The word Sarcopterygii is derived from the Greek words sarkos meaning flesh and pteryx meaning fin. Pindaca finned fishes belong to the class Sarcopterygiae. Their paired fins are fleshy hence they are known as lobe finned. They are known as lungfish and coelacanth. Lungfish are widespread in Africa, South America and Australia. Coelacanths are widespread along the coast of the Indian Ocean and Indonesia. Scientists believe that from this class of fish, amphibians emerged as quadrupeds and terrestrials. There are currently 8 species of fish alive.
Characteristics of Sarcopterygii
1. The endoskeleton is made up of endochondral bone.
2. Body covered with ganoid or cosmed scales. Cosmead starch contains cosmin.
3. Pinds have paired fins with fleshy lobes.
4. The caudal fin is diphysercal in nature. That is, the two parts of the caudal fin are united and are located around the tail as a uniform and flexible fin.
5. Bony gills are present on both sides of the head. They breathe through gills.
6. Their gills are covered by gills.
7. Their air sacs or patacas are rich in blood vessels and help them to swim and float.
8. Their heart has two chambers.
9. They are cold blooded or ectothermic animals. That is, their body temperature changes with the rise and fall of the environment temperature.
10. Their jaws have enamel covered teeth.
11. They are unisexual animals. They are external or internal.
[key words to remember features: endoskeleton, ganoid, cosmed, fin, diphycercal, gill, kanko, cracker, ectothermic, enamel]
Sarcopterygii bear evidence of evolution
1. Their endoskeleton is made up of bones. Therefore, the body structure is developed.
2. Body covered with ganoid or cosmed scales. It acts as an exoskeleton.
3. The body consists of paired fins with fleshy segments which are suitable for locomotion.
4. Their caudal fins are diphycircal in nature. It acts as a locomotor organ.
5. They have jaw teeth. Teeth are covered by enamel
6. There are air sacs in the body. It holds air and helps the fish float and breathe.
7. They are unisexual and occur either externally or internally
Some fishes of the class Sarcopterygii
Coelacanth – Latimeria chalumnae
Australian Long Fish – Neoceratodus forsteri
African Long Fish – Protopterus onnectens
South American Lungfish – Lepidosiren paradoxa
Lung fish
Those fishes whose air sacs have been converted into lungs are called lung fish. Lungfish belong to the class Sarcopterygiae. For example – Neoceratodus forsteri.
Ganoid scale
In bony fishes, rhomboid-shaped scales are called ganoid scales. It is also called Cosmed Aish. It is composed of cosmine. It is covered by enamel called ganyon.
Diphycercal
When two segments of the caudal fin of a fish are united to form a uniform and flexible fin, it is called diphyserical. Fishes of the class Sarcopterygiae have diphycercles. Eg – Latimeria chalumnae
Fish
Cold-blooded aquatic vertebrates that carry out respiration with the help of gills and move with the help of fins are called fish. The classes Myxini, Cephalospidomorpha, Chond