Fig. 18

Mapping of CNS and midgut characters on pycnogonid phylogeny. The depicted cladogram has been simplified from [12]. Three characters of the CNS (A–C) and one character pertaining to the midgut diverticula (D) are mapped, colored branches represent the different character states schematically depicted in the bottom left corner of each cladogram. In families shown as one collapsed lineage, intra-familial variation of a character is indicated by side-by-side depiction of its different states. Owing to the lack of a well-supported phylogeny and insufficient neuroanatomical sampling at the genus level, transformations along the branches of the morphologically diverse families Ammotheidae and “Callipallenidae” are considered ambiguous (gray) in case of multiple intra-familial character states (A, C). The stippled green line in C relates to the potential inclusion of the genus Paranymphon in the Ascorhynchidae, as indicated in [12]. A Antero-posterior location of leg ganglia: LG3&4 in TS3 (black); LG3 at TS2-3 border (magenta); LG3(&LG4) in TS2 (green). B SEG and LG1: close but anatomically separate (black); set off with distinct connectives (magenta); fused into extended SEG (green). C ISNs and trunk segmentation: complete ISN set in fully segmented trunk (black); reduced ISN set in partially fused trunk (pink); lack of ISNs in completely fused trunk (green). D Structure of leg diverticula: linear (black); multi-branching (green); linear with irregular pouches (magenta)