came a magnet for competing Scandinavian geolo- 

 gists, with Ichthyostega as one of the prizes. 



At the time of Ichthyostega's discovery, another crea- 

 ture from East Greenland, called Acanthostega, was 

 known; it had been identified in the 1940s as a sec- 

 ond kind of early tetrapod, on the basis of two in- 

 complete skulls. Those tantalizing skull fragments 

 were from the same time (and, evidently, the same 

 place) as the fossils of Ichthyostega: from the Late De- 

 vonian, about 365 million years ago. Because of the 

 movements of continents driven by plate tectonics, 

 Greenland has not always been an Arctic island; in 

 the Late Devonian, it was part of a huge landmass 

 at the equator and was rich with the life-forms of 

 the period [see map on next page] . Hence Greenland 

 beckoned to paleontologists as the probable site of 

 one of the great events in the history of life on earth. 



In the summer of 1987 I was fortunate to get the 

 chance to explore several places in central East Green- 

 land where more Devonian tetrapods were likely to 

 be found. Mounting a Greenland expedition was a 

 daunting prospect for a novice like me. It required 

 ample stores of food, a radio-support network, heli- 



copters to get in and out of the region, and firearms 

 to ward off polar bears and musk oxen. As luck would 

 have it, a team of Danish scientists from the Green- 

 land Geological Survey was completing a three-year 

 project in the same area my colleagues and I wanted 

 to explore and had all the logistical resources in place 

 to serve our expedition. Thanks to their good offices, 

 the expedition was blessed with success. 



We pinpointed a prime site 2,600 feet up a steep 

 mountainside. During our first days in the field, the 

 climb to the site took us most of a day, but by the 

 end of four weeks, we could scramble up in just 

 two and a half hours. With twenty-four hours of 

 daylight, we could spend a long spell on the moun- 

 tain. The fossils we discovered were well worth the 

 effort; on returning from the field, we had enough 

 of them to recreate the anatomy of Acanthostega and 

 its mode of locomotion. And in the same general 

 location, though in slightly different sediment beds, 

 we found a few remains of Ichthyostega. The story 

 of the transition from water to land began to gath- 

 er momentum. 



The Greenland fossils and subsequent discoveries 



Aquatic tetrapods, or four-legged swimmers, evolved during the Devonian period (between 

 416 million and 359 million years ago) to become the first four-legged land animals, as fins were 

 transformed into limbs with fingers and toes. The four animals shown below (not to scale) are 

 (left to right): Eusthenopteron, Tiktaalik, Acanthostega, and Ichthyostega. Limbs might have 

 given an advantage to transitional forms such as Tiktaalik in navigating swampy waters or in 

 pushing across the bottoms of riverbeds; eventually, the limbs of some tetrapods became able 

 to bear weight on land. The insets show the creatures' right forelimbs (except for Ichthyostega, 

 which is a right hind limb); the scale bars each represent one inch. 



