Fig. 19

Stratigraphically calibrated cladogram, as shown in Fig. 18. 1, 2, Refer to records of Mesotremaster from the Bajocian (M. felli) and Oxfordian (M. zbindeni) which are closely related to the extant T. mirabilis. 3, 4 Refer to unpublished records of a korethrasterid close to Peribolaster from the Cenomanian and Campanian of the UK. 5, 6 Are records of Pteraster spp. from the Upper Cretaceous (Campanian and Maastrichtian) of northwest Europe. It is clear that a large part of the evolution in the group took place either in the Early or Middle Jurassic