Figure 1. Facetotecta. A–F in The evolutionary diversity of barnacles, with an updated classification of fossil and living forms

Figure 1. Facetotecta. A–F, selected live images of y-nauplii representing some of the morphological diversity: lecitotrophic ones in A, C, D, F; planktotrophic ones in B, E. Note distinct differences in spination and body shapes. G, H, detailed morphology of y-larvae using scanning electron microscopy: G, ventral view; H, dorsal view, showing cuticular facets on the shield. I–K, the drastic metamorphosis from early y-nauplius (I) to last nauplius instar (J) and y-cyprid (K). These three larvae are conspecific. L, higher magnification view of the big rectangular box in K, showing an scanning electron micrograph of the cyprid antennules, with distal hooks (white circles). M, scanning electron micrograph of small square box in K, showing the lateral side of the y-cypris with a spiny labrum. N–P, metamorphosis from y-cypris to free ypsigon. This is most likely to be a larval or juvenile stage of an endoparasitic adult stage in hosts that have yet to be found. The specimens in A, D, F, I–J were sampled in coastal waters in Keelung, Northern Taiwan. The specimens in B, C, E, G, H were sampled on Green Island, Taiwan. The specimens in N–P originate from Sesoko Island, Japan. Abbreviations: a1, antennule; a2, second antennule; ce, compound eye; lb, labrum; mdb, mandible. Specimens J and K provided by Dr. Mark J. Grygier. Specimen J re-photographed from Grygier et al., (2019).