Fig. 1

Symbion pandora, dwarf male. Anterior faces to the left in all aspects. aVentral view. The tip of the penis (arrow) is extruded while the base is hidden inside the lumen (double arrowhead) of the penial pouch (pp). The lateral sensoria (ls) are composed of long cilia. b Close-up of the penial pouch of the specimen shown in a. Note the ridges (arrowheads) of the cuticle in the region at the base of the penis (cb). cDorsal view. dLateral view. The frontal ciliated field (fc) extends dorsally, covering the anterior-most third of the male body, and a ventral ciliated field (vc) spans from the most anterior body region until the penial pouch