Trizocarcinus tacitus Chace, 1940

Trizocarcinus tacitus Chace, 1940 View in CoL

( Figs. 1 – 3 View Figure 1 View Figure 2 View Figure 3 )

Goneplax tridentata — Boone, 1927: 10, figs. 2–4 [ Belize]; 1930: 194, pl. 66, fig. A [Florida] [not Trapezioplax tridentata (A. Milne-Edwards, 1880) View in CoL ; Pseudorhombilidae View in CoL ].

Trizocarcinus tacitus Chace, 1940: 41 View in CoL , figs. 15, 16. — Chace, 1956: 20 [Gulf of Mexico]. — Guinot, 1969: 518, 522 [discussion], figs. 34, 43, 45, 50, 51 [holotype]. — Guinot, 1971: 1081 [in list]. — Soto, 1985: 484, 495. — Soto, 1986: 3, 4, 36. — Soto, 1991: 626, 627. — McLaughlin et al., 2005: 257 [in list]. — Ng et al. 2008: 78 [in list]. — Castro and Ng, 2010: 110 View Cited Treatment , figs. 45A–B, 46 G–M.

Material examined. 4 males (cl: 1.8–3.3 cm, cw: 2.1–3.5 cm), station - MT#63 , 04°36.2400’S 036°45.7395’W, 416 m GoogleMaps , temperature 7.47 °C, salinity 34.6, date: 05 Aug 2011, MOUFPE 18877 View Materials .

Distribution. Western Atlantic: United States (Florida, Dry Tortugas, St. Vincent), Bahamas, Gulf of Mexico, West Indies, Guadalupe, Barbados, Brazil: Rio Grande do Norte (Potiguar Basin) ( Fig. 3 View Figure 3 ), 187– 462 m depth (new record) ( Chace, 1940; Castro and Ng, 2010; herein).

Remarks. The present specimens of T. tacitus agree very well with the original description provided by Chace (1940) and subsequently revised by Castro and Ng (2010); their specimens from the Gulf of Mexico and Caribbean Sea. Trizocarcinus tacitus can easily be distinguished from its congener T. dentatus , which is from Tropical Eastern Pacific, by the following characteristics (in parentheses for T. dentatus ): carapace with dorsal and ventral margin smooth ( Fig. 1A View Figure 1 ) (vs. granular); outer orbital tooth conspicuous and well developed ( Fig. 1A View Figure 1 ) (vs. outer orbital tooth reduced); stridulating ridge absent on pterygostomial region ( Fig. 1B, C View Figure 1 )(vs. granular stridulating ridge on pterygostomial region); ambulatory propodus and dactylus with anterior margin densely setose ( Fig. 1D View Figure 1 ) (vs. structure densely setose along entire length); and G1 apex not particularly long ( Fig. 2A, B View Figure 2 ) (vs. G1 apex prominently elongate) (cf. Castro and Ng, 2010). Trizocarcinus has long being considered as an endemic of the Gulf of Mexico and Caribbean Sea ( Chace, 1940). As observed in this paper, we reported the first occurrence of T. tacitus from Potiguar Basin (Brazilian waters) in the South Atlantic. This is a significant range extension of about 3000 km from its previous range. Trizocarcinus tacitus is probably more abundant and widely spread than is documented here along the Brazilian coast. The general lack of sampling on the upper continental slope in the Southwestern Atlantic will therefore need to be addressed in the future. As previously discussed by Mantelatto et al. (2018), the reasons for the increasing new records and/ or extension of distributions reported for decapod species in Brazilian waters during the last decade are almost certainly related to the increase in larger research programs with laboratories more focused on marine biodiversity. In this sense, we argue in favor of continuity and new investments in biodiversity research programs in order to increase the knowledge of the biota of less explored regions.