Fig. 12
Patterns of ontogenetic development in Fuxianhuia. a Ontogenetic trajectory of Fuxianhuia protensa, illustrating alternation between phases of posterior segment addition (slopes), and abdominal to thoracic tergite transformation (plateaus). Dashed lines denote unavailable ontogenetic stages. b Relationship between ontogenetic stage and body size, as expressed by thoracic length, in articulated individuals of F. protensa (n = 57) (Figs. 1, 3, 4, 5, 6, 7, 8, 9 and 10) and Fuxianhuia xiaoshibaensis (n = 4) (Additional file 1: Table S1). Note that the Y axis excludes the three reduced tergites that typify Fuxianhuia from total trunk tergite count