Shell stellate, surface radiately ribbed; vertex sub-central; margin of aperture with radiating processes.

Scutellastra is a widespread and paraphyletic group, which consists of three clades with distinct geographical distributions, in the Indo-Pacific, southern Africa and southern Australia. Nakano & Ozawa (2004) suggested that the basal Indo-Pacific branch extended its distribution westwards from the Atlantic to the Pacific in the Cretaceous by rafting on ammonites (Kase, Shigeta & Futakami, 1994). Scutellastra fossils from the Upper Cretaceous of northern Japan (Kase & Shigeta, 1996; Ridgway et al., 1998) suggest that Scutellastra reached Japan from the Atlantic during the Cretaceous. Our estimates show that the Australian and southern African clades of Scutellastra had also diverged by the Late Cretaceous. Cymbula and Helcion are African clades; the single exception is C. depsta, which may have reached the southern Indian Ocean by rafting on algae (Ridgway et al.y 1998).