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In this episode, we’re zooming in on one of the world’s most diverse and fascinating locales – the island of Madagascar! You may know that Madagascar is home to a variety of fascinating ecosystems today, but the geologic and fossil history of the island is just as exciting!
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Madagascar
The island of Madagascar is home to a wide variety of habitats that host some of the most unique ecosystems on the planet. More than 90% of Madagascar’s animal and plant life is endemic – found nowhere else in the world. Like so many islands, its unusual evolutionary history has allowed certain groups of life to flourish while others remain absent completely.
Some of Madagascar’s exceptional wildlife includes:
-All of the world’s lemurs.
-Two-thirds of the world’s chameleons.
–Spiny forests (an entire unique type of forest!).
-A unique mammalian carnivore – the fossa.
-Tons of endemic reptiles, birds, frogs, fish, insects, plants and so much more
Ancient History
The main reason for Madagascar’s unusual assortment of life is that it has been isolated from all other landmasses for a very, very long time. The island was once part of the supercontinent Gondwana, and later Pangaea. Throughout the Cretaceous Period the continents split apart, and Madagascar finally split off on its own when it broke away from India around 88 million years ago. From that point on, the only living things on the island are either the descendants of very ancient native groups, or descendants of more recent immigrants that rode across the winds and waves.
Not much of Madagascar’s long history is recorded in its fossil record, but a few periods are particularly well-represented.
The Permian-Triassic record of Madagascar provides a variety of mammal ancestors like rhynchosaurs, early dinosaur relatives, ancient amphibians, fish, and plants, and some really neat early reptiles like the gliding Coelurosauravus.
The Late Cretaceous of Madagascar is incredibly rich, mainly in the Maevarano Formation of the Mahajanga Basin. Dating to ~70 million years ago, this fauna existed on the island early in its isolation, and much like the living species, many of these fossil species are unique to Madagascar, including:
-The carnivorous dinosaurs Majungasaurus and Masiakasaurus, plus the titanosaur Rapetosaurus.
-Several ancient crocodyliformes, including the “pug-nosed” Simosuchus.
-Snakes! Including Madtsoia madagascarensis, one of the largest snakes ever at ~8 meters (over 25 feet).
-The perfectly-named “Devil Toad,” Beelzebufo.
–Vintana, a rare “gondwanatherian” Cretaceous mammal.
-Lots more!
The Late Pleistocene / Early Holocene fossil record preserves a number of species that disappeared only within the last few hundreds to thousands of years, painting a picture of a recently-lost ecosystem that included:
-The “sloth lemurs,” a group of lemurs adapted to a life suspended in the trees. These included Archaeoindris, the largest lemur of all time – it was the size of a gorilla!
–Elephant birds! These ratites included Aepyornis, possibly the largest bird ever.
-An extinct croc named Voay robustus.
-Other cool mammals such as a giant fossa and several pygmy hippos!
–Humans arrived on Madagascar as early as 4000 years ago.
More on Madagascar
The World Wildlife Site includes a good overview of the modern-day diversity of the island.
Want to know more about the Late Cretaceous Maevarano Formation? Look to this Scientific American article and this National Geographic interview.
For a couple of more technical overviews of the geologic history of the island and how modern groups of animals and plants made it there, look to Yoder et al 2003 and Samonds et al. 2013. And Burney et al 2004 is a technical overview of those Late Pleistocene-Holocene critters.
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