Teramnonotus monodi Santana, 2015, n. gen.

Teramnonotus monodi n. gen., n. sp.

(Figs. 1C–D, 3, 4C, 5C, 6B, D, 7C–D, 8G–I)

Elamena gordonae — Almeida et al. 2007: 29, figs. 7 A–I; Almeida & Coelho 2008: 197; Almeida et al. 2010: 340; Coelho & Coelho Filho 2002: 124; Coelho et al. 2008: 18. [Not Elamena (Trigonoplax) gordonae Monod, 1956]

Type material. Holotype: Brazil: Rio de Janeiro, Baía de Sepetiba, Ponta da Boa Vista, Itacuruçá Island, M. Tavares coll., 4.vii. 1994, dredged from about 15 m on biogenic gravel: ovigerous female, cl. 4.0 mm, cw. 3.5 mm (MZUSP 10272). Paratypes: Brazil: Ceará, Praia do Pecém, L. E. Bezerra coll. 13.x.2010, 1 female (MZUSP 28399). Rio Grande do Norte, Areia Branca, Praia de Baixa Grande, 04°55’44.18”S, 38°30’51.840”W, rocky intertidal, P. Pachelle coll. 29.ix.2011, 1 ovigerous female (MZUSP 29814), 1 ovigerous female, 1 juvenile female (ZRC). Bahia, Baía de Todos os Santos, PROMARLAN, stn CAB1, 12°44’22.920”S, 38°30’51.840”W, i.2005, 1 female, P1–P5 detached from the body (MZUSP 24204). Baía de Todos os Santos, PROMARLAN, stn CAB1, 12°44’22.920”S, 38°30’51.840”W, viii.2004, 1 female, P1–P5 detached from the body (MZUSP 24205). Baía de Todos os Santos, Porto da Barra, 13°00’05”S, 38°32’01”W, 4–6 m, associated with Callyspongia sp. (Porifera), C. Menegola & L. Martins coll. 20.xi.2012, 4 females (MZUSP 29178), 2 females (AM P.97355). Bahia, Baía de Camamu, stn 5, 13º54’14”S, 39º00’34”W, M. C. Cuerrazi coll., 29.viii.2004, 1 ovigerous female (UESC 719). Idem, 25.ix.2004, 1 ovigerous female (UESC 718). Caravelas, Rio Caravelas, stn 1, 17°44’39.4’S, 39°14’49.7”W, A. O. Almeida coll., 28.iii.2007, 1 ovigerous female each (MZUSP 32496, UESC 1090). Bahia, Nova Viçosa, Praia do Pontal da Barra, stn 3, 17°53’00.9”S, 39°21’48.2”W, A. O. Almeida coll., 19.iii.2007, 1 female (UESC 837). Rio de Janeiro, Baía de Sepetiba, Ponta da Boa Vista, Itacuruçá Island, M. Tavares coll., 4.vii. 1994, dredged from about 15 m on biogenic gravel: 2 ovigerous females, cl. 4.3 mm, cw. 3.6 mm and cl. 3.6 mm, cw. 2.8 mm (MZUSP 10273).

Type locality. Brazil, Ponta da Boa Vista, Itacuruçá Island, Baía de Sepetiba, Estado do Rio de Janeiro. About 15 m deep.

Diagnosis. Rostrum well detached from the carapace outline, long, outreached by second antennular article, curved upward, apex sharp. Small tuft of setae on metagastric region. Prominent postocular teeth. Antennules not visible dorsally when folded. Antennular basal article with acute, long anteroexternal tooth. Subhepatic region with 2 lobes, first larger, prominent, second tumescent. Mxp3 exopod nearly reaching distal margin of mxp3 merus. Mxp3 dactylus, propodus of about same length. Teeth of cutting edges of cheliped small, of different sizes. Three pterygostomian lobes.

Description. Carapace pear-shaped, longer than wide, moderately convex; regions undefined, except for poorly marked gastrocardiac groove; dorsal surface with faint longitudinal ridge, with only small tuft of setae on metagastric region. Carapace with discrete anterolateral angle; posterolateral margin slightly angled; posterior margin markedly curved. Narrow, sharp edged rim around carapace, rostrum. Rostrum triangular, short, without subrostral keel, curved upward anteriorly; with minute setae on lateral margin, ventral surface. Cornea visible dorsally. Postocular tooth prominent. Carapace without orbits. Eyestalk immovable, with protuberant anteromesial lobe. Antennules short, stout, not visible dorsally when folded, 3 peduncular articles subequal in length; basal article subquadrangular, with acute anteroexternal tooth; second somewhat longer, more slender than first; distal article thinner. Interantennular septum small. Antenna conspicuously slender, short, concealed by rostrum in dorsal view. Epistome as long as wide. Subhepatic region with 2 lobes; first larger, prominent; second tumescent, undefined. Subtriangular pterygostomian region large, with 3 lobes; first conspicuously prominent, acute; second, third about the same size. Anterolateral angle of the buccal frame projected anteroventrally. Setae absent. Third maxillipeds expopods long, nearly reaching distal margin of merus, with sparse setae on inner margin. Ischium as wide as long, with dense row of stout short setae on inner margin. Merus slightly wider than long, with dense row of long setae on inner margin. Carpus articulating almost centrally between 2 distal merus lobes, setae distally on inner margin. Dactylus, propodus about same length, covered with setae, mostly on inner margin; dactylus fairly stout, bluntly pointed. Inhalant water opening bordered by long setae. Basal portion of epipod strongly curved, single row of long setae traversing anterior edge, separated by suture from lamellar distal portion. Lamellar portion of epipod as long as basal article, slender, fringed with long setae, rounded terminally. Cheliped slender. Ischium long, narrow proximally, with few setae, without projection over merus. Merus long, slender; without spines or tooth, setae sparsely. Carpus short, without projections, few setae. Palm narrower than long, hardly expanded laterally, slightly shorter than merus. Fingers slender, slightly longer than palm, rounded with small gap in proximal third; small teeth of different sizes on both fingers, evenly distributed. Pereiopods similar in size, slightly decreasing in size from P2–P5. Ischium rounded. Merus longer than remaining articles, with long spine on anterodorsal margin. Carpus shorter, without anterior projections, setae sparsely distributed. Dactylus shorter than propodus, curved distally, 2 strong subterminal spines in ventral margin, subequal in size. Propodus, dactylus flattened laterally, with few long setae, sparse short hooked setae. Ventral margin of dactylus with dense row of setae. Female abdomen much wider than long, somites 1, 2 free, somites 3–5 fused, somite 6 separated from previous somites, fused with telson. Row of slender short setae on abdominal margin, setae sparsely distributed on surface. Pleopods 2–5 well developed, projecting laterally beyond abdomen providing greater volume for carrying egg.

Etymology. The present new species is dedicated to the eminent French researcher Théodore André Monod (1902–2000), chercheur d’absolu and professor at the Muséum national d’Histoire naturelle, Paris.

Remarks. Teramnonotus monodi n. gen., n. sp. closely resembles T. gordonae (Monod, 1956) n. comb., from which it can be distinguished in having: (i) both cheliped fingers markedly arcuate and deeply excavated along the mesial surface and spoon-shaped (moderately curved and laterally compressed in T. gordonae), (ii) fingers strongly dentate along the entire length of the cutting margins (Fig. 8 G) (cutting margins edentate in T. gordonae; Fig. 8A), and (iii) the fixed finger of the cheliped ending in a strong bifid tip interlocking with the single, strong tip of dactylus (Fig. 8 G) (no interlocking mechanism, finger distal end inflated, minutely serrate, denticles rounded in T. gordonae; Fig. 8A). The pterygostomial lobe in the new species is also followed by a distinctly smaller lobe continued by a low branchiostegal carina extending backwards to the level of P3/P4 but by a much stronger branchiostegal carina in T. gordonae s. str.

Monod (1956) figured the paratype of T. gordonae as having the merus of both chelipeds ending in a blunt tooth at its inner distal angle (Monod 1956: 471, figs. 632–633), but no tooth is visible in the illustration of the merus of the holotype (Monod 1956: 470, fig. 630). Monod (1956: 472) described the cheliped as being inermis: " Chélipèdes grêles, doigts plus longs que la paume et incurvés transversalement vers l'intérieur, jointifs, inermes ". The merus of the left cheliped of the holotype of T. gordonae s. str. actually ends in a minute tooth, hardly recognizable at its inner distal angle; the right cheliped of the holotype, and the dissected appendages from the paratype are lost. Confirmation of whether the merus of the cheliped is armed with an acute spine will prove to be an additional difference between T. monodi n. sp. and T. gordonae s. str., but it await confirmation by the availability of additional material of T. gordonae (Monod, 1956) s. str. Compared with T. gordonae s. str., T. monodi n. sp. also appears to be larger in size (largest ovigerous females of both species measuring cl 4.0, cw 3.5 mm versus cl 3.1, cw 2.6, respectively).

Teramnonotus monodi n. gen., n. sp. and T. johnlucasi n. gen., n. sp. can be separated from each other by the presence in the former species of: (i) rostrum well detached from the carapace outline, long, outreaching by far the second antennular article, curved upward, apex sharper (Figs. 1C, D; 3A; 4C) (rostrum integrated into the carapace outline, short, not outreaching the second antennular article when fully extended in dorsal view, straight, apex rounded in T. johnlucasi n. gen., n. sp.; Figs. 1A, B; 4B); (ii) a small tuft of setae on metagastric region (Fig. 4C) (setae absent in T. johnlucasi n. gen., n. sp.; Fig. 4B); (iii) prominent postocular teeth (Figs. 1C; 5C) (inconspicuous teeth in T. johnlucasi n. gen., n. sp.; Figs. 1A; 5B); (iv) antennules not visible dorsally when folded (Fig. 5C) (antennules visible dorsally in T. johnlucasi n. gen., n. sp.; Fig. 5B); (v) antennular basal article with acute, long anteroexternal tooth (Fig. 5C) (tooth still distinct but shorter in T. johnlucasi n. gen., n. sp.; (Fig. 5B); (vi) subhepatic region with two lobes, first larger and prominent, second tumescent (Fig. 5C) (both lobes pronounced and of about the same size in T. johnlucasi n. gen., n. sp.; Fig. 5B); (vii) mxp3 exopod nearly reaching the distal margin of the mxp3 merus (exopod reaching distal margin in T. johnlucasi n. gen., n. sp.; Fig. 5B); (viii) mxp3 dactylus and propodus of about the same length (dactylus longer than propodus in T. johnlucasi n. gen., n. sp.); (ix) teeth of cheliped cutting edges small and of different sizes (Fig. 8 G) (teeth of same size in T. johnlucasi n. gen., n. sp.; Fig. 8 D); and (x) three pterygostomian lobes (Fig. 5C) (with two pterygostomian lobes in T. johnlucasi n. gen., n. sp.; Fig. 5B).

Teramnonotus monodi and three other species of hymesomatid crabs are native to the Atlantic Ocean: Halicarcinus planatus (Fabricius, 1775), from Mar del Plata, Argentina southward to Tierra del Fuego, but also from localities outside the Atlantic (Peru, Chile, a number of subantarctic localities and Deception Island, Antarctica) (Melrose 1975: 34; Retamal 1981: 27; Boschi et al. 1992: 64; Boschi & Gavio 2005: 197; Boschi 2000: 84; Davie 2002: 246; Tavares 2004; Aronson et al. 2014); Hymenosoma orbiculare Desmarest, 1823, from Angola, southwest Africa, and South Africa (Monod 1956: 468; Manning & Holthuis 1981: 252); the record from Gabon is questionable (see Capart 1951: 62); and Elamena (Trigonoplax) gordonae Monod, 1956, from two West African localities between Guinea and Liberia.

Two species of hymenosomatids have been recorded from the Western Hemisphere, Neorhynchoplax kempi (Chopra & Das, 1930), a freshwater species introduced into the Panama Canal (Abele 1972) and Elamena mexicana H. Milne Edwards, 1853 (as Elamene mexicana) from Mexico. Henri Milne Edwards (1853: 224) gave no illustration for E. mexicana and provided only an extremely short description: " Carapace plus étroite et à dents marginales plus marquées que dans les espèces précédentes.—Côtes du Mexique ". Milne Edwards probably referred to the Pacific coast of Mexico. The presumed female holotype (by monotypy) of E. mexicana still exists as a dry specimen in the MNHN collections (Fig. 3 B). Judging from this specimen, E. mexicana clearly does not belong in Elamena as now defined (see Ng & Chuang 1996). Because of the general shape of the carapace and appendages, which includes a trilobate rostrum, acute spines on the lateral carapace walls slightly below the carapace edge, approximately dorsal to base of P1 and P2, E. mexicana closely resembles Halicarcinus planatus, whose geographical distribution also includes the Eastern Pacific (Peru and Chile). Elamena mexicana H. Milne Edwards, 1853, is therefore synonymised herein with Halicarcinus planatus (Fabricius, 1775). The geographic distribution given by H. Milne Edwards (1853) for E. mexicana (" Côtes du Mexique ") could have been mistaken, and the specimen was more likely originally obtained from Peru or Chile.

Distribution. Teramnonotus monodi n. gen., n. sp. is known so far from Brazil (Ceará, Rio Grande do Norte, Sergipe, Bahia, and Rio de Janeiro, between about 0 3º S and 22º S).