Table 1. Comparison of presence and absence of primary characteristics of siliceous sponges (Hexactinellida plus Demospongiae), Calcarea, and Eiffelia.
Characteristic | Silicispongea | Eiffelia | Calcarea |
---|---|---|---|
Axial organic filament | 1 | 0? | 0 |
Hexactine spicules | 1 | 1 | 0 |
Opal-A in spicules | 1 | 1? | 0 |
Rhomboidal first-order grid | 1* | 1 | 1* |
Multiple size orders | 1* | 1 | 1* |
Axial symmetry | 1* | 1 | 1* |
ACC/Mg-calcite in spicules | 0 | 1? | 1 |
Organic spicule sheath | 0 | 1? | 1 |
Hexaradiate spicules | 0 | 1 | 1* |
1, presence; 0, absence; 1*, present in ancestral forms but subsequently lost in at least some extant taxa; ?, character state probably as given, based on our observations, but could not be categorically confirmed with the available material.