The Porifera class Hexactinellida is a classical deep-sea sponge taxon, with few exceptions (e. g. Rossellidae of the Antarctic shelf) occurring... » More

The Porifera class Hexactinellida is a classical deep-sea sponge taxon, with few exceptions (e. g. Rossellidae of the Antarctic shelf) occurring below 1000 m. In a joint project with WG of Gert Wörheide (Munich Univ.) (DFG: JA1063/13,1-3, WO896/5,1-4), we investigate the phylogenetic relationships of this (maybe oldest) animal old taxon; promising for understanding of Early Metazoan evolution. Since the Cenozoic hexactinellid sponges are almost exclusively restricted to deep water environments, therefore this Porifera class is largely under-investigated. So far, only a very preliminary model based on morphological characters exists (Mehl 1992), and a comprehensive molecular phylogenetic analysis of the Hexactinellida was published (Dohrmann et al. 2008, 2009). Within this project, we investigate the phylogenetic relations between hexactinellid families and genera, beginning with the biggest subclass the Hexasterophora. Ca. 150 morphological characters of the Hexasterophora were compiled into a matrix by presence/absence data, and first steps towards the phylogenetic analysis have been done. The resulting phylogenetic trees are compared with those based on molecular data and with the classical systematics. So far, we find the main hexasterophoran taxa (Hexactinosida, Rosellidae and Euplectellidae) well established as monophyletic and in rather good correspondence with classical systematics and molecular results.

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