https://doi.org/10.11646/zootaxa.5178.1.4 http://zoobank.org/urn:lsid:zoobank.org:pub:A9C0E7D2-2FFA-4CCE-A1EE-54D72F9C7F82 72 Accepted by J. Hooper: 28 Jul. 2022; published: 24 Aug. 2022 Article ZOOTAXA ISSN 1175-5326 (print edition) ISSN 1175-5334 (online edition) Zootaxa 5178 (1): 072–080 https://www.mapress.com/zt/ Copyright © 2022 Magnolia Press Tale of two species of Stylissa (Porifera: Demospongiae: Scopalinida) from the west and east coasts of India ANITA M GEORGE CSIR-National Institute of Oceanography, Dona Paula, Goa 403 004 India Institute for Environmental Studies and Social Education, 14/C3, Nesamony Nagar, Nagercoil-629 001, Tamil Nadu, India � anitageorge2003@gmail.com; https://orcid.org/0000-0002-4744-4069 Abstract Recent collections from the western and southern coasts of India recorded two species of Stylissa Hallmann (Scopalinida, Scopalinidae). Stylissa soestii sp. nov. was collected from St. George Island in Goa, Hare Island in the Gulf of Mannar and the Palk Bay. It has six distinct different morphologies and sizes of styles, in addition to the typical gently curved stout and thin styles characteristic of Stylissa, and two different morphologies of strongyloxeas and rare strongyles. Stylissa carteri (Dendy, 1889) was reported previously from India (Gulf of Mannar and Pearl Banks of Tuticorin) and is redescribed here from populations in Palk Bay, east coast of India, in addition to Muttom, Vizhinjam and Lakshadweep islands, which are the first records of S. carteri from the west coast of India. Key words: Porifera, sponges, Stylissa carteri, Stylissa soestii sp.nov., west and east peninsular India, St. George Island, Goa, Muttom, Hare Island, Manauli Island, Gulf of Mannar, Palk Bay, Kadmat, Kadmat, Minicoy, Lakshadweep Islands Introduction The genus Stylissa Hallmann, 1914 was previously included in Order Halichondrida, family Dictyonellidae (e.g. Hooper & Van Soest 2002). At that time sponges assigned to the order Halichondrida were characterised in having a fleshy ectosomal layer but without any ectosomal skeleton, and the choanosomal skeleton was dominated by styles and rarely oxeas or strongyles. Specific to the characterisation of Stylissa in the then-erected family Dictyonellidae, the styles are arranged in a vague or confused intercrossing reticulation (Van Soest et al. 2002). The spicule modifications are common among the twelve known species of Stylissa, and are not reliable for species confirmation (see detailed review in Alvarez & Hooper 2011). More recent molecular phylogenetic studies generated many polyphyletic groups and the subsequent establishment of new clades that led to a revised classification of the Class Demospongiae (Morrow et al. 2012, Morrow & Cárdenas 2015). Stylissa is probably non-monophyletic where S. carteri (Dendy, 1889) is likely to be sympatric with S. massa (Carter, 1887), but the two differ in their morphology and depth distributions (Erpenbeck et al. 2017). Similarly, S. flabelliformis (Hentschel, 1912) is distant to S. carteri and S. massa where the latter are likely to go with Order Bubarida pending additional molecular analyses (Erpenbeck pers. comm.). Stylissa is undergoing a significant revision based on diverse molecular investigations, including those of the type specimens which is expected to bring further clarity to the intricacies of this genus. In the meantime, the two species reported in this present article are retained in the genus Stylissa. Currently the genus Stylissa is included in a small (31 species) Order Scopalinida Morrow & Cárdenas, 2015 with only one Family Scopalinidae Morrow, Picton, Erpenbeck, Boury-Esnault, Maggs & Allcock, 2012 which now falls under the subclass Heteroscleromorpha Cárdenas, Pérez & Boury-Esnault, 2012. Scopalinidae contains three genera: Stylissa Hallmann, 1914, Scopalina Schmidt, 1862 and Svenzea Alvarez, van Soest & Rützler, 2002 (de Voogd et al. 2022). Stylissa is differentiated from the other two genera by its erect, flabellate growth forms, conulose and smooth surface, with the choanosome made of spongin fibres supported by megascleres mostly consisting of styles. Of the twelve valid species so far known (de Voogd et al. 2022) only S. carteri has been previously reported