Mechanisms that lack pollination drops are common in only two groups, Araucariaceae
and some Pinaceae.
The unique aspect of species belonging to the family araucariaceae
is that the orthotropic stems with their bud traces, and the plagiotropic branches with their bud traces, remain permanently orthotropic and plagiotropic, respectively, regardless of any orientation or treatment imposed on them .
It includes 1 genus, Neophyllaphis Takahashi, 1920, currently formed by 13 species specialized in living on Podocarpaceae or Araucariaceae
The species is so old it has been described as a living fossil, with its family - the Araucariaceae
- having been traced to the Mesozoic era, which started 250 million years ago.
The first members of Araucariaceae
, the plant group to which the Wollemi pine belongs, evolved about 200 million years ago, says Murch.
Dubbed "the botanical find of the century" by renowned botanist Ken Hill of the Sydney Botanic Gardens, the tree is a member of the 200-million-year- old Araucariaceae
family, and boasts many unusual characteristics, such as distinctive bark that looks like bubbling chocolate, multiple trunks and deep green fern-like foliage.
Scientists there confirmed it was a new genus of an ancient plant species, called Araucariaceae
, which had existed at the time of dinosaurs.
This appears to have been a more common practice in the case of resins such as Agathis, from the Araucariaceae
family, which is widespread in Insular Southeast Asia, but may also have taken place with Dipterocarpaceae or `dammar' type resins on the mainland (Burkill 1935).
Wood with these features is classified as Araucarioxylon, a very common Triassic-Recent form genus, which bears a close similarity to the woods of the extant conifer family Araucariaceae
Even more remarkable is the fact that it is most closely related to extinct species of Araucariaceae
[a gnus of South American and Australian pines] found in the fossil record in southern Australia about 50 to 150 million years ago.
The Family Araucariaceae
is an extreme case, where 16 studies were restricted to two species.
From this and the evidence of its existence in early groups one can conclude that presence of a pollination drop is ancestral in conifers, but lost from Araucariaceae
and those members of Clade I and II that lack saccate pollen.