Another cladogram, but no new fossils

Jean-Renaud Boisserie and colleages published in the most current issue of the Proceedings of the National Academy of Sciences of the USA a peculiar little article where they present a new cladogram on the "Cetartiodactyla" hypothesis.
Over the last three years there has been a paradigm shift in the theories regarding the origin of whales; that they are true Artiodactyls and most closely related to Hippopotami rather than evolving from archaic ungulates. However, little is known of fossil Hippopotami before the early Miocene. A geological gap occurs in subsahara Africa from the Cretaceous to early Miocene. This gap has left a mystery for early Artiodactyla evolution. Yet rather than state this preservational gap in the fossil record, the authors bemoan other researchers, while presenting their own ideas with a cladogram, without the addition of new fossils. Their study still leaves the mystery... how the tiny early artiodactyl Diacodexis became the whale Pakicetus in such a short amount of time. And is there a Paleocene diversification of artiodactyls that we don't know about in Africa?