 Archaeomarasmius is an extinct genus of gilled fungus in the Agaricales family Tricholomataceae , containing the single species Archaeomarasmius leggetti . It is known from two fruit bodies recovered from amber , one consisting of a complete cap with a broken stem , the other consisting of a fragment of a cap . The cap has a diameter ranging from 3 @.@ 2 to 6 mm ( 0 @.@ 13 to 0 @.@ 24 in ) , while the stem is 0 @.@ 5 mm ( 0 @.@ 02 in ) thick . Spores were also recovered from the amber , and are broadly ellipsoid to egg @-@ shaped , measuring roughly 7 @.@ 3 by 4 @.@ 7 μm . The species , which resembles the extant genera Marasmius and Marasmiellus , is inferred to have been saprobic on plant litter or other forest debris . 
