Ground sloths are a diverse group of extinct sloths in the mammalian superorder Xenarthra. Ground sloths varied widely in size, with the largest, belonging to genera Megatherium and Eremotherium, being around the size of elephants. Ground sloths are a paraphyletic group, as living tree sloths are thought to have evolved from ground sloth ancestors.
Ground sloth
Fossil Eremotherium skeleton, National Museum of Natural History, Washington, DC.
Paramylodon harlani, Texas Memorial Museum, University of Texas at Austin
A Tamandua anteater in an upright defensive stance similar to those presumed to have been adopted by ground sloths, per trackways preserved in New Mexico
Extinction is the termination of a taxon by the death of its last member. A taxon may become functionally extinct before the death of its last member if it loses the capacity to reproduce and recover. Because a species' potential range may be very large, determining this moment is difficult, and is usually done retrospectively. This difficulty leads to phenomena such as Lazarus taxa, where a species presumed extinct abruptly "reappears" after a period of apparent absence.
Extinction
The thylacine (Thylacinus cynocephalus) is an example of an extinct species.
External mold of the extinct Lepidodendron from the Upper Carboniferous of Ohio
The dodo of Mauritius, shown here in a 1626 illustration by Roelant Savery, is an often-cited example of modern extinction.
