Giant Ground Sloth: Megatherium americanum



Prof Chris Jiggins of the University of Cambridge Department of Zoology writes:

One of the most imposing specimens in the museum is the skeleton of the Giant Ground Sloth, Megatherium americanum. This species was part of a large megafauna in the American tropics, which until around 10,000 years ago may have reached a similar biomass to that of African mammalian herbivores in recent times. I first came across this remarkable megafauna soon after starting my PhD fieldwork in Ecuador, when I read a paper by Dan Janzen and Paul Martin entitled ‘Neotropical Anachronisms: The fruits the Gomphopheres ate’. This highly entertaining paper speculated that many of the adaptations seen in modern neotropical plants, such as giant spines on the trunks of Ceiba trees, might have arisen as a defence against these now-extinct megaherbivores. I spent many long hot days searching for butterflies in Ecuador, and in quiet moments paused to wonder what the landscape would have looked like in the presence of these massive herbivores. Incidentally, the Gomphopheres in the title of Janzen’s paper are a now-extinct group of elephant-like herbivores that would have lived alongside the ground sloths. This in itself is remarkable as the former evolved in North America, while the latter arose in South America, the two only coming together during the Great American Biotic Exchange, when the isthmus of Panama linked north and south and permitted these two great faunas to mix. Perhaps from a fieldwork health and safety perspective, it is better that these giant animals are now extinct, but this was perhaps the earliest mass extinction event caused by humans, and in my mind at least, they are sadly missed.

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