A new genus and species of slime mold, Adeloecnomus palaeus gen. et sp nov., (Myxomycetes) is described from mid-Cretaceous Burmese amber. The somatic plasmodial stage as well as several reproductive fructification stages are present in this species. Diagnostic characters of the reproductive stage are the sessile sporangia, a distinct columella, a peridium that becomes evanescent as the spores mature, dark, irregular-shaped spores and the absence of a stalk and capillitium.