Tiktaalik de nuevo/Tiktaalik again

Tiktaalik roseae fue descubierto en Canadá por un equipo investigador norteamericano liderado por Edward B. Daeschler. El descubrimiento se publicó en la revista Nature en el año 2006. Este fósil es muy importante porque viene a llenar un hueco en la transición entre peces y anfibios, y proporciona la clave acerca de como se produjo dicha transición.
La revista Nature publicó ayer, 16 octubre de 2008, los resultados de nuevas investigaciones del equipo descubridor (A Devonian tetrapod-like fish and the evolution of the tetrapod body plan) demostrando que "Entre los cambios morfológicos que ocurrieron durante la transición 'pez-animal de cuatro patas', tuvo lugar una marcada reorganizaciónn del endoesqueleto craneal."
La especie ha vuelto a ser de actualidad, pues se han aportado nuevos datos: El análisis de la cintura pélvica y la aleta trasera de la especie de unos 375 millones de años de edad, ofrece nuevos detalles sobre el vínculo evolutivo entre los peces y los vertebrados terrestres, según estudio que publica la revista norteamericana Proceedings of the National Academy of Sciences. Sus resultados revelan que la evolución de las patas traseras en realidad comenzó como un aumento de las aletas traseras.

Tiktaalik roseae was discovered on Canada by an american research team lead by Edward B. Daeschler. This dicovery was reported in 2006 by means of a scientific paper published in Nature. This fossil is very important because it fills in a gap in the transition from fish to amphibians and provides clues as to how the transition took place.
Nature published yesterday, October 16, 2008, the results of new researchs of the discovering team (A Devonian tetrapod-like fish and the evolution of the tetrapod body plan) showing that "Among the morphological changes that occurred during the 'fish-to-tetrapod' transition was a marked reorganization of the cranial endoskeleton."
This species is again on the news: the analysis of the pelvic girdle and fin of the 375 million years species, shows new details about the evolutionary link between fish and terrestrial vertebrates. The study has been published in the Proceedings of the National Academy of Sciences of USA, and its results reveal that the rear limbs evolution started with the increase of the rear fins.
Para saber más/To know more
Tiktaalik roseae: The Search for Tiktaalik
Tiktaalik (Spanish wikipedia)
Tiktaalik (English wikipedia)
Tiktaalik roseae – a missing link?

Resumen de la publicación/Abstract of the paper
Pelvic girdle and fin of Tiktaalik roseae
Neil H. Shubin, Edward B. Daeschler and Farish A. Jenkins Jr
Abstract
A major challenge in understanding the origin of terrestrial vertebrates has been knowledge of the pelvis and hind appendage of their closest fish relatives. The pelvic girdle and appendage of tetrapods is dramatically larger and more robust than that of fish and contains a number of structures that provide greater musculoskeletal support for posture and locomotion. The discovery of pelvic material of the finned elpistostegalian, Tiktaalik roseae, bridges some of these differences. Multiple isolated pelves have been recovered, each of which has been prepared in three dimensions. Likewise, a complete pelvis and partial pelvic fin have been recovered in association with the type specimen. The pelves of Tiktaalik are paired and have broad iliac processes, flat and elongate pubes, and acetabulae that form a deep socket rimmed by a robust lip of bone. The pelvis is greatly enlarged relative to other finned tetrapodomorphs. Despite the enlargement and robusticity of the pelvis of Tiktaalik, it retains primitive features such as the lack of both an attachment for the sacral rib and an ischium. The pelvic fin of Tiktaalik (NUFV 108) is represented by fin rays and three endochondral elements: other elements are not preserved. The mosaic of primitive and derived features in Tiktaalik reveals that the enhancement of the pelvic appendage of tetrapods and, indeed, a trend toward hind limb-based propulsion have antecedents in the fins of their closest relatives.