Triacanthoneus armatus (Anker, 2010) Anker, 2020

Anker, Arthur, 2020, Taxonomic remarks on the alpheid shrimp genus Triacanthoneus Anker, 2010 with description of a second eastern Pacific species (Malacostraca: Decapoda), Zootaxa 4772 (3), pp. 450-468 : 461-463

Triacanthoneus armatus (Anker, 2010) , comb. nov.

Figs. 7 , 8

Salmoneus armatus Anker 2010b: 181 , figs. 3, 4, 14a.

Material examined. 1 non-ovigerous specimen (cl 3.9 mm), FLMNH UF 51712 , Panama, Bocas del Toro, Isla Colón, STRI Bay, in front of La Cabaña , 9°21’00.8”N 82°15’45.7”W, shallow subtidal muddy flat near mangroves, in burrow between mangrove roots, suction (yabby) pump, leg. P.P.G. Pachelle, 31 March 2019 [PP 19-125] .

Remarks. The specimen from STRI Bay of Isla Colón, Bocas del Toro, is incomplete, missing both of its chelipeds ( Fig. 8 ). Therefore, its identification as T. armatus , based essentially on the armature of the carapace ( Fig. 7 ), must be regarded as somewhat tentative. The position of the mid-dorsal carapacial tooth at about mid-length of the carapace, the presence of sharp postorbital teeth arising directly from the anterolateral margin of the carapace, the absence of a rostral + dorsal carina, and the presence of a small triangular tubercle on the eyestalk, all suggest that this may indeed represent T. armatus .

The morphological resemblance between T. armatus , currently only known from Panama ( Anker 2010b; present study), and T. chapelianus , known from Belize and Cuba (Alvarez et al. 2014; De Grave et al. 2017), requires some attention. As mentioned above, these two species, although being superficially similar, differ in some taxonomically important details. For instance, T. armatus can be separated from T. chapelianus by the presence of a small triangular tubercle on the dorsomesial surface of the eyestalk; such a tubercle is absent in both the Cuban specimen and the holotype of T. chapelianus (Alvarez et al. 2014: fig. 2C). In T. armatus , the carapace does not have a strong mid-dorsal (in fact rostral + mid-dorsal) carina ( Anker 2010b: fig. 3a), which is well marked in T. chapelianus (Alvarez et al. 2014: fig. 2A). In addition, the mid-dorsal carapacial tooth appears to be somewhat more advanced, i.e. in a more anterior position, in T. armatus , compared to T. chapelianus ( Fig. 7 ; Anker 2010b: fig. 3a, b, m; Alvarez et al. 2014: fig. 2A, B; De Grave et al. 2017: fig. 1B). The major chela of T. armatus is somewhat stouter and with proportionally shorter fingers, compared to that of T. chapelianus , whilst the finger cutting edges bear less than 10 irregular bump-like teeth in T. armatus vs. more than 20 minute teeth in T. chapelianus ( Anker 2010b: 4 a–c; Alvarez et al. 2014: fig. 3D). Furthermore, in T. armatus , the third and fourth pereiopod ischia are armed with two robust cuspidate setae ( Anker 2010b: fig. 4g), whilst they are unarmed in T. chapelianus (Alvarez et al. 2014: fig. 4F, G).

Figures

FIGURE 7. Triacanthoneus armatus (Anker, 2010), comb. nov., non-ovigerous specimen (cl 3.9 mm) from Bocas del Toro, Panama (FLMNH UF 51712), anterior portion of carapace and frontal appendages, lateral view.

FIGURE 8. Triacanthoneus armatus (Anker, 2010), comb. nov., non-ovigerous specimen (cl 3.9 mm) from Bocas del Toro, Panama (FLMNH UF 51712); living shrimp (missing both chelipeds) in dorsal [A] and lateral [B] views. Photographs by Paulo P.G. Pachelle.