[N] 2006 Tiktaalik roseae, a Devonian tetrapod-like fish
20060409
Daeschler, E.B., Shubin, N.H. and Jenkins, F.A. Jr. (2006). A Devonian tetrapod-like fish and the evolution of the tetrapod body plan. Nature 440: 757-763. [Tiktaalik roseae]
Abstract: \\\\\\\"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.\\\\\\\"
Shubin, N.H., Daeschler, E.B. and Jenkins, F.A. Jr. (2006). The pectoral fin of Tiktaalik roseae and the origin of the tetrapod limb. Nature 440: 764-771.
Abstract: \\\\\\\"Wrists, ankles and digits distinguish tetrapod limbs from fins, but direct evidence on the origin of these features has been unavailable. Here we describe the pectoral appendage of a member of the sister group of tetrapods, _Tiktaalik roseae_, which is morphologically and functionally transitional between a fin and a limb. The expanded array of distal endochondral bones and synovial joints in the fin of _Tiktaalik_ is similar to the distal limb pattern of basal tetrapods. The fin of _Tiktaalik_ was capable of a range of postures, including a limb-like substrate-supported stance in which the shoulder and elbow were flexed and the distal skeleton extended. The origin of limbs probably involved the elaboration and proliferation of features already present in the fins of fish such as _Tiktaalik_.\\\\\\\"