What are Lob-Finned Fishes and their role in evolutionary behaviour?

 What are Lob-Finned Fishes?

Introduction:

 Lob-finned fishes are also called sarcopterygian, derived from the Ancient Greek words “flesh”, and “fins or wings”.Moreover, this clade of organisms possesses teeth.

Primitive lobe-finned fishes were mostly bony fish having fleshy, lobed, and paired fins, these fins get attached to the body with the help of a single bone. Lobe-finned fishes are different from all other fishes due to the formation of their fins, they possess fins that are born on the basis of flesh and lob-like structure and they are stalked out from the body to the outer side. 

The scales of lobe-finned fishes, the Sarcopterygians consist of lamellar bone surrounded from all sides by layers of vascular bones, external keratin, and dentine-like cosmine and, are called true scaloids scales. Tetrapodomorphs evolved from lobe-finned fishes. These fishes possess morphology that is like the tetrapods, and they provide indications of the transition from aquatic organisms to terrestrial ones.

They possess the. both pectoral and pelvic fins have resembling those of tetrapod limbs. The very first tetrapod land vertebrates and basal amphibian organisms have legs which were evolved from these fins.

Opposing one of the characteristic features of ray-finned fishes. lobe-finned fishes or sarcoptergiansretain two dorsal fins. with their separate origins.

The sarcopterygians have a braincase having a hinge line, but tetrapods and lungfishes lost this feature. Many primitive sarcopterygians have tails with equal lobes which are called the symmetrical tail. One of the important features of all sarcopterygians is the possession of teeth which are also covered with protective enamel coats. Most species of lob-finned fishes are extinct, according to paleontologists the known extinct, non-tetrapod lobe-finned fishes include two species of coelacanths and six species of lungfishes.

Classification:

Kingdom: Animalia

Phylum: Chordata

Clade: Euteleostomi

Class: Sarcopterygii

Evolutionary Behaviour:

The paleontologists and their research and record make this thing clear that in Devonia Era, almost 400 million years ago the terrestrial organisms especially, vertebrates evolved from lobe-finned fishes so these are also members of the class sarcopterygian. But the only terrestrial vertebrates who are still living in today's age are the four-limbed organisms, the tetrapods, which evolved almost 350 million years .