Figure 15 in Systematics and spicule evolution in dictyonal sponges (Hexactinellida: Sceptrulophora) with description of two new species

Figure 15. Evolution of sceptrules, with two alternative scenarios for the origin of aspidoscopules. The trees are based on the phylogeny shown in Figure 2, reduced to genus level, and nodes with <70% bootstrap support collapsed. The two farreid genera not sampled here, Claviscopulia and Asceptrulum, are shown with dotted lines in their predicted position (polytomies indicate uncertainty of exact placement within Farreidae). Sceptrule types of terminal taxa, inferred sceptrule types at internal nodes, and inferred character state transitions along branches are shown. Left scenario: the stem species of Farreidae possessed regular scopules, which evolved into aspidoscopules in the stem species of Aspidoscopulia (i.e. aspidoscopules are an autapomorphy of Aspidoscopulia). Right scenario: alternatively, aspidoscopules might already have evolved from regular scopules in the stem lineage of Farreidae and were subsequently lost or transformed in all farreid genera except Aspidoscopulia (i.e. aspidoscopules are a plesiomorphy of Aspidoscopulia). Crosses indicate spicule loss (all sceptrules in the case of Asceptrulum); asterisks indicate spicule loss within genera (aspidoscopules in Aspidoscopulia ospreya sp. nov. and clavules in Lonchiphora antarctica). See text for further discussion.