Acanthostega

A larger print vertical hatching may represent a swimming animal moving from top to bottom. b, On the left is a generic Devonian tetrapod based on Ichthyostega and Acanthostega fitted to the trackway.

Tetrapods are older than we thought! - The Panda's Thumb 2010

We note the large size of the print compared to the limbs of Ichthyostega and Acanthostega, and that the print appears to represent not just the foot but the whole limb as far as the knee. d, digit; fe, femur; ti, tibia; fi, fibula; fib, fibulare.

Tetrapods are older than we thought! - The Panda's Thumb 2010

II.1, left pes. b, Complete articulated left hind limb skeleton of Ichthyostega, MGUH f.n. 1349, with reconstructed soft tissue outline. c, Left hind limb of Acanthostega, reconstructed soft tissue outline based on skeletal reconstruction in ref.

Tetrapods are older than we thought! - The Panda's Thumb 2010

They are all Middle–Late Devonian in age, ranging from 385 million years (Panderichthys) to 365 million years (Acanthostega, Ichthyostega).

Casey Luskin embarrasses himself again - The Panda's Thumb 2010

Five of the most completely known are the osteolepiform Eusthenopteron; the transitional forms Panderichthys and Tiktaalik; and the primitive tetrapods Acanthostega and Ichthyostega.

Casey Luskin embarrasses himself again - The Panda's Thumb 2010

The scientists most responsible for our knowledge of it, Jenny Clack and Michael Coates of Cambridge University, believe that, like Ichthyostega, Acanthostega was largely a water-dweller, but it had lungs and its limbs strongly suggest that it could cope with land as well as water if it had to.

THE GREATEST SHOW ON EARTH RICHARD DAWKINS 2009

Another exciting discovery, also from tropical Greenland and also dating from the boundary between the Devonian and the Carboniferous, was Acanthostega.

THE GREATEST SHOW ON EARTH RICHARD DAWKINS 2009

Using this approach, Markey and Marshall found that in one key transitional species, the aquatic amphibian Acanthostega, the shapes of the junctions between adjacent skull bones are consistent with biting prey.

Ancient Amphibians Evolved A Bite Before Migrating To Dry Land 2007

Acanthostega, too, had a flat, amphibian skull and tetrapod-like limbs; but it too departed, and even further than Ichthyostega, from what we now think of as the fivefinger standard.

THE GREATEST SHOW ON EARTH RICHARD DAWKINS 2009

So, we are left with a gap between Panderichthys, the amphibian-like fish, and Acanthostega, the fish-like amphibian.

THE GREATEST SHOW ON EARTH RICHARD DAWKINS 2009