Stenorhynchinae Dana, 1851

Guinot, Danièle & Bakel, Barry Van, 2020, Extraordinary majoid crabs: the genus Esopus A. Milne-Edwards, 1875 in the new subfamily Esopinae subfam. nov., and erection of Paulitinae subfam. nov. (Crustacea, Decapoda, Brachyura, Majoidea, Inachoididae Dana, 1851), Zootaxa 4766 (1), pp. 101-127 : 118-119

Subfamily Stenorhynchinae Dana, 1851

Stenorhynchinae Dana, 1851: 432 ; 1852: 83.

Stenorhynchinae Guinot 2012: 32 .— Števčić 2013: 185. — Davie et al. 2015b: 949; 2015c: 1093. — Bezerra & Pachelle 2016: 212.— Carmona-Suárez & Poupin 2016: 366.

Type genus. Stenorhynchus Lamarck, 1815 [type species by designation by Rathbun (1897): Cancer seticornis Herbst, 1788 ].

Description. Carapace longer than broad, narrow, not sculpted, smooth, naked or minutely pubescent. Rostrum unpaired, very long, longer than carapace, very slender, with spinous margins. Orbits completely absent; only small postocular spine, distant from unprotected eye, situated along long ‘neck’. Basal article of antenna slender, convex ventrally, not longitudinally sulcate; flagellum concealed beneath rostrum. Orbits not defined. Postorbital spine small. Proepistome not completely reaching short epistomial process. Epistome very large. Pleurites 5–8 exposed but relatively small (particularly pleurite 5), forming narrow, smooth, interrupted collar, never expanded nor salient. Carapace partially resting on weak setting gutter. First pleonal somite encroaching on concave posterior carapace margin; first, second pleonal somites integrated into cephalothorax of males; in adult females pleonal somites 1–4, portion of 5 in prolongation of carapace, dorsally visible. Thoracic sternal suture 3/4 only weakly visible laterally, not marked by deep depression. Sternum/pterygostome junction complete. Sternal extensions from P1–P4 connecting to sternum. Chelipeds long, narrow, cylindrical. P2–P5 long, spinous ( Hendrickx 1999: fig. 26B: S. debilis ). Male pleon with 6 somites (pleotelson); first and seemingly second somites integrated into cephalothorax; female pleon with 5 somites, somites 1–4 and a portion of somite 5 in the prolongation of the carapace, visible dorsally. Male gonopore at extremity of coxo-sternal condyle ( Guinot 2012; Guinot et al. 2013: fig. 31D). G1 with lobe and aperture subdistal, with setae ( Brocchi 1875: pl. 19, fig. 17; Monod 1956: fig. 839; Garth 1958: pl. B, fig. 7; Williams 1984: fig. 241o).

Other included genera. None.

Remarks. Stenorhynchus occupies a quite distinct position among the Inachoididae and therefore deserves a special status in the family ( Guinot 2012: 31; Guinot et al. 2013: 225). The exposed pleurites do not show the continuous collar as in other inachoidids, the exposed pleurites appearing more as sclerites as in Inachidae . The expansion of the pleurites seems already present in the first crab stage of S. seticornis ( Yang 1976: fig. 7A). Complete larval development of S. lanceolatus has shown affinities with other inachoidids as well as its separate status ( Paula & Cartaxana 1991), justifying the erection of its own subfamily. According to Marques & Pohle (2003: 77) larval evidence revealed that Stenorhynchus nested basal to Inachoididae . Stenorhynchinae is the only inachoidid representative occurring outside the Western Hemisphere, namely S. lanceolatus , the ‘eastern Atlantic arrow crab’, that is found in the eastern Atlantic (Madeira, Canary Is., Cape Verde Is., and numerous west-African localities from Western Sahara to Angola) ( Capart 1951: 81, fig. 25; Monod 1956: 567, figs. 838, 839; Manning & Holthuis 1981: 304, fig. 78b). Species of Stenorhynchus are for most not decorator crabs and display a peculiar behaviour ( Guinot & Wicksten 2015: fig. 71.11.6G). Molecular sequences obtained from 42 larvae of Stenorhynchus seticornis are deposited in GenBank ( Brandão et al. 2016).

The family Inachoididae did not invade areas outside the Americas and did not radiate in the Old World, except S. lanceolatus .