Look at compressed Metasequoia foliage from the Cretaceous of Alaska and at the paper by Serbet and Stockey on cones from Drumheller, Alberta. A fossil family, the Cheirolepidaceae, which may be transitional between the Voltziales and Taxodiaceae is important from the Triassic through the Cretaceous in Europe and Argentina. This family is a good example of the greater degree of conifer diversity that occurred during the Mesozoic. We know this group was widespread and ecologically important because of both the megafossil record and its distinct pollen, Classopollis , which rivals the angiosperms in complexity of pollen wall structure. These plants are monoecious or dioecious trees and shrubs with leaves that are either opposite or whorled and usually scalelike.
Pollen is nonsaccate.
The fossil record of cupressaceous plants is less detailed than for a number of the families discussed above. One problem is that it is difficult to determine whether some foliage is cupressaceous or taxodiaceous based on whether leaves are borne decussately or helically. This family is at least as old as the Jurassic, with extant genera recognizable by the Upper Cretaceous. This family is represented by the genus Cephalotaxus . These plants are mostly dioecious trees or shrubs with spirally arranged to two-ranked, needlelike leaves.