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143 5 The First Feet: Tetrapods of the Famennian By the latter part of the Late Devonian, the Famennian, vertebrates with indisputable limbs bearing digits—tetrapods—had appeared. Some remarkably well-preserved material from several localities provides details of their anatomy and lifestyles. This chapter examines each of these in turn, and then goes on to see what pointers they may give to the origin of the group. It is East Greenland that has provided the most detailed knowledge of Devonian tetrapods. East Greenland has been studied by geologists for many decades. One of the reasons is that the terrain lies within the polar semidesert , so it is relatively sparsely vegetated and the geology can be seen during the short summer season, when the ice and snow melt around the coast. At the same time, in contrast to many desert areas, availability of water is not a problem for the visiting scientists, though they are often plagued by mosquitoes, and accessibility to the area is often hampered by bad weather. Most of the sites are usually only reached by helicopter, though in the past, icebreakers carried the scientific teams to the fjords from where they reached the sites by inflatable dinghies. Some of the most recent collecting expeditions have been carried out in collaboration with the Denmark and Greenland Geological Survey, who use as their base camp the Danish air force airstrip of Mestersvig. Part of the central area of East Greenland is composed of rocks representing the Middle and Late Devonian period, and the area around Kejser Franz Joseph Fjord, which lies 400 kilometers north of the Arctic Circle, has been noted for yielding fossils of Devonian vertebrates since the early years of the 20th century. The main localities are gathered around Celsius Bjerg on Ymer Ø and the mountains of Sederholm, Smithwoodward, Stensiö, and Wiman Bjerg that make up the peninsula of Gauss Halvø (Fig. 5.1). All the East Greenland Devonian tetrapod localities and the specimens derived from them are documented in Blom et al. (2005, 2007). From the late 1920s until the mid-1950s, a series of expeditions undertaken jointly by Danish and Swedish paleontologists brought back remarkable finds of fishes and what were then the earliest known tetrapods . Two genera of tetrapod from this area have become particularly well known from extensive collections. Ichthyostega was the first genus of Famennian Tetrapods from East Greenland Gaining Ground 144 5.2. Jarvik’s (1996) reconstruction of Ichthyostega. 5.3. (Color Plate 5) Three of the 1998 expedition members: from left to right, Becky Hitchin, Sarah Finney, and the author. The photograph was taken by the fourth expedition member, Sally Neininger (S.L.N.). The First Feet 145 Devonian tetrapod to become established in textbooks, scientific articles, and popular and children’s books (Fig. 5.2). It is sometimes referred to as the four-legged fish. Many specimens of this creature were found during the early years of exploration of East Greenland, and these are vividly described by Jarvik (1996) in his monograph on the animal. Acanthostega gunnari was named and described from two specimens in 1952 (Jarvik 1952), but since then, it has become much better known thanks to collections made during the summer of 1987, when a joint expedition from Cambridge, England, and Copenhagen, Denmark, returned to the area (Bendix-Almgreen et al. 1990; Clack 1988). A follow-up expedition that I led in 1998 collected new ichthyostegid material, and we discovered a 5.4. (Color Plate 6) I am seated in front of Stensiö Bjerg in 1998. Photograph by S.L.N. Gaining Ground 146 bit more about the circumstances in which the tetrapods were deposited (Clack and Neininger 2000). This expedition was supported by the National Geographic Society. Figure 5.3 shows three of the expedition members on Gauss Halvø, on a reconnaissance trip, and Figure 5.4 shows me seated at the 1998 campsite under the brow of Stensiö Bjerg. When Ichthyostega and Acanthostega were alive, Greenland would have been in tropical latitudes. The climate of the region seems to have been monsoonal, and the animals lived in an extensive river basin fed by meandering streams flowing from mountains to the south. These fed into a large freshwater lake or inland sea whose margins were determined by a series of faults, cutting a broad parallel-sided valley into the mountains of the Old Red Sandstone continent (Olsen and Larsen 1993; Olsen 1993; Larsen et al. 2008). Along the peninsula now called Gauss Halvø, tetrapods...

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