What Does Evolution Have in Store?

Greetings. Fish, amphibians, reptiles, mammals, and birds (avian dinosaurs.) Complex forms of animal life. 

About 530 million years ago during the Cambrian explosion, fishlike animals with a notochord and eyes at the front of the body, such as Haikouichthys, begin to appear in the fossil record. By the late Cambrian, other jawless forms such as conodonts appear. During the Silurian, jawed and armoured fish appear on the scene, with giant placoderms such as Dunkleosteus, the cartilaginous Chondrichthyes, and the bony Osteichthyes. By the Devonian, fish diversity had greatly increased, including the placoderms, lobe-finned fishes, and early sharks, earning the Devonian the epithet "the age of fishes."

The first major groups of amphibians developed in the Devonian period, approximately 370 million years ago, from lobe-finned fish which were similar in physical characteristics to the extant coelacanth and lungfish. These ancient lobe-finned fish had evolved multi-jointed leg-like fins with digits that enabled them to crawl along the sea bottom. Some fish had developed primitive lungs that helped them breathe air when the stagnant pools of the Devonian swamps were low in oxygen. They could also use their fins to hoist their bodies completely out of the water and onto dry land if circumstances so required. Eventually, their bony fins would evolve into primitive limbs and they would eventually become the ancestors to all subsequent tetrapods, including all modern-day amphibians, reptiles, mammals, and birds.

The origin of the reptiles lies about 320 million years ago, in the humid swamps of the Late Carboniferous period, when the first reptiles evolved from advanced reptiliomorphs. A series of footprints from the fossil strata of Nova Scotia dated to 315 million years ago display typical reptilian toes and imprints of scales. These tracks are attributed to Hylonomus, the most ancient reptile known to modern paleontologists. It was a small, lizard-like animal, about 30 centimeters long, with numerous sharp teeth strongly indicating an insectivorous diet. 

The first mammals appeared in the Late Triassic Period, about 225 million years ago. They expanded out of their nocturnal insectivore niche from the mid-Jurassic onwards. The vast majority of Mesozoic mammals, if not all, are thought to have remained nocturnal, a necessity when under the absolute rule of the non-avian dinosaurs, among other advanced reptiles of the time. The majority of the mammalian species that existed during the Mesozoic Era were multituberculates, eutriconodonts and spalacotheriids. One of the earliest-known forms is Sinodelphys, found in 125-million-year-old Early Cretaceous shale in China's northeastern Liaoning Province. The fossil is nearly complete and includes tufts of fur and imprints of soft tissues.

The birds first appeared during the Jurassic Period, with an exact geologic date yet to be firmly determined. Since all extant birds are avian dinosaurs, and by definition theropods, birds are basically highly advanced, endothermic reptiles. 

So, what comes next? What new complex form does the evolutionary process have in store? What physical characteristics and capabilities will the next form of complex life possess, and when will they appear on the scene? Nobody knows, but it promises to be quite a momentous event. 

Thank you for your time and consideration.