New species of Semnoderidae (Kinorhyncha: Cyclorhagida: Kentrorhagata) from the Gulf of Mexico

Two new species of Semnoderidae from the Gulf of Mexico are described, and the presence of Antygomonas cf. gwenae and a yet undescribed species of Antygomonas is reported. Sphenoderes aspidochelone nov. sp. is recognized by the presence of a first segment forming a closed ring with deep middorsal and midventral incisions, stout, middorsal acicular spines on segments 1 to 11, lateroventral acicular spines on segments 3 to 9, sexually dimorphic laterodorsal spines on segment 10 and minute cuspidate spines in lateroventral positions on segment 5. Semnoderes lusca nov. sp. is characterized by its first segment forming a closed ring with deep, wedge-shaped middorsal and midventral incisions, acicular middorsal spines on segments 1 to 9 and 11, acicular lateroventral spines on segments 2 to 9, crenulated middorsal and midlateral spines on segment 10 and well-developed cuspidate spines on segments 2 (more lateral than acicular spines), 5 (more ventral than acicular spines), 8 (lateral accessory positions) and 9 (ventrolateral positions). A discussion of the diagnostic characteristics of Antygomonas, Sphenoderes and Semnoderes is included. A comparison of these three genera with the specimens recorded in the present study indicates that Antygomonas should be considered as closely related with Sphenoderes and Semnoderes, but it also suggest that A. gwenae could represent a separate lineage within Semnoderidae, and that the species should be reassigned to a new genus.