Figure 4
Time-calibrated phylogeny of heterobranch gastropods and distributions of different types of head and shell morphologies. Tree reconstruction was based on combined four-gene sequences and calibration priors placed on three nodes and performed in BEAST. Numerals on branches are Bayesian posterior probabilities; asterisks denote full support (PP: 1). Numbered circles at nodes indicate major clades, including (1) Heterobranchia, (2) Tetratentaculata nov., (3) Mesoneura nov., (4) Allomorpha, (5) Tjaernoeioidea nov., (6) Parvaplustridae nov., (7) Euthyneura, (8) Acteonimorpha, (9) Ringipleura, (10) Nudipleura, (11) Tectipleura, (12) Euopisthobranchia, and (13) Panpulmonata. Pictograms of head morphology suggest two pairs of tentacles existed at node 2 (hence new name Tetratentaculata: ‘bearing four tentacles’). Colour-coded circles at terminals show phenotypic plasticity of shells in Tetratentaculata, particularly in Euthyneura. Abbreviations: CG, cerebral/cerebropleural ganglion; FT, foot; S + N, snout with snout nerves; T + 2N, single tentacle with two nerve cords (green area); TA + N, anterior/labial tentacle with one or two nerve pairs (blue area); TP + N, posterior tentacle or rhinophore/ommatophore with single nerve (yellow area). Head schemes of Aplysia, Archidoris and Achatina after13, anterior side is up. See Supplementary Fig. S3 for further comparison.
