Three new phlegmarine-type Lycopodium alkaloids, lycoposerramines-X (2), -Y (3), and -Z (5), having a nitrone residue were isolated from the club moss Lycopodium serratum Thunb. The structures of these new alkaloids, together with the stereostructures of the related alkaloids, huperzines J (1) and K (4), were elucidated by spectroscopic analyses. © 2006 The Japan Institute of Heterocyclic Chemistry.