Megalodoras is a genus of thorny catfish in family Doradidae, a South American group named for the bony lateral scutes running the length of the body. The atlas covers two species, M. guayoensis and M. uranoscopus, found across the Amazon and Orinoco drainages in Bolivia, Brazil, Colombia, Ecuador, Peru, and Venezuela. They are large, heavy-bodied bottom fish, running 21–23.5 in in the atlas, with the blunt head, small eyes set high on the skull, and stout barbels typical of big doradids that forage over river-bottom sediment at night.
Megalodoras uranoscopus carries the common name mother of snails catfish, a nod to a diet that leans heavily on freshwater snails and other mollusks crushed with strong pharyngeal tooth plates, a specialization shared by several of the larger doradids. Its size and armored, spine-edged body make it far more a public-aquarium and scientific-collection fish than a home-tank one; when doradids of this scale do appear in the trade they demand a very large system built around their bulk. Both atlas species are assessed as Least Concern.