German researchers have found fossil evidence showing ancient tetrapods living 290 million years ago could re-grow limbs. This illustration shows the Lower Permian amphibian Micromelerpeton undergoing limb regeneration, resulting in a regenerated limb with a typical malformation
En la actualidad las salamandras son los únicos tetrápodos que pueden regenerar su cola y sus miembros si los pierden. Esta capacidad se ha relacionado con un desarrollo de los dedos primero y segundo de este animal antes que el resto, aunque el modo en que se produce todavía es desconocido.
Un nuevo estudio, publicado en Nature esta semana, revela que esta habilidad podría remontarse a hace unos 290 millones de años, según sugieren los análisis de los miembros y la cola de algunos anfibios fósiles de esta época como el Micromelerpeton (representado en la imagen).
Los resultados del trabajo, liderado por el Leibniz Institute for Evolution and Biodiversity Science (Alemania), evidencian que el sistema regenerativo propio de las salamandras ya se daba en estas especies extintas y que esta función se daba al menos 80 millones de años antes de lo que indican los primeros registros fósiles.
Según los autores, la formación de nuevas extremidades podría ser un atributo más extendido en el pasado entre los tetrápodos. Estas capacidades regenerativas se fueron perdiendo durante la evolución de estos seres vivos.
Researchers have previously suggested the ability may be linked to the way the amphibian develops its limbs, with the first and second digits forming before the others.
Dr Nadia Fröbisch, of Leibniz Institute for Evolution and Biodiversity Science in Berlin, said: 'Salamanders…form their fingers in a reversed order compared to all other four-legged vertebrates - a phenomenon that has puzzled scientist for over a century.
Dr Fröbisch and her colleagues examined limb and tail details in fossil amphibians from rocks dating back to the Upper Carboniferous about 290 million years ago. This image shows the Lower Permian amphibian Sclerocephalus from the Saar-Nahe Basin in south west Germany
‘The question we wanted to address was if and how this different way of developing limbs is evolutionarily linked with the high regenerative capacities.’
In a bid to solve the mystery Dr Fröbisch and her colleagues examined limb and tail details in fossilised amphibians from rocks dating back to the Upper Carboniferous period, about 290 million years ago.
They found the same methods of regeneration were in these relatives of modern salamanders.
This implies these features were present at least 80 million years before the first occurrence of salamanders in the fossil record, according to the findings published in the journal Nature.
The results suggest that limb regeneration might once have been a more widespread attribute.
Dr Frobisch explained: ‘The high regenerative capacities were lost in the evolutionary history of the different tetrapod lineages, at least once, but likely multiple times independently - among them also the lineage leading to mammals.’
The researchers said their findings are surprising and could also be of interest for biomedical studies aiming to unravel the mechanisms responsible for salamander regeneration.
They indicate not only salamander-specific factors may play a role for the high regenerative capacities but also mechanisms that all land vertebrates carry within them due to their common evolutionary heritage.
Different amphibian groups of the Carboniferous and Permian periods around 300 million years ago were able to regenerate their legs and tails in a way previously exclusively known from modern salamanders, the study shows.
Dr Jennifer Olori, of the State University of New York, said: ‘We were able to show salamander-like regenerative capacities in both fossil groups that develop their limbs like the majority of modern four-legged vertebrates, as well in groups with the reversed pattern of limb development seen in modern salamanders.’
The fossils used in the study came from the Berlin Natural History Museum’s collections, as well as others.
Dr Frobisch added: ‘The fossil record shows the form of limb development of modern salamanders and the high regenerative capacities are not something salamander-specific - but instead were much more wide spread and may even represent the primitive condition for all four-legged vertebrates.’
Scientists found the same methods of regeneration were in relatives of modern salamanders (stock image). This implies features were present 80 million years before the first salamanders in the fossil record