The Lost Pleistocene World of the Seychelles Islands

The Seychelles Island group was part of the southern supercontinent Gondwanaland before the latter broke apart.  It then split away from India 60 million years ago and has been isolated from all continents ever since.  Presently, the Seychelles Islands include separate mountaintops totaling about 282 square miles, but during the last Ice Age it was 1 giant island of about 80,000 square miles…roughly the size of Georgia and half of Florida combined.  Sea level rise has inundated most of the island.

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The Seychelles Islands are located northeast of Madagascar.  They are mountain tops of  a large desert island that existed during Ice Ages.

Map of Seychelles and other islands during the Last Glacial Maximum ~29,000 BP-~15,000 BP.

A human seafarer wrecking his boat on the Pleistocene Seychelles would have discovered both a deserted and a desert island that could have inspired the setting of Robinson Crusoe.  The Seychelles Island was drier with a more sparse tree canopy than is found on the island group today.  A giant species of tortoise (Aldabrachelys gigantea) shaped the landscape into a short grass plain known as “tortoise turf.”  This long lived species (a captive specimen reached the age of 255) still occurs on 1 of the Seychelles atolls.  The Aldabra tortoise creates pathways and selects for shorter species of grasses that grow below its preferred level of foraging.

Primitive amphibians closely related to species found in India occur on the Seychelles.  Caecilians and soogloossid frogs live here.  The presence of these primitive amphibians on India and the Seychelles provides biological evidence that they were once part of the same land mass.

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There are 5 species of caecilians living on the Seychelles.  They are primitive amphibians.

The only dangerous animal for a Pleistocene Robinson Crusoe stranded on the Seychelles would have been the Australian saltwater crocodile (Crocodylus porosus).  Early European explorers reported them as “abundant” on the Seychelles, but they were extirpated here by 1819.  Naturalists wrongly assumed they were African species–either Nile crocodiles or mugger crocodiles.  But a genetic study suggests they were the Australian species.  These saltwater crocodiles occasionally do swim miles into the ocean and surface currents helped carry them to the far away Seychelles.

Saltwater Crocodile | Crocodylus porosus photo

Australian saltwater crocodiles lived on Seychelles until 1819.

At least 238 species of birds live on the Seychelles.  More species than that probably lived on the island before the Indian Ocean submerged most of it.  Sea birds like nesting on islands where few predators roam.  Many species of migratory songbirds get blown off course and learn to survive on islands.  Some evolve into new species.  Pigeons are notorious for getting blown out to sea.  The Seychelles has 5 different species of pigeons.  Settlers wiped out 1 species of parrot (Psitticula wardi) native to the Seychelles.  A fruit-eating bat known as a flying fox is the only native species of mammal on the island group.

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The Seychelles Parakeet is now extinct.

The coc-de-mer coconut palm (Ladoica maldivica) would have provided plenty of food for a stranded Pleistocene Robinson Crusoe.  It produces the largest seed in the world, weighing 50 pounds.  Unlike other coconuts, this species doesn’t float, explaining why it occurs nowhere else.  They produce a toxin that prevents other plants, including competing members of their own species, from growing near its root system.  These slow-growing plants take 800 years to reach full size.

Surviving almost impossible odds – how the Seychelles Coco-de-Mer palm parents its seeds

The coco-de-mer coconut palm is the largest seed in the world, growing to over 50 pounds.

The jellyfish tree (Medusagayune oppostifolia) is a rare species living on the granite mountaintops.  This relic was likely widespread over the Seychelles before the Indian Ocean inundated most of it.

The jellyfish tree is a rare relic that was probably more widespread on Seychelles during Ice Ages.

 

See also: https://markgelbart.wordpress.com/2011/11/11/banana-hole-fossil-sites/

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One Response to “The Lost Pleistocene World of the Seychelles Islands”

  1. Mathieu Says:

    There was also another crocodylian living in Seuchelles: the extinct Aldabrachampsus dilophus.

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