January 31, 1910 (a Monday)

Ichthyostega

On this date, the Swedish geologist and paleontologist Gunnar Säve-Söderbergh was born. He took bachelor’s and licentiate’s degrees at Uppsala University in 1931 and 1933, respectively, and was appointed professor of historical geology at Uppsala in 1937.

In 1928, Säve-Söderbergh led a team that discovered extraordinarily fossiliferous beds in the upper Devonian of east Greenland. These 360-million-year-old rocks contained numerous fossils of bony fish and one set of particularly interesting remains. These latter fossils possessed a fish-like tail, ribs, and back, yet also had limbs with fingers and toes. This new species was dubbed Ichthyostega by Säve-Söderbergh in 1932 and was described in a series of papers by Erik Jarvik. It is widely featured in the scientific literature as the first “four-legged fish”. Although Ichthyostega may not be the ancestor of today’s terrestrial vertebrates, it no doubt is a transitional form.

The hind limb of Ichthyostega.

Ichthyostega‘s combination of fish and amphibian characters led to speculation about how the origin of tetrapods and the invasion of land by vertebrates could be related. One hypothesis, formulated by Joseph Barrell and later revised by Alfred Romer, held that one group of fish, such as Ichthyostega, adapted to more terrestrial environments due to the drying of Devonian ponds. Recent discoveries have changed this conception entirely.

Säve-Söderbergh was made an honorary doctor at Uppsala in 1942 and was elected a member of the Royal Swedish Academy of Sciences in 1948. Unfortunately, tuberculosis put an untimely end to his career. He died in 1948 at Solbacken, a sanatorium in Dalarna, Sweden.

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