Fig. 1

Major phylogenetic hypotheses based on morphological characters of copepod orders, redrawn from A) Ho [11], B) Huys and Boxshall [5], C) Ho [12], and D) Ho et al. [13]. Cyan and yellow boxes indicate the superorders, Podoplea and Gymnoplea [67]. After Huys and Boxshall [5], Platycopioida is classified as a newly proposed Infraclass, Progymnoplea. A new order, Thaumatopsylloida (indicated by blue) is proposed by Ho et al. [13]. Poecilostomatoida and Monstrilloida (indicated by grey) are considered as the subgroup of Cyclopoida and Siphonostomatoida, respectively [16, 19, 20]. Grey dotted lines depict the ambiguous phylogenetic relationships from Ho et al. [13]. Four copepod orders (indicated by red) are examined in this study