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Out of Order

New Fossil Raises Questions about Tetrapod Origins

The fishapods are not the latest rock n’ roll sensation. But members of this group have achieved rock-star status–at least among paleontologists.

Fishapods refer to series of fossils recovered from rock formations that date between 385 and 365 million years in age. These extinct creatures seem to document the evolutionary transition from lobe-finned fish to amphibians, which were the first animals on land. Fishapods possess characteristics interpreted as varying mixtures of fish and amphibian features. At first glance, these animals appear to delineate a key evolutionary transition–the movement from water to land–supporting a strictly naturalistic explanation for the emergence of life on land.

Among paleontologists fishapods are superstars because they represent one of the few examples of what appears to be a transitional sequence. Over the last 150 years, paleontologists have been repeatedly confronted with the fact that the fossil record displays abrupt appearances of new forms and a scarcity of transitional intermediates, not expected if evolution proceeds in small, successive steps as Darwin envisioned.

But as I have recently pointed out several new fishapod discoveries raise irritating questions for evolutionary biologists. And the questions continue with new work just published evinces.

One of the problems with an evolutionary interpretation of the fishapods is that these creatures appear to be out of order. For example, Ventastega, an animal that lived about 365 million years ago, is thought to occupy a halfway point between Tiktaalik and amphibians. (Tiktaalik is thought to occupy the midpoint between lobe-finned fish and amphibians) Its skeletal features indicate that it’s out of sequence. Older fishapods actually exhibit more advanced features than those of Ventastega.

Another fishapod, Panderichthys, causes the same problem. This creature existed about 385 million years ago and is considered to be much closer to a lobe-finned fish than an amphibian. Yet, it has digits at the end of its fins, whereas Tiktaalik, considered to be more advanced, doesn’t. Again, the fossils are out of sequence.

The same difficulty also exists for Acanthostega and Ichthyostega. These creatures lived about 370 to 360 million years ago and are considered to be among the first amphibians. Traditionally, evolutionary biologists thought that Acanthostega was more primitive than Ichthyostega. Based on new fossil finds, it now looks like the opposite is true; Ichthyostega was more primitive than Acanthostega. Interestingly, Ichthyostega spent more time on the land than Acanthostega. In fact, Acanthostega, presumably more evolutionarily derived, was essentially an aquatic animal.

I think that fishapods are best understood as the work of a Creator. These animals were perfectly suited to live at the water’s edge. And the mosaic of fish and tetrapod characteristics possessed by the fishapods signifies design. Human designers frequently design objects that blend properties and features of different systems. If humans make mosaics, why wouldn’t a Creator do the same?

These fascinating creatures, well-designed to exploit their environment, sing of creation. Conversely, overlapping fishapods that appear in the “wrong” order in the fossil record indicate that the long-sought “innumerable transitional forms” still don’t exist.

Other related resources:

10 Breakthroughs of 2010 (booklet)

Science News Flash May 24, 2010 “Ancient Mass Extinction May Have Paved Way for Modern Species”