Chemical investigatio n of the Indonesian sponge Lissodendoryx (Acanthodoryx) fibrosa yielded the new 2-aminoimidazole alkaloids lissodendrins A (1) and B (2). Their structures were unambiguously determined by extensive NMR spectroscopic (1H,13C, ROESY and long-range HMBC) studies and mass spectrometric (HRESIMS/MS) data. Lissodendrins A (1) and B (2) possess unprecedented skeletons with the latter compound bearing a (p-hydroxyphenyl)glyoxal moiety, which is rarely encountered in natural products. A plausible biosynthetic pathway for these new metabolites is proposed. Copyright © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim