An unprecedented new genus and family of Tetractinellida (Porifera,Demospongiae) from New Zealand's Colville Ridge,with a new type of mitochondrial group I intron

A remarkable sponge with unprecedented megascleres and systematic affinities was collected recently from a previously unidentified volcano on Colville Ridge to the north‐east of New Zealand. The sponge has the appearance of a tetillid sponge (family Tetillidae Sollas, 1886) with a perfectly spherical external form, radiating internal skeleton of huge oxeas and triaenes, and microspined sigmaspires as microscleres. The triaene megascleres, however, are unprecedented in their form and ornamentation; they are huge clubbed orthotriaenes the upper third of which is acanthose. S tupenda singularis gen. et sp. nov. is described here and the phylogenetic affinity and taxonomic position of this unique sponge is explored in relation to a broad range of tetractinellid sponges (order Tetractinellida Marshall, 1876) using the Folmer + Erpenbeck fragment of the cytochrome c oxidase subunit I (COI) gene and a nearly complete sequence of the 18S rDNA gene. Mitochondrial introns are rare in sponges but S . singularis gen. et sp. nov. possesses a mitochondrial group I intron at position 387 in COI; it hosts a putative LAGLIDADG endonuclease gene. This intron is the first of its kind in sponges: the self‐splicing intron is homologous to a placozoan COI intron whereas the LAGLIDADG endonuclease gene may be related to Fungi LAGLIDADG endonuclease genes. © 2015 The Linnean Society of London