First up, there’s a great (if busy) illustration of the evolutionary ‘tree’ here. As you can see, it’s not so much a tree as a densely packed root system, with most extinctions removed (because otherwise it just look like a solid mass).
And in recent news, scientists have discovered a new species of walking shark. There’s a fascinating video in that article, showing the shark walking along the sea bottom, using their pectoral and pelvic fins to push them along.
There are also a number of walking fish. The axolotl, or Mexican walking fish, is probably the best known, but the waters around south-east Australia are home to 14 species of handfish, who use their hand-like (and footlike) fins to walk along the bottom. If you look at the 4 photos in this National Geographic article, you can see from some of them that there are two fins placed like legs, which is quite unusual for a fish.
The handfish species are all considered threatened to some degree or another – they only live in shallow coastal waters off south-eastern Australia, and individuals tend to stay close to their homes. So their genetic diversity is probably quite low, putting them in danger, as they’ll be less able to weather any threats such as climate change. Scientists are hoping that the clean-up of the Derwent river may help the species to bounce back, by reducing the threat from pollution.
Although handfish are only found around Australia, fossils have been found in the Mediterranean, and scientists suspect the creatures may have lived in oceans around the world millions of years ago. If they’re currently restricted to a small area of shallow water near Tasmania, they’ll be unlikely to survive the warming waters that climate change will bring, as they’ll be unable to migrate to suitable shallows further south.