The timeless swimmer
7/10/13

A group of researchers, led by a young paleontologist from the University of Liege have discovered and studied Malawania anachronus, a fossilized specimen of ichthyosaur, that is more than 100 million years old. What is so particular about this specimen? It belongs to a group of ichthyosaurs that were believed to have been extinct for more than 180 million years. The discovery proves that ichthyosaurs remained diversified for much longer than was previously thought, and challenges theories that have been posited about their extinction. We take a dive with a timeless marine reptile.

A little more than a year ago, Valentin Fischer and his team, at the Department of Geology of the University of Liege, revealed that the Baracromia, a group of ichtyosaurs that appeared during the lower Jurassic, had survived a presumed extinction at the end of the Jurassic, and went on to diversify during the Cretaceous period. (Read The false extinction of ichtyosaurs). They challenged previous theories about the extinction of the ichthyosaur and suggested that a significant part of the group had survived for more than some 50 million years.  

Today, research conducted by this team has enabled them to go a step further and study the characteristics of Malawania anachronus (literally, the out of time swimmer, in Kurdish and Latin), by examining the fossil remains of this ichthyosaur that also lived during the Cretaceous period. To their surprise the researchers discovered that this ichthyosaur belonged to a completely different group which became separated from the Baracromia during an evolutionary radiation dating back to the end of the Triassic (200 million years) and was closer to the species Ichthyosaurus communis. The analysis was published in the journal Biology Letters (1).

Ichtyosaur Malawania
“What this study reveals, is that another group, showing different characteristics than the Baracromia, survived several presumed extinctions of marine species during and at the end of the Jurassic period. Before Malawania was studied, ichthyosaurs of the Cretaceous were believed to be a group that had not greatly diversified, stemming from a single small radiation. Today, we can attest to the fact that there was a much greater diversity of ichthyosaurs during the Cretaceous because 70 million years of evolution separate Malawania from its contemporaries. As a comparison, an equal number of years of evolution separate the whale and the bat”
, explains a delighted Valentin Fischer.

Another striking particularity is the fact that Malawania shows morphological traits that are very similar to its ancestor which is 70 million years older. This reveals a stasis that is unusual for a pelagic reptile. Conversely, its distant cousins the Baracromia, evolved steadily so that they no longer resembled their Jurassic ancestors.

(1)Fischer V, Appleby RM, Naish D, Liston J, Riding JB, et al. (2013) a basal thunnosaurian from Iraq reveals disparate phylogenetic origins for Cretaceous ichthyosaurs. Biology Letters 9: 20130021.

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