Post #2698913

Jackdaw and saltwater crocodile, by far! Both belong to the group Archosauria (which also once contained all the jackdaw's dinosaur ancestors), and have a common ancestor about 250 million years ago. They're actually more closely related to each other than either of them is to any lizard - yes, a crocodile is more closely related to a bird than to a lizard. A gecko is precisely as closely related to a salamander as you are, dear reader, at least assuming you're human. Modern mammals and reptiles are both amniotes, a lineage that diverged from that of the modern amphibians way back in the Carboniferous, some 320 million years ago. Amniotes pioneered all the cool features that allowed vertebrates to start living far inland: They got rid of the gill-breathing young stage, developed thicker keratinized (and no longer water-permeable) skin, and developed shelled eggs that could be laid on dry land rather than the gel-based eggs amphibians lay in water. The last common ancestor of a gecko and a salamander is *the same animal* as the last common ancestor of a human being and a salamander. That said: Modern amphibians have evolved just as much since then as we amniotes have, and they have a lot of weird innovations that amniotes never came up with. Frogs are perhaps the most specialized jumping vertebrate of all. There are salamanders that have no lungs and breathe entirely through their skin! And some have independently ditched the tadpole stage and hatch as little "froglets" ... a few species have even adapted to bearing live young rather than laying eggs at all. (One niche modern amphibians have largely left to us amniotes is ... vegetarianism. There is only one known species of herbivorous amphibian in the world.)