Figure 2.

A timescale of arthropod evolution Numbers associated with nodes are divergence times (Ma) and their standard errors (Table 2). Three calibration points were used: the fossil-based divergence of Chilopoda and Diplopoda (423 Ma), the fossil-based divergence of Xiphosura and Arachnida (480 Ma), and the 993 Ma deuterostome-arthropod divergence estimated from a previous molecular clock analysis.