Stratiolibinia, S, M A R C O S Tava R E & Santana, William, 2011

S, M A R C O S Tava R E & Santana, William, 2011, A new genus for Libinia rostrata Bell, 1835, with comments on the validity of Libinia bellicosa Oliveira, 1944 (Crustacea, Brachyura, Majoidea, Epialtidae), Zootaxa 3057, pp. 61-68 : 61-64

Stratiolibinia gen. nov.

Type species. Libinia rostrata Bell, 1835 , by present designation. Gender feminine. Included species. Stratiolibinia rostrata ( Bell, 1835) gen. nov., comb. nov., and S. bellicosa ( Oliveira, 1944) gen. nov., comb. nov.

Diagnosis. Carapace subglobose, covered by thick velvet; regions swollen, well distinct, armed with tubercles, spines including: 3 protogastric, 3 mesogastric, 1 metagastric, 1 cardiac, 1 intestinal spines. Pterygostomian, hepatic, proto-, meso-, metabranchial, branchiostegal regions with spines, tubercles; branchiostegal spine longest, laterally directed. Rostrum very broad, ending in widely divergent spines. Preorbital spine strong, acute; postorbital spine cup-like; orbit single notched dorsally. Cheliped long, merus armed with spines, tubercles. Pereiopod 2 almost as long as cheliped, dactylus much shorter than propodus. P3-P5 comparatively short, diminishing progressively in length posteriorly; dactyli corneous tips deeply excavated ventrally, with one (sometimes two) distinct, ventral tubercle behind it. Last thoracic pleurite (ThPl8) extremely reduced. Lower parts of both ThPl8, ThPl7 upturned, swollen, forming low thoracic pleural gutter for channeling of water. Male sterno-abdominal cavity very deep, narrow, not limited laterally by tubercles at the level of thoracic sternites VI–VII, closed anteriorly by strong crest derived from sternite IV. Visible parts of male thoracic sternite VIII small (abdomen removed). Male, female abdomen of six somites and telson. Male abdominal somites 4 and 5 only slightly concave laterally. Male telson tight-fitting into sterno-abdominal cavity, relativelly narrow, distinctly triangular. G1 stout, straight, with bilobed apex, keel well developed, blunt. G2 slender, straight, very short (one fifth the length of G1).

Remarks. Stratiolibinia gen. nov. can be easily distinguished from Libinia Leach, 1815 , by an unique combination of characters, which include: (i) male sterno-abdominal cavity is very deep and narrow ( Fig. 1A ), whereas it is shallower and distinctly wider in Libinia ( Fig. 1C ); (ii) male sterno-abdominal cavity is closed anteriorly by a strong crest on thoracic sternite IV ( Fig. 1A, B ), sterno-abdominal cavity is open anteriorly in Libinia ( Fig. 1C, D ); (iii) male sterno-abdominal cavity is not delimited laterally by tubercles at the level of thoracic sternites VI–VII ( Fig. 1A ), two strong tubercles delimit the sterno-abdominal cavity laterally (lateral swellings) at level of thoracic sternites VI–VII, one tubercle each in Libinia ( Fig. 1D ); (iv) male abdominal somites 5 and 4 are only slightly concave laterally ( Fig. 1B ), abdominal somites 5 and 4 are deeply concave laterally to receive the lateral swellings from thoracic sternites VI–VII in Libinia ( Fig. 1D ); (v) visible part of male thoracic sternite VIII is small (abdomen removed) ( Fig. 1A ), it is distinctly larger in Libinia ( Fig. 1C ); (vi) upturned edge of the thoracic pleural gutter is low (formed by ThPl7 and ThPl8), it is noticeably higher in Libinia ; (vii) P2 dactylus is much shorter than the P2 propodus ( Fig. 3A ), P2 dactylus is about as long as propodus in Libinia ( Fig. 3B ); (viii) P2–P5 dactyli are armed with one (sometimes two) distinct, ventral tubercle behind their corneous tips, whose ventral surface are deeply excavated longitudinally ( Fig. 3 C), the P2–P5 dactyli have no ventral tubercle behind their corneous tips and their corneous tips are only gently grooved ventrally in Libinia ( Fig. 3 D); (ix) male telson is rather narrow, distinctly triangular, and tight-fitted into the sterno-abdominal cavity ( Fig. 1B ), it is loosely fitted into the sterno-abdominal cavity, broadly triangular or with a rounded tip in Libinia ( Fig. 1D ); (x) G1 is stout, conspicuously straight, only slightly convergent anteriorly ( Fig. 1A ), the G1 is remarkably more slender, deeply curved outward, and tapering gently distally in Libinia ( Fig. 1C ); (xi) G1 keel is well developed, blunt ( Fig. 1A–C ), it is absent in Libinia ( Fig. 1D ).

Libinia Leach, 1815 , is herein restricted to the following eight species: L. cavirostris Chace, 1942 (WA); L. dubia H. Milne Edwards, 1834 (WA); L. emarginata Leach, 1815 (its type species) (WA); L. erinacea (A. Milne- Edwards, 1879) (WA); L. ferreirae Brito Capello, 1871 (WA); L. mexicana Rathbun, 1892 (EP); L. peruana Garth & Méndez, 1983 (EP); L. rhomboidea Streets, 1870 (WA); L. setosa Lockington, 1877 (EP); and L. spinosa H. Milne Edwards, 1834 (WA).

Etymology. The name Stratiolibinia is an arbitrary combination of stratio (Greek for soldier) and the spider crab genus name Libinia . Gender feminine.

Figures

FIGURE 1. A – D, Ventral view of thoracic sternum (abdomen in place in B and D, removed in A and C). A, B, Stratiolibinia bellicosa (Oliveira, 1944) gen. nov., comb. nov., male cl 62 mm, cw 52 mm (MZUSP 22536). C, D, Libinia spinosa H. Milne Edwards, 1834, male cl 62 mm, cw 53 mm (MZUSP 20271). Note in D, lateral swellings (arrows) at level of thoracic sternites VI – VII and abdominal somites 5 and 4 deeply concave laterally. Scale bars: A – D, 15 mm.

FIGURE 3. A, B, right P 2 carpus, propodus, and dactylus. C, D, corneous distal end of left P 2 in ventral view. A, C, Stratiolibinia bellicosa (Oliveira, 1944) gen. nov., comb. nov., male cl 74 mm, cw 64 mm (MZUSP 20288). B, D, Libinia spinosa H. Milne Edwards, 1834, male cl 62 mm, cw 53 mm (MZUSP 20271). Note P 2 dactylus much shorter than P 2 propodus in A (about as long as propodus in B), distinct, ventral tubercle (arrow) behind corneous tip in C (absent in D), and corneous tip deeply excavated in C (gently grooved in D). Scale bars: A – B, 15 mm; C, 0.5 mm; D, 2 mm.