A new fossil species of Dermestidae (Insecta: Coleoptera), preserved in Late Cretaceous (Turonian) amber from New Jersey, is described as Attagenus (Aethriostoma) turonianensis n. sp. The specimen is fossilized in translucent amber, but 3D imaging using propagation phase-contrast X-ray synchrotron microtomography allowed detailed classification and description. This species is the oldest representative of the subfamily Attageninae and the third fossil species described in the family from the entire Mesozoic. Dermestidae comprise beetle species that typically feed on carcasses, although some Recent species of Attagenus Latreille, 1802 are known to feed on plant debris, which is highly abundant in amber deposit sediments. This new species is evidence for diversification in the family during the Early Cretaceous as well as long morphological conservation of diagnostic features of the genus Attagenus from the Late Cretaceous. Analyzing the taxa from Mesozoic ambers that show stasis, the small size of the specimens together with a specific ecology could explain the stability of these lineages.