Animals feed
450M
The shark lineage predates the earliest known forests, but the often quoted 450-million-year date comes from scales whose exact identity is debated. It does not mean modern shark species have remained unchanged since then.
3
Octopuses have three hearts: two supply the gills and one supplies the rest of the body. Their oxygen-carrying protein contains copper and turns blue when oxygenated.
Cubes
Wombats produce distinctly cube-like droppings, shaped inside the intestine rather than by a square opening. Research links the shape to differences in the mechanical properties of the intestinal wall.