Desmoncus osensis Henderson, Phytotaxa 35: 39 (2011)

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Distribution

Map uses TDWG level 3 distributions (http://www.nhm.ac.uk/hosted_sites/tdwg/geogrphy.html)
Costa Ricapresent (Henderson, A., A revision of Desmoncus (Arecaceae) in Phytotaxa 35. 2011)A
From 8°36'-9°31'N and 83°11'-84°06'W in the Osa Peninsula and adjacent areas in Costa Rica at 145(50-350) m elevation in lowland rainforest (Henderson, A., A revision of Desmoncus (Arecaceae) in Phytotaxa 35. 2011)A

Discussion

  • Taxonomic notes:-Desmoncus osensis is similar to D. obovoideus and shares all character states except that D. obovoideus lacks data for stamen number. Desmoncus osensis also has longer and narrower basal pinna compared to D. obovoideus (mean of 23.2 cm long and 3.7 cm wide versus 14.0 cm long and 4.9 cm wide). Based on this, and geographic separation, the two are recognized as separate species.
    Subspecific variation:-Hammel et al. (2003) had only two specimens (Aguilar 290, Morales 6333) available from the Osa Peninsula, and identified them as Desmoncus sp. A. They considered that these two specimens were different from one another and possibly not conspecific. In the present study, seven specimens have been examined. They are indeed variable, and in some the adaxial beard of spines at the bases of the pinnae are poorly-developed. Some of this variation may be due to the age of the leaves represented by the specimens. There is also variation in fruit size. Without more specimens it is not possible to resolve this problem. (Henderson, A., A revision of Desmoncus (Arecaceae) in Phytotaxa 35. 2011)A

Description

  • Plants height no data; stems 1.6(1.2-2.6) cm diameter, branching no data. Leaf petioles 2.7(2.0-3.5) cm long; rachises 85 cm long, 7.1(6.4-7.8) mm wide, the spines usually >1 cm long, mostly adaxial or lateral, straight with briefly swollen bases; pinnae 13 per side of rachis, without long, filiform apices, with an adaxial beard of spines at the bases, without spinules or dense tomentum at the bases adaxially; basal pinna 23.2(18.0-26.0)cm long, 3.7(2.4-5.0) cm wide; cirri well-developed, with acanthophylls, without spines abaxially, with intermediate acanthophylls present, without a wide gap between pinnae and acanthophylls. Inflorescences with the rachis ridged, not twisted, much thicker than the numerous, closely spaced and spirally or irregularly arranged rachillae, each rachilla not or only briefly adnate to the rachis, subtended by an acute bracteole and with a well-developed axillary pulvinus; peduncles 4.5(4.1-4.8) mm wide; peduncular bracts length no data, broad, the surfaces ribbed, brown tomentose, sparsely to densely covered with long, straight or sinuous, briefly swollen-based, diagonally or vertically oriented spines, these flattened or triangular in cross-section, whitish-brown proximally, black or brown distally, with tomentose margins (rarely without spines); rachillae 19(18-19), glabrous or scarcely tomentose initially; proximal rachillae length no data, 1.6 mm wide; stamens 9; fruits 15.1(13.9-17.3) mm long, 13.6(11.0-15.9) mm wide, the surfaces uneven with numerous, subepidermal, long, branching fibers; fruiting corollas less than one quarter as long as fruits, splitting irregularly into 3 lobes, the lobes often splitting again; endocarps broadly obovoid with flattened apices, the pores lateral on or near flattened apices. (Henderson, A., A revision of Desmoncus (Arecaceae) in Phytotaxa 35. 2011)A

Bibliography

    A. Henderson, A., A revision of Desmoncus (Arecaceae) in Phytotaxa 35. 2011