Tuesday 15 May 2012

The Dwarf Pachyderms of Crete, Mammoths or Straight-Tusked Elephants?

Fossil Dwarf Elephants are known from a number of small islands around the world; this is not altogether surprising, dwarfism is common in populations of animals cut of on small islands (as is giantism). Animals in such environments often need to adapt to different niches to those they inhabit on larger land-masses, but are able to do so due to lack of competition, since there are few other animals present (conversely in environments with high biodiversity animals tend to be held in their own ecological niche by competition from other species, there is little possibility of switching to other niches, since these are already occupied).

In 1902 adventurer and fossil-hunter Dorothea Bates discovered a number of Elephant Teeth at Cape Malekas on Crete. At the time she assigned these to the genus Palaeoloxodon, Straight-Tusked Elephants, as P. creticus, the Cretan Dwarf Elephant, probably because Dwarf Straight-Tusked Elephants were already known from Sicily and Malta.

The location of Cape Malekas.

Recently this diagnosis has been challenged, and it has been suggested that the Cretan Dwarf Elephant is in fact a Mammoth. Two lines of evidence have been put forward to support this.

Firstly it was suggested that Crete became an island before the arrival of the genus Palaeoloxodon in Europe. However since this wad suggested earlier European members of the genus have been found and the precise date of the deposits in which the Cretan Elephant teeth were found has been questioned, suggesting that they could indeed have reached Crete while it was still attached to the mainland.

Then a genetic study was carried out by a team of scientists led by Nikos Poulakakis of the Natural History Museum of Crete and the Department of Biology at the University of Crete, which suggested that the Cretan teeth had in fact come from Mammoth. However the methodology used in this study was widely questioned, as was the possibility of recovering DNA from remains of this antiquity (about 800 000 years old).

In a paper published in the Proceedings of the Royal Society Series B, Biological Sciences on 9 May 2012, Victoria Herridge and Adrian Lister of the Palaeontology Department at the Natural History Museum in London, carry out a new study of the teeth originally collected by Bates, combined with new material from the same site, based strictly on the morphology of the teeth.

By carefully comparing the Cretan teeth to Palaeoloxodon and Mammoth teeth from the Pliocene and Pleistocene of Europe, as well as Dwarf Palaeoloxodon from Sicily and Malta, and Dwarf Mammoths from Sardinia. This suggested that the Cretan Elephants are in fact a form of Dwarf Mammoth, and should be referred to as Mammuthus creticus.

A pair of molars originally recovered from Cape Malekas by Dorothea Bates in the early twentieth century. Scale bar is 10 cm. Herridge & Lister (2012).

Herridge & Lister the compared the Cretan teeth with those of other known Dwarf Mammoths from around the world; M. lamarmorai from Sardinia, M. exilis from the Californian Channel Islands, and Dwarf forms of M. primigenius from Wrangel Island in Siberia and St Paul Island in Alaska. From this study they concluded that M. creticus was in fact the smallest of all known Mammoths, weighing about 31o kg on average, and standing 1.13 m at the shoulder. This makes it the second smallest Elephant of any sort, with only the Sicilian Dwarf Elephant, P. falconeri, being smaller, with an average weight of 240 kg and a height of 1 m at the shoulder.

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