The Araucariaceae: An evolutionary perspective

The Araucariaceae, containing two extant genera, Agathis and Araucaria, is a Southern Hemisphere conifer family with a very resticted present day distribution. Although the group has only a few living species, it was once widespread including numerous taxa in the Northern Hemisphere in the Jurassic Period. Cuticle studies of recent araucarians have led to a better understanding of leaf remains present in the fossil record. The genera Brachyphyllum and Pagiophyllum, often reported as araucarian foliage, may only belong to this family in part. The name Araucarioxylon for wood has often been confused with other genera such as Dadoxylon; and most workers do not base evolutionary studies on woods alone since those of living genera are difficult to distinguish. Agathis occurs as a Southern Hemisphere fossil in the Tertiary. Northern Hemisphere representatives such as Dammarites albens are probably not related. Araucaria extends back into the Jurassic. Reports of Triassic remains such as Primaraucaria remain in doubt. Representatives of the sections Eutacta, Intermedia, Columbea, and Bunya of the genus Araucaria all have fossil representatives, Eutacta and Bunya being the oldest. Well-preserved Bunya section cones from Europe, South America and India suggest that this section was widespread in both hemispheres during the Jurassic, and that the section Bunya be retained in current taxonomic schemes even though it contains only one extant species.