Mammals in the Summacene are more diverse then one would suspect. However, due to a strange quirk in terms of environments, they have been reduced in numbers and size. Herbivores are commonly descended from Rodents, Opossums, Pigs, Mouse Deer and Wombats, which, unsurprisingly, were the right size for this tropical environment. Most herbivores reach a height of 50 centimeters. In Antarctica, the most common mammals found are descended from Rodents, Marsupials and Monotremes. Carnivores are usually descended from Cats, Possums and Mustelids. Semi aquatic and arboreal forms are descended from Lemurs, Possums and Squirrels, with a few forms being descended from Insectivores. Bats have proven to be rather successful, and are the largest mammals, with wingspans often reaching a meter or more. Almost all the mammals present in Antarctica are descended from Rodents of the Dolichotidae and the Muroidea subfamilies.

The Birds of the Summacene are particularly diverse, and are some of the most diverse clades of the period. The largest members, descending from the Tnamiformes order, are found across the world, but are most common in South America and Antarctica, where large forms are quite common. Sparrow descendants, however, are the most common, with them filling in most niches of those who died out earlier on. Apodiformes (Hummingbirds and kin) are also rather common, with their greatest diversity being found in South America and Antarctica. Whilst the northern hemisphere has, surprisingly, relatively few bird descendants, they are commonly found in the southern hemisphere, with a great hot spot being Antarctica, due to its large flowering plant population, and its environment type, which is rain forest.

One of the most diverse animals in the Summacene are crocodiles, surprisingly. Being descended from the Cuvier's Dwarf Caiman (Paleosuchus Palpebrosus), a new order of stupendously diverse crocodiles has formed, and are found world wide, the Parvosuchia (Meaning "Small" in Latin, although there are a few large (4 meter) forms). These usually tiny crocodiles have radiated in terms of niches, with insectivorous, herbivorous and fully carnivorous forms being found world wide. The smallest forms, weighing 20 grams, with lengths of a petite 3 centimeters, are the most common, with one genus even being found in the Avargatom mountain range, a set of mountains (Avargatom meaning "Giant" in Mongolian, due to their location) found in Asia, like their predecessor. Herbivorous forms of crocodilians are usually 1-3 meters long, although 4 meter giants have often been recorded. These usually resemble the Aetosaurs of the Mesozoic, although some forms resemble the Ankylosaurs. Some members of another order, the Carnosuchia (Flesh Crocodiles in Latin), mostly resemble the Baurusuchids, and have a similar lifestyle. Some more normal forms have been recorded, with semi-aquatic forms being found in the shallow seas that have popped up around the world.

This group has done very well in these wet conditions, like the crocodiles, the Lissamphibia has gone under another radiation. Mostly descended from the Frogs and Salamanders, various new groups have been reported, with some ambush predators here and there. One group of Salamander descendants has gone under a fully aquatic lifestyle, only returning to the land to breed, like the Pinnipeds of the 21st century. Caecillians have gone extinct, due to habitat destruction and lack of food, and where just to specialized to survive further. Many fossorial, aquatic, terrestrial, arboreal and aeria forms are present.

This is one of the more diverse groups, like the Crocodilians. Unlike their Archosaurian counterparts, Squamates usually reach 30 cm- 2 meters in length, with some marine forms reaching 5 meters. Aquatic forms are more like Otters, which have gone extinct. These forms are usually 30-40 cm long. Egg eating forms are also surprisingly common, with these being some of the more larger forms. These almost lack teeth except for two prongs which allow them to nip both plants and steal eggs from the dominating Crocodiles. A few gliding forms are present, having, more or less, a resemblance to the Draco Volans of the 21st century. Herbivorous forms are usually descended from Iguanas, and reach lengths of 3 meters or more, and are found in South America and Antarctica. The only snakes present are descended from the Boids, which where actually some of the more larger predators of the Summacene.

This interesting order, to which the Tuatara belongs to, is actually among the most diverse order of animals in the Summacene. Once New Zealand, along with Australia, collided with Asia, descendants of the Tuatara began to diversify, and even out compete lizards of the continent. A diverse bunch of large (2 meter) long Tuatara descendants are found in the Avargatom mountain range. A few aquatic forms also exist, along with plentiful lizard like and fossorial forms being present.

Fish are the most diverse aquatic animals of the Summacene. Due to the enlarged swamps and rivers, they found new ways to proliferate. Goldfish descendants make up the bulk of these estuarine inhabitants, although a few predators (Usually reaching 3 meters or more) are descended from the Electric Catfish. Sluggish fish descendants also inhabit the murky swamps that are oh so proliferate, with gaping maws often being found in the murky waters. Filter feeding fish (Being descended from the Parrot Fish) are found throughout the open ocean, with smaller, herbivorous forms being found in the swamps and oceans of the world.

Most of the insect orders of the 21st century are present, and have diversified some more. A few descendants of snails are browsers, with lengths of 10 centimeters often being reported, using their long necks to reach up into the underbrush. Ambush predators, descended from Spiders, are also found, and are even present in the Avargatom mountain range, often reaching lengths of 5 centimeters or more. Jellyfish have diversified, producing many bizarre forms, with some predators here and there. A few Sea-Cucumber descendants (Although still small) have produced both Filter-Feeding forms and Ambush Predators. Some Sea hare descendants have produced forms not to dissimilar to the Charnia genus of the Precambrian, along with some Sessile forms. Others still have replaced the now extinct corals, and produce mile wide compact walls, which, once again, form a stable ecosystem.