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Assertion 5.1: There are no transitional forms between fish and amphibians. Analysis: (i) The crossopterygian fish Eusthenopteron is linked to the early amphibian Icthyostega by a number of characteristics: Eusthenopteron has the same pattern of skill bones as Icthyostega. Eusthenopteron has internal nostrils, which are found only in land animals and sarcopterygians (a greater taxonomic group encompassing lungfish and crossopterygians). Eusthenopteron has teeth like those of amphibians. Eusthenopteron has a two-part cranium (icthyostegids are the only other vertebrates to have this characteristic) Eusthenopteron has the same vertebral structure as Icthyostega (list adapted from McGowan 1984:152-153) (ii) The skeletal characteristics of Acanthostega, the most primitive tetrapod known (360 million years), reveal that tetrapod anatomy evolved while our ancestors lived exclusively underwater -- and it evolved for life underwater. The first vertebrate that walked onto land didn't crawl on fins; it had evolved well-tuned legs millions of years beforehand. (Zimmer 1995:120) Acanthostega's arms could not support it very well on land, but were functional in water, allowing the creature to pull itself along the bottom of plant-rich coastal lagoons, and enabling it to ambush prey better than normal fish, which must move their fins to stay afloat, kicking up detectable waves. Additionally, despite being a tetrapod, Acanthostega breathed like a fish and had a hearing system more similar to that of fish than to that of landgoing creatures. (iii) Paleontologists have also found fragments from five more tetrapods, all of which were roughly contemporaries of Acanthostega and some of which were more advanced and thus closer to a terrestrial life. (Zimmer 1995:126) References McGowan C. 1984. In the Beginning...: A Scientist Shows Why the Creationists Are Wrong. Buffalo: Prometheus. Zimmer C. 1995. Coming onto the land. Discover 16(6):118-127.