Hi all, sorry for the delayed response! Thanks for tagging me, Eleanor. Definitely from a large cetacean, and if Pliocene or late Miocene, baleen whale is the most likely possibility. Unfortunately as @lcone stated above, it’s not really possible to say much more about the specimens.
HOWEVER – please keep your eyes peeled for skull fragments and earbones! South Africa has a limited but very critical assemblage of marine mammals that is poorly documented, but efforts by my colleauge Romala Govender are changing that. If you find anything further that is more diagnostic (i.e. skull bits and earbones), then I strongly recommend contacting Dr. Govender at Iziko Museums.