• Corpus ID: 89039996

Lonchodactylus messingi, a New Genus and Species of Cyclodorippidae (Crustacea: Decapoda: Brachyura) from the Bahamas

@inproceedings{Tavares1996LonchodactylusMA,
  title={Lonchodactylus messingi, a New Genus and Species of Cyclodorippidae (Crustacea: Decapoda: Brachyura) from the Bahamas},
  author={Marcos Domingos Siqueira Tavares and Rafael Lemaitre},
  year={1996}
}

• M. Tavares, R. Lemaitre
• Published 1996
• Biology

—A new genus and species of the family Cyclodorippidae, Lonchodactylus messingi, is described from specimens collected in the Bahamas using a research submersible. The new genus is more closely related to two Indo-West Pacific genera (Genkaia Miyake & Takeda and Phyllotymolinum Tavares) than to any other cyclodorippid from the coasts of America. Morphological similarities and differences between these genera are discussed. Six genera and twenty species of the family Cyclodorippidae Ortmann, 1892, are known from the western Atlantic and eastern Pacific of the Americas (Tavares 1993a). Five of these genera are restricted to the New World waters, while Corycodus A. Milne Edwards, 1880, has one species in the western Atlantic and four in the IndoWest Pacific (Tavares 1993b). With the present discovery in the Bahamas of a new genus and species of this family, knowledge of the western Atlantic cyclodorippid fauna is now broadened. The description presented herein is based on two specimens collected during dives in the Bahamas of the research submersible Johnson Sea Link I (JSL I) in 1993. The specimens were obtained while conducting studies on the ecology and taphonomy of stalked crinoids. The specimens have been deposited in the collections of the National Museum of Natural History, Washington, D.C. (USNM). Descriptive terminology follows that used by Tavares (1991). Measurements of carapace length X carapace width are given in millimeters (mm). Abbreviations: MXPI-3, first to third maxillipeds; P2-P5, second to fifth pereopods. Lonchodactylus, new genus Type-species. —Lonchodactylus messin gi, new species, by present designation and monotypy. Diagnosis.—Carapace longer than wide, slightly narrowing in width posteriorly. Fronto-orbital width more them half carapace width. Lateral margin between branchial tooth and posterior margin well defined. Dorsal surface weakly sculptured, frontal and hepatic regions depressed. Front bluntly subtriangular, with 1 low rounded tooth on each side. Lateral branchial tooth well developed. Lateral protogastric nodosity distinct. Mesial protogastric nodosity inconspicuous. Gastric pits well marked. Gastric and cardiac regions outlined laterally by shallow, smooth furrows. Exorbital tooth prominent, directed anterolaterally. Orbit shallow, dorsal margin well defined, interrupted by shallow notch; ventral margin poorly defined. Lateral infraorbital tooth well developed. Eyestalk mobile, transverse in position relative to carapace axis. Antenna with article 1 mobile; articles 2, 3 fused in form of broad plate; articles 4, 5 broad. Prostomial chamber short, shallow. Palp VOLUME 109. NUMBER 3 465 of MXP3 visible in ventral view, inserted just below inner angle of merus; segments 2, 3 compressed dorsoventrally. Exopod of MXPl-3 with long flagellum. Chelipeds similar in size and shape. P2 and P3 similar, dactyls lanceolate, laterally compressed; carpi each with 2 obtuse lobes on dorsodistal angle. P4 and PS short, subdorsal in position; dactyls hook-like, simple; carpi each with acute lobe on dorsodistal angle. Thoracic stemites 6-8 nearly perpendicular to plane formed by sternite 5; thoracic stemites 6, 7 contiguous. Sternal suture between stemites 7 and 8 very long, openings of spermathecae almost contiguous. Female abdomen with 7 broad segments entirely covering thoracic stemites 5-8 leaving no exposed sternal portions between lateral margins of abdomen and coxae of P2-P5. Females with first pleopod vestigial, uniramous, and inserted on ventral face of abdominal somite; pleopods 2-S biramous; pleopod 5 shorter than pleopods 2-4, not carrying eggs. Gender.—Masculine. Etymology.—The generic name is formed by the combination of two Greek words, lonche, spear, and daktylos, finger, and refer to the spear-like dactyls of P2 and P3. Remarks.—This new genus shares more characters with two Indo-West Pacific genera, Genkaia Miyake & Takeda, 1970, and Phyllotymolinum Tavares, 1993b, than with any other cyclodorippid genera from the western Atlantic or eastern Pacific. The three genera share the following characters which distinguish them from all others in the family: 1) endostome short and shallow, whereas in other genera in the family the endostome is long and deep; 2) exopod of MXP3 with a well developed flagellum, whereas all other genera in the family lack a flagellum; 3) palp of MXP3 inserted near inner angle of merus and visible in ventral view, with segments 2 and 3 compressed dorsoventrally, whereas in all other genera in the family the palp is inserted on the inner face of the mems, hidden in ventral view, with articles 2 and 3 subcylindrical; 4) abdomen in both sexes with seven segments (number of segments in male of L. messingi not known), whereas in all other genera the abdomen in both sexes has less than seven segments, usually five in males (5-7 fused), and six in females (6, 7 fused), except for Corycodus with seven segments in the female; 5) in males, the abdominal somites cover thoracic stemites 5-8 so that no sternal portions are exposed between the lateral margins of the abdomen and coxae of P2-P5; in males of all other genera in the family the abdomen is narrow, leaving exposed the sternal portions between the lateral margins of the abdomen and coxae of P2-P5. Lonchodactylus can be differentiated from both Genkaia and Phyllotymolinum by the spermathecae (sensu Tavares & Secretan 1993) and thoracic stemites. In Lonchodactylus, sternal sutures 7/8 are very long, and the openings of the spemathecae, located at the end of these grooves, are almost contiguous; in Genkaia and Phyllotymolinum, the openings of the spermathecae are well separated. In Lonchodactylus, the openings of the spermathecae are not indicated by a distinct bulge as in Genkaia and Phyllotymolinum. In Lonchodactylus, sternites 6-8 are nearly perpendicular relative to the preceding stemites; in Genkaia and Phyllotymolinum the stemites are at about 50". Lonchodactylus can be readily separated from Genkaia by the shape of the plate resulting from the fusion of antennal articles 2 and 3. In Ltmchodactylus, the plate is not expanded anteriorly (Fig. 2b); in Genkaia the plate is expanded, and distinctly overreaches antennal article 5 (see Tavares 1993b, fig. lib). In Lonchodactylus, the epLstome is twice as long (Fig. 2b) as in Genkaia (see Tavares 1993b, fig. lib). In Lonchodactylus, the dactyls of P2 and P3 are broad, spear-like (Figs. 1, 2d); in Genkaia the dactyls of P2-P4 are slender (see 466 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON Fig. 1. Lonchodactylus messingi. new genus and species. Holotype. dorsal view: ovigerous female, 6.8 X 6.3 mm. Bahamas. 26°38'N. 78°58'I33'W, 262 m. USNM 275920. Tavares 1993b, figs. 10b, lie). In females of Lonchodactylus, thoracic stemite 7 does not overlap stemite 6; in females of Genkaia, stemite 7 partially overlaps stemite 6. Lonchodactylus differs from Phyllotymolinum by the presence in the former, of vestigial, uniramous pleopods on the first abdominal somite in females. First pleopods are absent in females of Phyllotymolinum. Lonchodactylus messingi, new species Figs. 1, 2 Material examined.—South of western end of Grand Bahama Island, Bahamas: holotype, ovigerous female, 6.8 X 6.3 mm, JSL I Dive 3476, 26°38'N, 78''58'133"W, 262 m, 16 May 1993, coll. C. G. Messing, USNM 275920; paratype, immature female, 3.7 X 3.2 mm, JSL I Dive 3635, 26°38.6'N, VOLUME 109, NUMBER 3 467