![]() Like bears and anteaters, they had the ability to stand on their hind legs, making them the largest bipedal mammals to have existed. These ancient ancestors of modern-day sloths truly lived up their name. Read more: Five-ton giant ground sloth lived in Costa Rica 7 million years ago.Although seemingly powerless against modern tree-dwellers these spikes likely served as a vital protection against the large herbivores of the Pleistocene./Images: Seed pods and thorns of the honey locust tree (Gleditsia triacanthos). Now a popular city tree due to their ability to withstand poor conditions, modern versions of honey locust trees have been bred without spikes although their supersized seed pods still litter our bustling city streets. They also have big, intimidating spikes on their trunks which likely served as an important defense against these giant herbivores. For example, honey locust trees (Gleditsia triacanthos) have large sweet-smelling seed pods that were eaten by megafauna. Only extra-large herbivores such as the giant ground sloths had the ability to swallow avocado seeds whole, meaning that they could carry them around in their digestive tracts and eventually defecate them far away from the parent tree!Įvidence of these ancient symbiotic (mutualistic) relationships can still be seen today. Many plants, especially in tropical ecosystems, have evolved to rely upon animals to spread their seeds. The three skeletons might thus represent a family unit of a mother and two of her offspring.ĭale Gnidovec is curator of the Orton Geological Museum at Ohio State University.Love avocados? Thank the giant ground sloths!ĭid you know that we can thank giant ground sloths for the avocados we have today? Giant ground sloths were one of the few ancient herbivores large enough to swallow avocados whole, thus serving as an important seed disperser for these delicious fruits that we know and love today! Illustration of the giant ground sloths by Robert Bruce Horsfall/Source: Wikimedia Commons Among modern sloths the female is the sole caregiver of youngsters, and large size would have been an advantage in fending off predators. The large size of the Tarkio adult might indicate it was a female. ![]() ![]() In some marine mammals, some primates, some large carnivores, and in tree sloths, the females are larger. In mammals, the males are usually larger, but not always. Given those estimates, the youngster may have been around three years old and the subadult was around 6. Given those values, the lifespan of Megalonyx was probably around 19 years, gestation time 14 months, and sexual maturation occurred at around 6.5 years. In general, body size in mammals correlates well with lifespan, gestation, birth interval and age at sexual maturity. The juvenile, represented only by both shoulder blades, was about 30% the size of the adult. The subadult, represented by about 25% of the skeleton, is half the adult size. It is one of the largest individuals known for the species, with an estimated weight of 2,830 pounds. The bones were exposed for a while before becoming buried, as shown by the weathering, a few rodent gnaw marks, and crushing due to trampling.Ībout half the bones of the adult skeleton were present. The only other bones found at the site were shell fragments of a soft-shelled turtle, a snapping turtle and a pond turtle. The animals most likely died and were buried together, not washed together by chance. Pollen and other plant fossils indicate the area they lived in was along a stream in an open woodland forest, with marshy areas nearby. The animals were alive around 106,000 years ago, during an interglacial, a time when the glaciers had retreated far to the north and the climate was similar to what it is there today. What is even better, they are from an adult, a subadult and a youngster. The site is unique in having three individuals preserved together. Recent analysis of a site in southwestern Iowa, the Tarkio site, has provided some fascinating new insights on the species. The species appeared around 300,000 years ago and became extinct around 11,000 years ago, so it lived through multiple advances and retreats of the glaciers. Since then, remains of Megalonyx have been found at more than 180 sites in North America, from the east to the west coast and from Alaska to central Mexico.
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