Teramnonotus johnlucasi, Santana, William, 2015

Santana, William, 2015, A new genus and two new species of hymenosomatid crabs (Crustacea: Brachyura: Hymenosomatidae) from the southwestern Atlantic and eastern Australia, Zootaxa 3905 (1), pp. 91-106 : 94-96

Teramnonotus johnlucasi n. gen., n. sp.

( Figs. 1A–B , 4B , 5B , 6A , 7A–B , 8 D–F)

Elamena gordonae — Lucas 1980: 174, figs. 2B, 6E, Ng & Chuang 1996: 6 [pro parte], Davie 2002: 243, Almeida et al. 2007: 29 [pro parte], Almeida & Coelho 2008: 197 [pro parte], Coelho et al. 2008: 18 [pro parte]. [Not Elamena (Trigonoplax) gordonae Monod, 1956 ]

Type material. Ovigerous female holotype cl. 2.8 mm, cw. 2.7 mm, P1–P5 detached from the body, Australia, Queensland, Tyroom Roads, Gt. Sandy Strait, J. S. Hynd coll., iii.1952, from a spiny alcyonarian from 18 m (10 fms) (AM P.12208); ovigerous female paratype cl. 2.5 mm, cw. 2.4 mm, P1–P5 detached from the body, same data ( MZUSP 32909).

Type locality. Australia, Queensland, Tyroom Roads, Gt. Sandy Strait, 18 m.

Diagnosis. Rostrum integrated into carapace outline, short, not outreaching second antennular article when fully extended in dorsal view, apex rounded. Tuft of setae on metagastric region of carapace absent. Inconspicuous postocular teeth. Antennules visible dorsally when folded. Antennular basal article with distinct but short anteroexternal tooth. Subhepatic region with 2 pronounced lobes of about same size. Mxp3 exopod nearly reaching distal margin of mxp3 merus. Mxp3 dactylus longer than propodus. Teeth of cutting edges of cheliped small, equal. Two pterygostomian lobes.

Description. Carapace pear-shaped, longer than wide, slightly convex; regions undefined, except for poorly marked gastrocardiac groove; dorsal surface with faint longitudinal ridge, without setae. Carapace anterolateral, posterolateral angles almost imperceptible, posterior margin rounded. Narrow sharp edged rim around carapace, rostrum. Rostrum straight, directed forward, broadly triangular, short, without subrostral keel; with minute setae on lateral margin, ventral surface. Cornea visible dorsally. Postocular tooth short. Carapace without orbits. Eyestalk immovable, with protuberant anteromesial lobe. Antennules short, stout, visible dorsally when folded, 3 peduncular articles subequal in length; basal article subquadrangular, with acute anteroexternal tooth; second somewhat longer, slender than first; distal article thinner. Interantennular septum small. Antenna very slender, short, concealed by rostrum in dorsal view. Epistome as long as wide. Subhepatic region with 2 marked lobes of approximately same size. Subtriangular pterygostomian region large, with 2 lobes; first prominent, acute, second smaller. Anterolateral angle of buccal frame projected anteroventrally. Setae absent.

Mxp3 exopod long, 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, heart-shaped, with dense row of long setae on inner margin. Carpus articulating almost on lateral lobe of merus, with setae distally on inner margin. Dactylus longer than propodus; dactylus, propodus 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.

P1 slender. Ischium short, narrow proximally, with few setae, without projection over merus. Merus long, slender, without spines or tooth, sparsely setous. Carpus short, without projections, with few setae. Palm narrower than long, hardly expanded laterally, vaguely shorter than merus. Fingers slender, slightly longer than palm, rounded, with very small gap in proximal third; small, equal teeth on both fingers, evenly distributed. Pereiopods similar, slightly decreasing in size from P2–P5. Ischium rounded. Merus with long spine on anterodorsal margin, longer than remaining articles, with few setae. Carpus shorter, without anterior projections, sparsely setate. Dactylus shorter than propodus, curved distally, 2 strong subterminal spines almost of same size on ventral margin. Propodus, dactylus flattened laterally, with few long setae, sparse short hooked setae. Ventral margin of dactylus with row of setae. Female abdomen much wider than long, somites 1, 2 free, somites 3–5 fused, somite 6 separate from previous somites, fused with telson. Abdominal margins with short setae; setae sparsely distributed over abdominal surface. Pleopods 2–5 well developed, projecting laterally beyond abdomen providing greater volume for carrying eggs.

Etymology. The new species is named for John S. Lucas (James Cook University, Townsville, Australia) in recognition of his contributions to the knowledge of hymenosomatid crabs.

Remarks. The two ovigerous females from eastern Australia that form the basis for the description of the present new species were formerly considered by Lucas (1980: 174–175) as conspecific with Elamena gordonae Monod, 1956 , from the eastern Atlantic. The type material of E. gordonae was not available at that time for him to compare. A direct comparison between the types of E. gordonae and the Australian specimens has now shown that the Australian material should be assigned to a new species in Teramnonotus n. gen., along with E. gordonae Monod, 1956 (see above). Teramnonotus johnlucasi n. gen., n. sp. can be separated from T. gordonae ( Monod, 1956) n. comb. in having: (i) rostrum integrated into the carapace outline, short, not outreaching the second antennular article when fully extended in dorsal view, apex rounded ( Figs. 1A ; 4B; 5B) (rostrum well detached from the carapace outline, long, outreaching by far the second antennular article, apex sharper in T. gordonae ; Figs. 4A ; 5A); (ii) pterygostomial lobes small, first rounded, second weak ( Fig. 5B ) (pterygostomial lobes distinctly large, first ending in an acute tip, second much smaller but clearly discernible in T. gordonae ); (iii) subhepatic lobes about the same size ( Fig. 5B ) (subhepatic lobes clearly of distinct sizes, first much larger in T. gordonae ); (iv) antennules visible dorsally when folded ( Fig. 5B ) (antennules not visible dorsally in T. gordonae ; Fig. 5A ); and (v) no tuft of setae on metagastric region of the carapace ( Fig. 4B ) (small tuft of setae on metagastric region in T. gordonae ). It also appears that T. johnlucasi is smaller in overall size than T. gordonae , the smallest mature female being only 2.5 mm (cl) (cl. 3.1 mm in T. gordonae ). Lucas (1980: 175) had noticed its minute size: " E. gordonae [presently T. johnlucasi ] is smaller than the other 'triangular' Elamena species, except E. umerata n. sp".

In T. johnlucasi , the P2–P4 dactyli are armed with two subterminal teeth of about the same size. The number of subterminal teeth in the P5 seems variable. Although in the type specimens the P1–P5 are detached from the body, the P5 is readily recognizable because of its smaller size. One of the P5 pairs has only one subterminal tooth, the distal one, whereas the other pair has two subterminal teeth, though the proximal tooth is tiny and hardly recognizable. The examination of additional specimens of T. johnlucasi will be necessary to determine whether the bidentate P5 is another distinctive character between T. johnlucasi and T. gordonae or just variation. It must be noted that Monod (1956) figured the holotype of E. gordonae with tridentate P2–P4, while the P5 lack the subterminal tooth ( Monod 1956: 470, fig. 630). The P5, however, is tridentate in his figure of the paratype ( Monod 1956: 471, fig. 636). Monod (1956: 472) maintained in his description that the P2–P5 are tridentate: " Péréiopodes grêles, avec au bord supéro-distal du mérus une forte saillie tuberculiforme; dactyles 3-dentés (1 apicale + 2 subapicales internes)". Because the left P5 dactylus of the holotype is broken and the right P5 missing, and the dissected appendages from the paratype are also missing, it is not possible to verify if the P5 is bi- or tridentate in E. gordonae s. str.

Distribution. So far known from eastern Australia (Queensland, Tyroom Roads, Gt. Sandy Strait, 18 m deep).

Figures

FIGURE 1. A – D, habitus, dorsal and ventral views. A, B, Teramnonotus johnlucasi n. gen., n. sp., ovigerous female holotype cl. 2.8 mm, cw. 2.7 mm (AM P. 12208). C, D, Teramnonotus monodi n. gen., n. sp., ovigerous female paratype cl. 4.3 mm, cw. 3.6 mm (MZUSP 10273). Note (arrows) rostrum integrated into the carapace outline in A (versus rostrum well detached from the carapace outline in C). A – D, stained with methylene blue. Scale bars: A – D, 1 mm.

FIGURE 4. A – D, habitus, dorsal view. A, Teramnonotus gordonae (Monod, 1956) n. gen., n. comb., holotype (after Monod 1956: fig. 629). B, Teramnonotus johnlucasi n. gen., n. sp., ovigerous female holotype cl. 2.8 mm, cw. 2.7 mm (AM P. 12208). C, Teramnonotus monodi n. gen., n. sp., ovigerous female paratype cl. 4.3 mm, cw. 3.6 mm (MZUSP 10273). D, Elamena mathoei (Desmarest, 1823), female (ZRC 1994.4235). Scales: A – D, 1 mm.

FIGURE 5. A – D, anteroventral view of the cephalothorax. A, Teramnonotus gordonae (Monod, 1956) n. gen., n. comb., holotype (after Monod 1956: fig. 630 bis). B, Teramnonotus johnlucasi n. gen., n. sp., ovigerous female holotype cl. 2.8 mm, cw. 2.7 mm (AM P. 12208). C, Teramnonotus monodi n. gen., n. sp., ovigerous female paratype cl. 4.3 mm, cw. 3.6 mm (MZUSP 10273). D, Elamena mathoei (Desmarest, 1823), female (ZRC 1994.4235). Arrows indicate the rostrum, which is integrated into the carapace outline in B (rostrum well detached from the carapace outline in C). Scales: A – D, 1 mm.

FIGURE 6. A – C, lateroanterior view of carapace. D, F, posterior view of the cephalothorax and abdomen. E, posterodorsal view of cephalothorax. A, Teramnonotus johnlucasi n. gen., n. sp., ovigerous female holotype cl. 2.8 mm, cw. 2.7 mm (AM P. 12208). B, D, Teramnonotus monodi n. gen., n. sp., ovigerous female paratype cl. 4.3 mm, cw. 3.6 mm (MZUSP 10273). C, F, Elamena mathoei (Desmarest, 1823), female (ZRC 1994.4235). E, Trigonoplax unguiformis H. Milne Edwards, 1853, female (RMNH). Arrows indicate the absence of the rostral keel in A – B (distinct vertical keel on ventral surface of rostrum in C). Ab 1, Ab 2, first and second abdominal somites. CxP 5, coxa of the pereopod 5. St 8, thoracic sternite 8 exposed. Scales: A – D, 1 mm. E – F, 2 mm.

FIGURE 7. A, C. Female abdominal somites and pleotelson, dorsal view. A, B, Teramnonotus johnlucasi n. gen., n. sp., ovigerous female holotype cl. 2.8 mm, cw. 2.7 mm (AM P. 12208). C, D, Teramnonotus monodi n. gen., n. sp., ovigerous female paratype cl. 4.3 mm, cw. 3.6 mm (MZUSP 10273). Ab 1, Ab 2, first and second abdominal somites. Ab 3 – Ab 5, third, fourth and fifth abdominal somites fused together. PlT, pleotelson (sixth abdominal somite and telson fused together). Scales: A – D, 1 mm.

FIGURE 8. A – C, Teramnonotus gordonae (Monod, 1956) n. gen., n. comb. A, ovigerous female holotype cl. 3.1 mm, cw. 2.6 mm (MNHN-B 25803). B – C, ovigerous female paratype cl. 2.4 mm, cw. 2.2 mm (MNHN-B 25802) (after Monod 1956: figs. 634 and 636). D – F, Teramnonotus johnlucasi n. gen., n. sp., ovigerous female paratype cl. 2.5 mm, cw. 2.4 mm (MZUSP 32909). G – I, Teramnonotus monodi n. gen., n. sp., ovigerous female paratype cl. 4.3 mm, cw. 3.6 mm (MZUSP 10273). A, D, G, right cheliped, lateral view. B, E, H, right P 2, lateral view. C, F, I, left P 5, lateral view. Scales: 1 mm.