Journal Article

A Devonian tetrapod-like fish and the evolution of the tetrapod body plan

Jenkins, Farish A., Daeschler, Edward B., Shubin, Neil H.

2006

Overview

The relationship of limbed vertebrates (tetrapods) to lobe-finned fish (sarcopterygians) is well established, but the origin of major tetrapod features has remained obscure for lack of fossils that document the sequence of evolutionary changes. Here we report the discovery of a well-preserved species of fossil sarcopterygian fish from the Late Devonian of Arctic Canada that represents an intermediate between fish with fins and tetrapods with limbs, and provides unique insights into how and in what order important tetrapod characters arose. Although the body scales, fin rays, lower jaw and palate are comparable to those in more primitive sarcopterygians, the new species also has a shortened skull roof, a modified ear region, a mobile neck, a functional wrist joint, and other features that presage tetrapod conditions. The morphological features and geological setting of this new animal are suggestive of life in shallow-water, marginal and subaerial habitats. When fins became limbs The transition between fishes and limbed vertebrates, or tetrapods, occurred over 370 million years ago and required changes to virtually the entire body. Sensational fossil finds, and reinterpretations of old ones, have radically altered thinking on this topic in the past 20 years. But the transition itself – the very point where fishes became tetrapods – remains obscure. What fossils there are tend to be incomplete or badly preserved. All that changes with the discovery of remarkable new fossils from the late Devonian of Canada of a near-complete transitional form preserved in the round. It's a fish with fins, but fins that flexed and extended like arms and hands. It has tetrapod-like ribs, a mobile neck and wrist. The impact of this discovery will be felt far and wide in evolutionary biology. On the cover, the fossil as found emerges from under a log as it might have in life in a shallow-water habitat. The discovery of the fossil remains of a tetrapod-like fish sheds light on the order in which important tetrapod characters arose.

• Publisher: Nature Publishing Group UK,Nature Publishing,Nature Publishing Group
• Subject: Animals / Biological Evolution / Devonian / Earth sciences / Earth, ocean, space / Environment / Evolution / Exact sciences and technology / Extremities - anatomy & histology / Extremities - physiology / Fish / Fishes - anatomy & histology / Fishes - classification / Fishes - physiology / Fossils / History, Ancient / Humanities and Social Sciences / Morphogenesis / multidisciplinary / Paleontology / Phylogeny / Pisces / Science / Science (multidisciplinary) / Shallow water / Skull - anatomy & histology / Tetrapoda / Vertebrate paleontology / Vertebrates / Water