Fig 6. Morphospace defined by the first three axes of a PCO analysis of the frontalmost appendage.

Analysis based on a matrix of 36 taxa and 12 characters (see Methods and S1 Dataset). Percentage of total variance explained by each axis displayed next to axis names. The pie diagrams describe the relative influence of the characters on each axis (see distribution pie, bottom left to the character list). The outer ring displays the proportional value of the Cramér index represented by all characters having a significant impact on the axis (p-value ≤ 0.05). The inner pie displays the proportional p-value for those significant characters, quantifying their impact on the ordination of the axes. The identity of characters used is shown on a hypothetical synthetic appendage in the bottom right corner. Abbr. Anomalocaris: Anomalocaris canadensis; As: Amplectobelua stephenensis; Ap: Aysheaia pedunculata; Bb: Branchia brevis; Bp: Branchiocaris pretiosa; Cf: Cupiennius foliatus; Ci: Cassubia infercambriensis; Cs: Caryosyntrips serratus; Fp: Fuxianhuia protensa; He: Haikoucaris ercaensis; Hurdia: Hurdia victoria; Ia: Isoxys acutangulus; Jd: Jianshanpodia decora; Kk: Kerygmachela kierkegaardi; Kunmingella: Kunmingella maotianshanensis; Ks: Kiisortoqia soperi; Leanchoiliids = Actaeus armatus, Alalcomenaeus cambricus, Leanchoilia superlata; Li: Lithobius forficatus, Lm: Lightiella monniotae; Mh: Megadictyon haikouensis; Nebalia: Nebalia bipes (Nb1 refers to coding of three rami, Nb2 to a single one); Oo: Occacaris oviformis; Or: Opabinia regalis; Pl: Pycnogonum litorale (extant); Pn: Peytoia nathorsti; Phalangium: Phalangium opilio (extant); Sb: Schinderhannes bartelsi; Surusicaris: Surusicaris elegans; ?Su: Sanctacaris uncata; Tb: Tamisiocaris borealis; Wf: Waptia fieldensis; Yohoiids = Fortiforceps foliosa, Yohoia tenuis.