ULTRASTRUCTURE OF 30-40-MILLION-EAR-OLD LEAFLETS FROM DOMINICAN AMBER(HYMENAEA-PROTERA, FABACEAE, ANGIOSPERMAE)

Hymenaea protera leaflet fossils entombed in amber, dated at 30 to 40 million years (mine strata and exomethylene dating) were observed by b oth light and transmission electron microscopy. Ultrastructure preserv ation in these leaflets shows the presence of chloroplasts with thylak oid membranes, cell walls, mitochondria with associated endoplasmic re ticulum, nuclei, and xylem tissue. Tissues show varying degrees of deg radation; however, natural resin, which has perfused the cells, seems to maintain the structural integrity of the membranes and walls. We co nclude that preservation of amber entombed organisms results from dehy dration and slow fixative properties leaving the ultrastructure in exc ellent condition. These findings parallel reports on the exceptional p reservation of amino acids and of DNA in amber-entombed organisms.