Well-known to the timber community, ‘Ribbonwood‘ is an attractively grained timber that was extremely restricted in its distribution. The primitive angiosperm Idiospermum australiense, a.k.a. ‘The Green Dinosaur’, is an ever-reliable piece of evidence of rainforest continuity over a period spanning more than 170-million years. It helps to explain why the Daintree Rainforest, on the eastern flank of Thornton Peak (Wundungu), is believed to be the world’s oldest rainforest. Australia’s Wet Tropics harbours refugial pockets of ancient forest, represented with primitive plants that demonstrate an abundance of plants and animals with ancient lineage, dating back to the beginnings of the Jurassic period.
Today, Daintree Rainforest guides visitors through the old-world rainforest into the magnificent Fan Palm (Licuala ramsayi) galleries, to explain its significance and its importance to a planet, which is fast losing its rain forests and therefore its biodiversity, at an alarming rate. Our guides are all rainforest inhabitants. We are still finding new information. Even the green dinosaur is teaching us that our knowledge is fragmentary and that exceptions can disprove the general rules of nature.
The fruit photographed and shown above has nine cotyledons. Until this recent find, we had limited the description of the Dinosaur Tree to having between two and seven cotyledons. Most commonly seen are 3 and 4 segments. Another odd variation was the discovery of Ribbonwood fruit with 2 seeds contained within the single envelope of outer covering, the pericarp. This has been noted from the same tree over two fruitings, this year and last. Lack of symmetry is not uncommon in this primeval forest. Paleo-botanists describe our plants as ‘outlandish’ because the arrangement of leaves on many of the primitive angiosperms does not conform with modern predictable and easily identified families of plants. There is a recognisable structure, but it is unusual.
With the rediscovery of the Idiospermum, it was concluded that the ‘Green Dinosaur’ is one of the most primitive groups of flowering plants on earth, with no other close relatives in the Southern hemisphere. It has extremely high conservation significance among the plants of Australia’s Wet Tropics. Its current distribution is limited to creek catchment areas at the base the three granitic inselbergs in the Wet Tropics section of the Great Dividing Range of Australia. Cooper, Hutchinson, Noah and Oliver Creeks in the closed lowlands rainforests of Thornton Peak, Harvey Creek near Mount Bellenden Ker and Russell River to the south of Mount Bartle Frere are refuges for these plants.
Distinct differences exist between trees in the northern catchments and those in the southern catchments, indicating that an obstruction formed that prevented cross-fertilisation between north and south populations causing speciation which is not yet complete. Most significant is the occurrence of hermaphrodite flowers (having both male and female) features in the south, while in the northern population less than half of the trees are hermaphroditic. The flowers are approximately 35mm in diameter, have hemispherical bracts that open to allow creamy-white petals to show. These petals darken through pale pink, to deeper pink to cerise over two weeks and are seen on the forest floor around June-July, the driest time of the year. Beetles pollenate the flowers, which is appropriate to primitive species that predate more modern families of flying insects.
The value of Daintree Rainforest should not be under-estimated. It is an ecosystem of amazing complexity and intricacy that has survived beyond the life span of other forests. Its unique qualities are emerging through the local inhabitants who have lived in it over sufficient time to be able to note and record features and variations. The role of human inhabitants as responsible caretakers and intergenerational transmitters of values has been interrupted for too long. It’s time for people to acknowledge their responsibility and for governments to remove all obstructions to sustainable living.