How Much Elephant Is In That Mouse?

‘New mouse species has elephant DNA,’ declared the headlines. It must have been hard to resist, considering the contrast in size between these animals. The wording conjures up images of runt elephants evolving into dwarf and then pocket pachyderms before shrinking so small that they could run up their bigger cousins’ trunks.

To further support the idea, the new species is part of a group called sengis, also known as elephant shrews.

Sadly, it’s all complete rubbish. Macroscelides micus is as closely related to elephants as aardvarks are. Yes, they share genes, but so do all creatures. Go back far enough and every living thing is related.

Part of the confusion arises because of the common name, which was probably given to them because of their long thin snouts.

But their noses are not prehensile like an elephant’s trunk. They’re much more like the long nose of an anteater, and serve the same function, since sengis are also insectivores.

But a bigger part is due to the discoverers’ attempts to clear up another misunderstanding. Elephant shrews used to be considered members of the Soricidae family, to which true shrews belong. But since the 1990s, its been known that they evolved separately.

By the time the dinosaurs became extinct 165 million years ago, the super continent Pangaea had already split in two, forming Laurasia (present day North America, Europe and Asia) and a southern supercontinent called Gondwana, which included Africa. Shrews evolved in Laurasia, while the sengis, the so-called elephant shrews, were among numerous species that evolved in Gondwana.

The apparent similarities between shrews and sengis is called convergent evolution. Another example of this is the way birds and bats both evolved wings, quite separately from each other.

To clarify that M micus is not related to Eurasian shrews, Drs Jack Dumbacher and Galen Rathbun of theCalifornia Academy of Sciences and their colleagues said in their paper for the Journal of Mammalogy that the sengis had ‘distant phylogenetic affinities to elephants, sea cows, hyraxes, aardvarks, golden moles, and tenrecs, which collectively belong to the supercohort Afrotheria.’

Ooops.

The story began with the collection of sengis samples by Michael Griffin of the Namibian Ministry of Environment and Tourism. One of those samples didn’t quite belong with the others. So the three, plus Seth Eiseb of the National Museum of Namibia, set out to look for more examples.

During nine expeditions they found a total of 16 specimens, which they compared to collections in Windhoek, Pretoria, London, Los Angeles and San Francisco to confirm that they had a new species.

“Genetically, Macroscelides micus is very different from other members of the genus,” said Dumbacher, the academy’s curator of ornithology and mammalogy. “It’s exciting to think that there are still areas of the world where even the mammal fauna is unknown and waiting to be explored.”

On average, science discovers a dozen new mammal species a year.

Source: http://www.forbes.com/