phytotaxa - Magnolia Press

Taxonomic notes:—Desmoncus giganteus is characterized by its large size and unusually large fruits
with long fruiting corollas. It is the only species of Desmoncus always reported to have solitary stems; all
other species have clustered or rarely solitary stems. It is probably more common than the few specimens
suggest.
Moreno Suárez and Moreno Suárez (2006) consider that this species occurs in Bolivia. However, the
description and illustrations they give of the fruits do not match those of D. giganteus, and appear more like
those of the large morphotype of D. polyacanthos.
5. Desmoncus horridus Splitg. ex Martius (1844: 51).
Atitara horrida (Splitg. ex Martius) Kuntze (1891: 727). Type:—SURINAME. Paramaribo, no date, F. Splitgerber 61
(holotype BR, n.v., holotype image!).
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.
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