Desmoncus horridus Splitg. ex Mart., Voy. Amér. Mér. 7(3): 51 (1844)

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Distribution

Map uses TDWG level 3 distributions (http://www.nhm.ac.uk/hosted_sites/tdwg/geogrphy.html)
Boliviapresent (Henderson, A., A revision of Desmoncus (Arecaceae) in Phytotaxa 35. 2011)A
Brazil Northpresent (Henderson, A., A revision of Desmoncus (Arecaceae) in Phytotaxa 35. 2011)A
Brazil West-Centralpresent (Henderson, A., A revision of Desmoncus (Arecaceae) in Phytotaxa 35. 2011)A
Colombiapresent (Henderson, A., A revision of Desmoncus (Arecaceae) in Phytotaxa 35. 2011)A
Ecuadorpresent (Henderson, A., A revision of Desmoncus (Arecaceae) in Phytotaxa 35. 2011)A
French Guianapresent (Henderson, A., A revision of Desmoncus (Arecaceae) in Phytotaxa 35. 2011)A
Guyanapresent (Henderson, A., A revision of Desmoncus (Arecaceae) in Phytotaxa 35. 2011)A
Surinamepresent (Henderson, A., A revision of Desmoncus (Arecaceae) in Phytotaxa 35. 2011)A
Trinidad-Tobagopresent (Henderson, A., A revision of Desmoncus (Arecaceae) in Phytotaxa 35. 2011)A
Venezuelapresent (Henderson, A., A revision of Desmoncus (Arecaceae) in Phytotaxa 35. 2011)A

Discussion

  • Taxonomic notes:-Specimens included in this species were placed by both Wessels Boer (1965) and Henderson (1995) within a widespread Desmoncus orthacanthos Martius. This is a mistake, and the two species are quite distinct, especially in their fruits. The specimen from W illustrated in Dahlgren (1959, plate 186) is not the type of D. horridus, and is anyway now destroyed.
    Subspecific variation:-There is geographic disjunction and specimens occur in five regions-a coastal region stretching from Tobago and Trinidad southeast through the Guianas to Brazil (Maranhão, Pará, Tocantins); an Orinoco region comprising the Orinoco river and its tributaries north and west of the Guayana Highland in Venezuela and reaching adjacent Colombia; an upper Rio Negro region, along the river and its main tributaries in Brazil and adjacent Venezuela and Colombia; a Pantanal region in Brazil and adjacent Bolivia; and a western Amazon region in Ecuador and Brazil (Acre). For most variables there are too few data to test for differences amongst these different regions. However, ANOVA shows that for pair wise comparison probabilities, seven variables (rachis length, basal pinna width, peduncular bract length, peduncle width, rachilla length, number of rachillae, fruit length) differ significantly (P <0.05) between at least one pair of regions, although no variable differs amongst all five regions. Based on these results, specimens from the five regions are recognized as subspecies (subspp. apureanus, horridus, occidentalis, palustris, prostratus). (Henderson, A., A revision of Desmoncus (Arecaceae) in Phytotaxa 35. 2011)A

Description

  • Plants 6.7(2.0-15.0) m tall; stems 2.4(1.2-4.8) cm diameter, clustered. Leaf petioles 4.6(2.0-11.5) cm long; rachises 123.8(32.0-220.0) cm long, 9.5(3.4-20.5) mm wide, the spines usually >1 cm long, mostly adaxial or lateral, straight with briefly swollen bases; pinnae 19(7-28) per side of rachis, without a beard of spines at the bases, without spinules or dense tomentum at the bases adaxially; basal pinna 21.6(12.0-34.0) cm long, 1.9(1.3-3.7) 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 6.4(2.3-13.1) mm wide; peduncular bracts 28.3(10.5-47.0) cm long, 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(7-33), brown tomentose initially; proximal rachillae 10.8(5.0-17.5) cm long, 1.3(0.7-1.9) mm wide; stamens 6-7; fruits 15.4(10.6-21.1) mm long, 9.5(7.4-12.4) mm wide, the surfaces uneven with numerous, subepidermal, short, often branching (Y-shaped) fibers; fruiting corollas less than one quarter as long as fruits, not or scarcely splitting, tending to remain cupular; endocarps narrowly ellipsoid with rounded apices, the pores lateral. (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