A comparative study of fossil leaves of Tomaxellia biforme Archangelsky, 1966, which belong to the family Cheirolepidiaceae, and those of Athrotaxis ungeri (Halle) Archangelsky, 1963, Sequoia sempervirens (D. Don) Endlicher and Taxodium mucronatum Tenore, fossil and extant species, respectively, included within the family Taxodiaceae is presented, using light microscopy (LM) and scanning and transmission electron microscopy (SEM and TEM). The fossil materials occur in the Baquero Formation (Lower Cretaceous), Santa Cruz Province, Argentina. The morphological, anatomical and ultrastructural analyses indicate great similarities between the Cheirolepidiaceae and Taxodiaceae leaves.