Whale evolution resolved, but only slightly.

By JW Dowey - 14 Jan 2015 10:36:4 GMT
Whale evolution resolved, but only slightly.

We have no pygmy right whale for you, but this marvellous breach by a Southern right whale, Eubalaena australis, is cause for a celebration that we now have more whales to view in the “right” way, and not as prey for oil lamp fuel. Southern right whale image; Credit: © Shutterstock

When they named the pygmy right whale, nobody realised how the species had evolved. The largest vertebrates are the baleen whales, which evolved with no obvious missing link from smaller, toothed types. In the case of the baleen whales, we seem to have evidence for an ancestor-descendant relationship (ADR.) The pygmy right comes in at 5m (16 feet) with similarities to both the right whale and the grey whale. It has a projected ancestry to the early Miocene, 23 million years ago. Cheng-Hsiu Tsai and R. Ewan Fordyce attempt to resolve some whale ancestry in the Biology Letters of the Royal Society’s Ancestor descendant relationships in evolution: origin of the extant pygmy right whale, Caperea marginata. They have an ideal whale watching position in New Zealand’s University of Otago. Let us hope they spot some new fossils too.

The fossil whale Miocapera pulchra, first described in 2012, fits well in a relationship with both the juvenile skeleton of a pygmy right whale and the adult. It is important to regard the developing animal as a hint of might have happened during ancestral evolution. We are lucky in this case to have what could be a direct ancestor, or in a wonderful but unlikely way, the fossil could have evolved from the living species and then become extinct!

In fact, it seems the living whale has developed neoteny (child-like features) as it adapted to a smaller size and different habits by reducing growth rates during development. The fossil Miocapera is a likely stage during this process, although it is very similar to Capera The old problem of few fossils to compare is relieved by the 2012 discovery, but no other hints are available for those wishing they could link the whales together more efficiently.

The current thinking on baleen whales is clouded by the lack of other fossils since the late Eocene. Toothed predators of fish, squid and dolphins seem to have developed baleen but, don’t know when. Echolocation must have been absent among these whales but other changes are unknown. The eubalaenid and bowhead whales form one successful group of 4 species that is associated with Caperea and its fossil relative. Rorquals and other baleen whales like the humpback and the grey have 9 species. Progress on the evolution of other baleen and the special diet that has produced that largest animal ever (the blue whale) must remain on hold, but at least the process of discovery goes ahead, even if it is slow. We are pleased to see Dr. Fordyce again after his previous paper we noted in Pygmy whale finally found unique!