This species grows to a length of 60 centimetres (24 in) SL (for a female specimen) and a maximum weight of 4.6 kilograms (10 lb).

M. uranoscopus occurs in small groups and occasionally forms schools.

This mainly diurnal species inhabits rivers and feeds on the fruits of Licania longipetala and Astrocaryum jauari in addition to pulmonate snails.

This species is not commonly imported but it is appealing for its colour pattern which remains with age.

Diet includes catfish pellets and tablets, prawns and frozen bloodworms.