Trilasma tropicum, Shear, William A., 2010

Shear, William A., 2010, New species and records of ortholasmatine harvestmen from Mexico, Honduras, and the western United States (Opiliones, Nemastomatidae, Ortholasmatinae), ZooKeys 52, pp. 9-46 : 36-37

Trilasma tropicum sp. n. Figs 1928, 2938, 394954, 55

Types.

Male holotype and female paratype from "Las Ventas, Honduras," collected 11 February 1939 by R. V. Chamberlin (AMNH).

Diagnosis.

The short, relatively crassate legs and the extremely prominent subocular keels (Fig. 55) separate this species from others. Trilasma ranchonuevo sp. n. (Tamaulipas, México) has false articulations in femora 2 and 4 that are absent in Trilasma tropicum sp. n. The male has an acute dorsal knob on the basal article of the chelicerae, as well as the tooth on the second article.

Etymology.

The species epithet refers to the occurrence of the species in the Neotropics.

Description.

Male holotype: total length, 2.5, width, 1.4. Color uniform light chestnut brown, metatarsi and tarsi of legs 3, 4 whitish yellow. Nonsexual characters as in female (see Figs 54, 55, and description, below), but dorsal ornament reduced, partially obscured in holotype by secretion; median hood process 0.80 long, 0.3 wide. Scute 1.4 long, 1.4 wide.

Chelicera (Fig. 19) without gland on basal article but with dorsal, conical protuberance, second article with forward-projecting tooth, basal article 0.50 long, 0.21 wide; distal article 0.55 long, 0.19 wide. Palpal patellae and tibiae swollen, epigamic glands probably present but not marked by patches of fine setae (Fig. 29), dimensions of palpus given in Table 11. Legs in order of length, 2 (6.44), 4 (5.34), 3 (3.76), 1 (3.80); legs lacking false articulations; tarsi 1-4 with 5, 5, 6, 7 articles respectively. Lengths of leg segments given in Table 11. Length/width ratios of femora, in order: 4.5, 10.7, 4.2, 7.8.

Genital operculum broadly rounded, marginate, with two small, lateral notches. Penis typical (Figs 38, 39).

Female paratype: The female paratype (Figs 54, 55) is mounted on a SEM stub, therefore it was not possible to get accurate measurements of the appendages. Total length, 2.9, width, 1.8. Carapace arcuate, about twice as wide as long, with complete lateral and posterior submarginal keels; pair of median keels connect eye tubercle and innermost lateral hood process, lateral keels also arising on innermost lateral hood process. Two blunt lateral hood processes each about one-fourth as long as median hood process. Circumocular keels prominent, subocular portion strongly developed, eyes of usual size. Median hood process arising rostrally on eye tubercle, relatively narrow, length 0.8, width 0.3, ten fenestrations on each side, sides nearly parallel; median keels of carapace continue as rows of reduced lateral tubercles on median hood process, about 20-22 lateral tubercles, linearly connected; about 8 dorsal tubercles present, connected to each other but not to lateral tubercles. Metapeltidium free, complete keel along anterior margin, 10 tubercles posterior to keel, connected to it by single branch each. Scute 1.7 long, 1.7 wide. All keels relatively low. Small keel cells of scute area 1 present, small keel cell rows progressively wider posteriorly, widest on area 4; small cells of area 5 few, in two small groups near midline. Paired median scute spines moderately developed, on areas 4 distinctly larger than adjacent keel tubercles.

Chelicerae as described for male, but lacking dorsal protuberance on basal article, tooth on second article. Palpus (Fig. 28) as in male but patellae and tibiae not swollen. Legs in order of length, 2, 4, 3, 1; leg articles without false articulations. Leg femora with typical ornamentation.

Genital operculum broadly rounded, marginate, with suture.

Notes.

I mounted the only female on an SEM stub under the impression there was a second female in the collection, but the second specimen turned out to be a male. Thus measurements of the appendages of the female became impossible, but there is no reason not to suspect that the typical sexual dimorphism in appendage lengths is characteristic of this species.

Las Ventas is not listed for Honduras by the U. S. Board on Geographical Names (http://geonames.nga.mil/ggmagaz), nor could it be found by Google Earth. There are four places named Las Ventanas and one called Las Ventanillas, scattered in four different departments of Honduras. There is a village of Las Ventas in El Salvador (13°35'58.55N; 88°21'00W; 365 m (1050') asl) but it is in the central part of the country, not close to the border with Honduras. Otherwise the name evidently is not used for a populated place in Central America. The type locality is therefore in doubt, but because the collection was made 70 years ago, it is possible "Las Ventas" was in existence then in Honduras, having since disappeared from geographic databases, or the label is a lapsus for one of the Las Ventanas. In any case, if this species is really from Honduras, it occurs farther south than any New World dyspnoan, at approximately the same latitude as Cladolasma angka in Thailand.