| 1 | They have no direct toxic effects on vertebrates. | |
| 2 | The end of the Devonian was a crucial time for vertebrates. | |
| 3 | No squirrels are known to hunt vertebrates, or even scavenge meat. | |
| 4 | The backs of vertebrates evolved as a kind of horizontal pole under which guts were slung. | |
| 5 | It is the first time any vertebrate larva has been found to use sound to communicate underwater. |