Zoology Distinguish between Tiktaalik Ichthyostega and Acant

Solution

Ichthyostega is closely related to Tulerpeton and living tetrapods. The lineage that leads to tetrapods had weight bearing elbows, bending wrist regions, and separation between the body, neck and head. This lineage gave rise to Tiktaalik, Ichthyostega, Acanthostega, Tulerpeton and living tetrapods.

Tiktaalik is a fossil fish that reduces the gap between Panderichthys and tetrapod Acanthostega. Tiktaalik is the lobe-finned fish that are more diverse. This fish share some features with that of amphibians. Tiktaalik is also considered to be an intermediate between the lobe-finned fish Panderichthys and first four-limbed animals, Ichthyostega and Acanthostega. Ichthyostega has imbricate ribs which are not present in Acanthostega and Tiktaalik. The ribcages of Tiktaalik and Ichthyostega are entirely different from each other.

The gap between the pectoral fin of Tiktaalik and front foot of Acanthostega is large. A number of features like body scales, fin rays, lower jaw, and palate appear similar to the sarcopterygians that are less advanced. The anatomy is found to have undergone a lot of changes in between the Tiktaalik and earliest tetrapods. According to the fossil records Acanthostega and Ichthyostega are dead-ends and there is a large gap observed after Ichthyostega.