Triacanthoneus pacificus Anker 2010
Creators: name: Anker, Arthur
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Alpheidae
Triacanthoneus
Triacanthoneus pacificus

description: Triacanthoneus pacificus Anker, 2010
Figs. 5, 6
Triacanthoneus pacificus Anker 2010a: 54, figs. 5, 6, 10D–F.
Material examined. 1 ovigerous specimen (cl 3.5 mm), FLMNH UF 51710, Panama, Pacific coast, Las Perlas Archipelago, Isla Saboga, small islet in front of Saboga village, 8°37’42.4”N 79°03’24.4”W, rocky-sandy intertidal, under rock on muddy sand, leg. P.P.G. Pachelle & M. Leray, 23 March 2019 [fcn PP19-079]; 1 ovigerous specimen (cl 3.2 mm), OUMNH. ZC. 2014-01-0068, Colombia, Pacific coast, Bahía Málaga, no further data, leg. J.F. Lazarus, July 2009; 1 ovigerous specimen (cl 3.1 mm), OUMNH. ZC. 2016-01-0088, Colombia, Pacific coast, Bahía Málaga, Los Negros, 3°59’N 77°17’W, intertidal, under rocks on sand, leg. A. Anker, 25 April 2009; 1 ovigerous specimen (cl 3.6 mm), OUMNH. ZC. 2016-01-0089, Colombia, Pacific coast, Bahía Málaga, Los Negros, 3°59’N 77°17’W, ARMS placed at 2 m, leg. J.F. Lazarus, 25 April 2009.
Remarks. The present material shows some variation in the position of the lateral carapacial teeth, which can be in the hepatic (well posterior to orbital margin) to post-hepatic position (Fig. 5). In contrast, the position of the middorsal carapacial tooth is relatively stable, between 0.6 and 0.7 of carapace length, although this tooth may slightly vary in size (Fig. 5). All four specimens have a single robust seta in front of the mid-dorsal carapacial tooth (Fig. 5), contrasting to the three robust setae in the above-described T. blanca sp. nov. (Fig. 1B, C). The configuration of the rostrum is also somewhat variable, with the ventral rostral tooth directed ventrally (almost perpendicularly to the main axis of the rostrum) in the holotype (Anker 2010a: fig. 5B, E) and rather ventrolaterally in the present material (Fig. 5). In most specimens, including the holotype, the rostrum is long and more or less horizontal (Fig. 5; see also Anker 2010a: fig. 5B), although in one specimen, the rostrum is noticeably shorter and somewhat descending (Fig. 5B). This is in sharp contrast to the clearly ascending rostrum of T. blanca sp. nov. (Fig. 1B, C), which, however, may be an individual particularity of the single known specimen.
In all four specimens of T. pacificus examined, the antennular stylocerite has a thin longitudinal dorsal lamella or carina, which at its anterior end bears a small, dorsally pointing, subacute tooth (Fig. 5A). Such a tooth was neither mentioned nor illustrated in the original description of T. pacificus (Anker 2010a: fig. 5B), which could be due (1) to the inaccuracy of the drawing, (2) to the slightly different angle of the lateral view of the frontal region, including the right antennule (e.g., slightly more ventral), or (3) to its actual absence or poor development, at least on the right side, in the holotype. Noteworthy, this tooth is much more conspicuous in T. blanca sp. nov. (Fig. 1A, C) and may represent an important synapomorphy of the Pacific clade of Triacanthoneus, which currently includes T. blanca sp. nov. and T. pacificus.
description: Published as part of Anker, Arthur, 2020, Taxonomic remarks on the alpheid shrimp genus Triacanthoneus Anker, 2010 with description of a second eastern Pacific species (Malacostraca: Decapoda), pp. 450-468 in Zootaxa 4772 (3) on pages 460-461, DOI: 10.11646/zootaxa.4772.3.2, http://zenodo.org/record/3819706