Ravenea hypoleuca Rakotoarin. & J.Dransf., Kew Bull. 65(2): 300 (2010)

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Distribution

Map uses TDWG level 3 distributions (http://www.nhm.ac.uk/hosted_sites/tdwg/geogrphy.html)
Madagascarpresent (M. Rakotoarinivo & J. Dransfield, New species of Dypsis and Ravenea (Arecaceae) from Madagascar in Kew Bulletin 65. 2010)A
Known only from Vondrozo forest, southeast Madagascar. (M. Rakotoarinivo & J. Dransfield, New species of Dypsis and Ravenea (Arecaceae) from Madagascar in Kew Bulletin 65. 2010)A

Habitat

  • Lowland humid forest, valley bottoms or lower slopes; 550 - 600 m. (M. Rakotoarinivo & J. Dransfield, New species of Dypsis and Ravenea (Arecaceae) from Madagascar in Kew Bulletin 65. 2010)A

Discussion

  • Initially this was confused with Ravenea albicans because of the strongly discolorous leaflets but it differs in the presence of continuous brown scales on the leaf rachis, rather than striped and discontinuous, and the inflorescence branched to 2 orders in the staminate plants. Based on incomplete material, the palm is nevertheless distinct and should be searched for in good fertile state and also elsewhere. The species epithet reflects the discolorous leaflets. (M. Rakotoarinivo & J. Dransfield, New species of Dypsis and Ravenea (Arecaceae) from Madagascar in Kew Bulletin 65. 2010)A

Diagnosis

  • Rakotoarin. & J. Dransf. sp. nov. R. albicanti (Jum.) Beentje affinis sed vagina folii indumento non striato et inflorescentia in 2 ordines ramificanti differt. (M. Rakotoarinivo & J. Dransfield, New species of Dypsis and Ravenea (Arecaceae) from Madagascar in Kew Bulletin 65. 2010)A

Conservation

  • Critically Endangered [CR (B2a+b(iii); D)]. Rare species, known only from Vondrozo where fewer than 20 mature individuals have been seen in an Extent of Occurrence of 6.7 km2. Current threats are mostly related to habitat loss and degradation due to timber extraction. (M. Rakotoarinivo & J. Dransfield, New species of Dypsis and Ravenea (Arecaceae) from Madagascar in Kew Bulletin 65. 2010)A

Description

  • Medium-sized solitary, dioecious palm. Trunk 6 - 10 m tall, 15 -20 cm diam., blackish brown, covered in sheath remnants in the upper part, c. 25 cm in cross section. Leaves 16 -20 in the crown, porrect, marcescent, litter-trapping; sheath 60 - 110 x 10 - 15 cm, pale green, covered in thick white tomentum, margins disintegrating and fibrous; petiole 80 - 150 cm long, 3.5- 4 x 1.5- 2.5 cm in cross section, deeply channelled, margins sharp, covered in white to greyish tomentum; rachis 3.5- 4 m long, in midleaf 2.5- 2.8 ?x 1.8 -2.3 cm in cross section, pale green, covered in thick white tomentum especially on the abaxial surface, keeled on the adaxial surface; leaflets stiff, regularly arranged in one plane, dark green, 52 - 58 on each side of the rachis, proximal leaflets 62- 85 ?x 1.5-2.8 cm, median leaflets 102- 116 x 2.4- 2.8 cm, distal leaflets 16-37- 1.2 - 2 cm, leaflets spaced 4 . 6 cm apart, abaxial surface with continuous white tomentum, transverse veinlets sinuous. Inflorescences interfoliar, solitary. Staminate inflorescence erect, branched to 2 orders; peduncle 24 . 30 cm long, c. 1.5 - 3 cm in cross section, prophyll not seen, peduncular bracts c. 73 cm long, c. 14 cm wide, purplish, covered in thick white tomentum; rachis c. 48 cm long; rachillae 12 - 20 cm long, c. 2 mm in cross section; pedicel 0.6 - 1.2 mm. Flowers not seen. Pistillate inflorescence interfoliar, solitary, erect, branched to 1 order, 20 - 30 cm long, c. 2.4 cm in cross section; prophyll and peduncular bracts not seen; rachis 10 - 17 cm long; first order branches 18 - 22; rachillae 28 - 42 cm long, up to 1 cm in cross section at the base; pedicel 3 - 5 mm high. Flowers not seen. Fruits not seen. (M. Rakotoarinivo & J. Dransfield, New species of Dypsis and Ravenea (Arecaceae) from Madagascar in Kew Bulletin 65. 2010)A

Materials Examined

  • MADAGASCAR. Fianarantsoa, Vondrozo, Madiorano, 22°47'42"S, 47°11'30"E, 22 Oct. 2006, M. Rakotoarinivo 315 (holotype K!; isotype TAN!); idem 22°48'08"S, 47°10'52"E, 4 Sept. 2009, M. Rakotoarinivo et al. 353 (K! TAN!). (M. Rakotoarinivo & J. Dransfield, New species of Dypsis and Ravenea (Arecaceae) from Madagascar in Kew Bulletin 65. 2010)A

Bibliography

A. M. Rakotoarinivo & J. Dransfield, New species of Dypsis and Ravenea (Arecaceae) from Madagascar in Kew Bulletin 65. 2010