Phylogenetic relationships of sponges with placochelae or related spicules(Poecilosclerida, Guitarridae) with a systematic revision

All the currently known sponge species bearing placochelae or placochelae-l ike spicules (i.e. belonging to the genera Guitarra, Coelodischela, Tetrapo cillon, Euchelipluma, and Hoplakithara) have been reviewed and their relati onships delineated by cladistic analysis. A matrix of 18 taxa and 14 charac ters is included. The species Isodictya palmata and Esperiopsis fucorum wer e used as an outgroup, because they shared either monactines or diactines a nd smooth palmate isochelae with different members of the ingroup. Cladisti c analysis using PAUP produced two equally parsimonious trees of 33 steps ( CI=0.758). Strict, Semistrict and Majority Rule consensus trees displayed t he same topology. The phylogeny of the trees was not totally resolved. The bootstrap 50% majority-rule consensus tree supported, to a greater or lesse r extent, the previously detected monophyletic groups. A common linkage for the ingroup was found in 72% of instances. The genus Euchelipluma appeared as monophyletic in 75% of instances while the group which included the gen us Guitarra did so in 66%. The monophyly of the species with sigmoid micros cleres and without spiny isochelae (G. isabellae/sigmatifera/antarctica/den dyi and C. diatomorpha/massa) received 56% support as did the group of spec ies with spiny isochelae, whereas monophyly of the group laplani/bipocillif era received 64% support and the genus Tetrapocillon 56%. According to our cladistic analysis, all the species bearing placochelae or derived forms sh ould be allocated to Guitarridae. Within this family, the genus Eucheliplum a appeared as monophyletic while Guitarra was paraphyletic. The single spec ies of the genus Hoplakithara clearly belongs to the Guitarra (sigmatifera) group and thus becomes synonymous with Guitarra. G. solorzanoi is consider ed here a synonymy of C. laplani. A diagnosis for the 10 valid species of G uitarra known to date as well as for the two species of Coelodischela and t he two of Euchelipluma is given. (C) 2001 The Linnean Society of London.