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2008-11-24 – Eileanchelys waldmani: la prima tartaruga acquatica ? (sea-turtle missing link)

Reperti fossili di un genere di tartaruga ritrovati nel Giurassico scozzese aiutalo a comprendere il passaggio da una vita terrestre ad una marina.

I reperti di Eileanchelys waldmani rappresentano infatti una foma di passaggio in quanto sebbene adattati alla vita acquatica (ritrovati in sedimenti di laguna assieme a squali e altri organismi marini) presentno caratteristiche del cranio tipiche di esemplari terresti.

Inoltre sono comunque molto somiglianti a un genere attuale a prova della “bontà” del progetto evolutivo delle tartarughe acquatiche.


Scottish turtle is missing link

Monday, 24 November 2008
Cosmos Online

LONDON: Turtles normally evoke images of tropical seas, but palaeontologists have found the 164-million-year-old remains of one of the first known water-dwelling turtles on a chilly Scottish island.

These unique fossils bridge what has been a 65-million-year gap in the fossil record primitive land-based turtles and modern turtles, many of which live in the open ocean, said Jérémy Anquetin, based at both University College London (UCL) and the Natural History Museum, in England.

Rugged an beautiful

Against the rugged and beautiful backdrop of the Isle of Skye, his team have unearthed six fossils of a species called Eileanchelys waldmani. The discoveries are described in the British journal the Proceedings of the Royal Society B.

Similar fossils from the Middle Jurassic have been found in the U.S., Argentina, and Russia, but Anquetin’s are the most complete yet discovered and offer new clues about the tricky transition from land to water.

Though it seems an unlikely place to find tropical animals today, “Scotland was much farther south [in the Jurassic]… its position would not have been tropical, but its climate may have been,” said Anquetin.

These turtles would have shared their lagoon and lake environment with sharks and salamanders, whose remains have also been found at the site, he said.

Remarkable similarities

Despite the antiquity of the fossils, the species have some remarkably similar features to turtles found today, particularly a primitive freshwater species called the red-eared slider, found in the southeast of the U.S. and Mexico.

One major difference is that the skull of the fossil is more “reptilian” than modern turtles, said Anquetin. However, the overall body shape, or morphology of these turtles has changed very little over million of years, especially when compared with the transformations seen in mammals.

“I like to think [turtles] are an evolutionary success … because their body plan is still working,” said Anquetin, who added that (like crocodiles) they have outlived many catastrophes including numerous ice ages and mass extinctions.

The exciting research is helping plug a 65 million year gap in the fossil record, commented Walter Joyce a vertebrate palaeontologist and fossil turtle expert at the University of Tuebingen in Germany.

“The new fossil is finally giving us a glimpse of how early turtles evolved,” he said. “The authors make a compelling case that by this stage in evolution turtles had started moving into aquatic habitats.”


Scientific article:

Jérémy Anquetin, Paul M. Barrett, Marc E.H. Jones, Scott Moore-Fay and Susan E. Evans

 The discovery of a new stem turtle from the Middle Jurassic (Bathonian) deposits of the Isle of Skye, Scotland, sheds new light on the early evolutionary history of Testudinata. Eileanchelys waldmani gen. et sp. nov. is known from cranial and postcranial material of several individuals and represents the most complete Middle Jurassic turtle described to date, bridging the morphological gap between basal turtles from the Late Triassic–Early Jurassic and crown-group turtles that diversify during the Late Jurassic. A phylogenetic analysis places the new taxon within the stem group of Testudines (crown-group turtles) and suggests a sister-group relationship between E. waldmani and Heckerochelys romani from the Middle Jurassic of Russia. Moreover, E. waldmani also demonstrates that stem turtles were ecologically diverse, as it may represent the earliest known aquatic turtle.

Additional electronic material (free access) – PDFHTML


novembre 24, 2008 - Posted by | - Rettili, 2 Jurassic / Giurassico, Articolo sc. di riferimento, Europa, Italiano (riassunto), P - Ritrovamenti fossili, Paleontology / Paleontologia | , , , , , , , , , ,

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