Forest bismarckia  (Satranala decussilvae)

Classified as Endangered (EN) on the IUCN Red List (1).

This unusual palm tree was first discovered by the Royal Botanic Gardens, Kew in 1991 and was distinctive enough to be placed in its own genus (2). The leaves are fan-shaped and the genus name Satranala actually means 'fan palm of the forest' in Malagasy (2). This species is a solitary, dioecious tree with a hard, straight trunk supporting around 20 - 24 fan-shaped leaves (4). The most exciting and intriguing feature of this palm however, are the seeds, the inner coat of which carries ridges and flanges that are unique amongst palms in the region, whose seeds are generally smooth (2). These seeds are so unique in fact, that they resemble (albeit faintly) only a few other palm species on the far-off island of New Guinea (2). The species name decussilvae is Latin for 'jewel of the forest' (2).

Endemic to Madagascar, this palm is found at within the Mananara Biosphere Reserve (2), in the northeast of the island (3), and in a few scattered populations in the Masoala National Park (4). It has also been recorded in Pointe à Larée forest, in the district of Soanierana Ivongo (5).

Satranala decussilvae occupies wet rainforest on shallow soils within steep-sided valleys (4), or low ridge tops. Found between 250 and 285 metres above sea level (4).

It has been hypothesised that the unusual ridged seed coat that this palm possesses may have evolved in the same way to the similar adaptation of some New Guinea palms (2). These species have ridged seeds so that they are unharmed when the fruit is eaten, and therefore dispersed, by the flightless cassowary bird. A large, flightless bird also existed on Madagascar until the 17th Century; it was known as the elephant bird (Aepyornis maximus) and may have been more than three metres tall (2). It is possible that the elephant bird, or a now extinct mammal, dispersed the Satranala decussilvae seed in a similar way, and that the bird or mammal was a necessary part of this palm's life cycle (2).

Vast tracts of Malagasy forests have been cleared, predominantly by slash-and-burn agriculture, and much of the former habitat has been lost. There seems very little, if any, effective dispersal of the palm at the present day and this makes it particularly vulnerable (6).

Satranala decussilvae occurs within the Mananara Biosphere Reserve and the Masoala National Park, where it receives a degree of protection (4) (7). Recently, commercial growers have collected large numbers of seeds and seedlings are quite widespread among the collections of palm enthusiasts. It is not known whether the harvesting of seed represents a further threat to the populations (6).