Taxonomy of Oncaeidae (Copepoda, Poecilostomatoida) from the Red Sea.: V.: Three species of Spinoncaea gen. nov (ivlevi-group), with notes on zoogeographical distribution

Three small species of Oneaeidae (two of which are new to science) are described from the Red Sea, representing the ivlevi-group as defined in a recent phylogenetic study of oncaeid species by Bottger-Schnack & Huys in 2001. All species are characterized by (1) the modification of caudal rami seta III into a strong spiniform element, (2) the undulate or lobate hyaline frill at the posterior margin of urosomites and(3) the reduced number of six elements on the maxillule. A new genus, Spinoncaea, is proposed to accommodate all oncaeid species sharing these characters. Red Sea specimens of S. ivleui (Shmeleva, 1966) comb. nov. were identified by comparison with copepod material collected in the Adriatic Sea (type locality), because the original descriptions are deficient and type material is no longer extant. Spinoncaea humesi sp. nov. can be readily distinguished by the different spine count on the distal exopod segment in P2, showing two instead of three spines. Spinoncaea tenuis sp. nov., which had been recorded as Oncaea sp. K in the earlier ecological studies, differs from its congeners by a smaller and more slender caudal, seta III and differences in urosome segmentation. Form variants of S. ivleui and S. tenuis sp. nov. from the southern Red Sea, various geographical locations are described and their taxonomic status is discussed. Species of Spinoncaea are closely related to Oncaea prendeli Shmeleva, 1966 and O. tregouboui Shmeleva, 1968, and to Monothula subtilis (Giesbrecht, 1892) and Oncaea curvata Giesbrecht, 1902. The phylogenetic relationships of these species, which form a robust clade within the Oncaeidae, are briefly discussed. Ecological data of Spinoncaea species in the Red Sea are summarized. First data on the zoogeographical distribution of the described Spinoncaea species in the Indo-Pacific region are presented, thereby confirming a circum-global distribution of Spinoncaea species at low latitudes. (C) 2003 The Linnean Society of London, Zoological journal of the Linnean Society, 2003, 137, 187-226.