Sublime

The backbone, which is horizontally oriented and perpendicular to the hind limbs in horses and mice and whales and basically all other mammals, rotated to become parallel to the legs, and took on a curved shape.

their amniotic eggs, with membranes to nourish, protect, and keep their embryos moist. They moved freely across the land, establishing connections between regions that were previously isolated, and in doing so, evolving new species, new body types, larger size, new diets, new behaviors.

Each vertebral body has four flattened surfaces, called facets, on the posterior side, which are covered with cartilage to facilitate fluid movement and to protect the bony surfaces.

Carrier’s constraint, which plagues amphibians and reptiles that wiggle their bodies sideways, left to right, during their sprawling walks. Such lateral flexion means that one lung is always expanded while the other is compressed, making it difficult for these animals to move and breathe at the same time, greatly limiting their speed and agility. C

amniotes, more specialized tetrapods named for their amniotic eggs, whose internal membranes surround the embryo to protect it and prevent it from drying out. These new eggs unlocked a great new potential: the amniotes no longer were handcuffed to the water but could lay their eggs inland, giving them access to new frontiers.