnoi, commonly known as lung-fish, are considered to be specialised or degenerate descendants of the primitive lobe fins which they closely resemble. Dipnoi are Devonian offshoot from the crossopterygian stem. They still survive as three degenerate and specialised forms in widely separated tropical or subtropical, freshwater habitats of a special kind. Lung-fishes appear first in mid-Devonian, flourished moderately in [...]
In this article we will discuss about the representative types of chondrichthyes with the help of a suitable diagram. Sharks and Rays: 1. Heptanchus: Heptanchus is regarded as the most primitive shark. It is long bodied and slow moving. There are seven pairs of gill-clefts. Hexanchus, another primitive shark, has six pairs of gill-slits. Mouth is sub-terminal and there is [...]
In this article we will discuss about the classification of osteichthyes. The class Osteichthyes includes a large assemblage of true bony fishes. There are well over 30,000 to 40,000 living species, both freshwater and marine. Some of the freshwater forms are the carp, perch, bass, trout, catfish, sucker, etc., while the marine fishes are the tarpon, meckerel, tuna, sailfish, barracula, [...]