If you want to see what the future ecology of the world might look like, look to Western Europe (excluding Greece), the place where human impact has been greatest.
Among reptiles there are 5 species of turtles, 13 species of lizards and 11 species of snakes.
Only one of these, the European viper, is potentially dangerous to humans, and none of the snakes or lizards exceed about 4 feet in length. Of the turtles 4 are small (up to about a foot in length and 15 pounds), while the green turtles, a type of sea going turtle that sometimes wanders to European shores, are up to 5 feet across and 440 pounds.
There are no crocodiles or alligators in Europe, no tuataras, and no amphisbaenians (the other main types of reptiles in the world, the last consisting of certain worm-like reptiles). There are 300 species of turtles, 2 species of tuataras, 23 species of crocodile related species, and 7,600 species of lizards, snakes and amphisbaenids in the world. Thus, about 1 in 300 reptile species are found in Europe.
There are 26 amphibian species (11 salamanders and 15 frogs and toads). There are 5,296 species of frogs and toads, 555 species of salamanders, and 171 species of caecilian (limbless amphibians) in the world. Thus, about 1 in 200 amphibian species are found in Europe.
One species of salamander, the fire salamander, has mildly poisonous secretions.
Among mammals (all of which are placental, there are no montremes or marsupilas in Europe) the number of species is:
Primates (excluding humans): 1 (the Barbary Ape on found only on Gibralter - introduced)
Terestrial Carnivores: 22 (2 bears, 5 canines, 12 from the weasel family, 3 mongoose/genet -- all introduced, 1 racoon - introduced, and 3 from the cat family)
Odd Toed Ungulates: 2 (both equines)
Even Toed Ungulates: 18 (1 wild boar, 8 cattle, 11 deer)
Rodents: 48 (6 squirrels, 2 beavers, 1 porcupine - introduced, 1 coypu - introduced, 3 dormice, 1 hamster - introduced, 3 lemmings, 21 voles, 3 rats - introduced, 1 gerbil - introduced, 6 mice)
Insectivores: 22 (3 hedgehogs, 4 moles, 15 shrews)
Seals and Walruses: 8 (7 seals, 1 walrus)
Cetaceans (e.g. whales, dolphins): 29
The only mammals capable of hurting humans in a fight in Europe are the wolf, found only in Spain and Italy, the polar bear, found only in Iceland and Scandinavia, the brown bear and the lynx.
Among the major types of mammals not found in the wild in Western Europe are armadillos, sloths, true anteaters, manatees, elphants, hydraxes, aardvarks, elphant shrews, golden moles, scaly anteaters, flying lemurs, tree shews, pikas, civets, hyenas, red pandas, linsangs, skunks, tapirs, rhinoceroses, hippos, peccaries, camels and llamas, and megabats (aka Old World fruit bats).
Thus there are 195 species of mammals in Europe out of a total for the world of more than 4,000. Thus, about 1 in 20 mammal species are found in Europe. About 27 of those species were introduced and are not native to Europe.
There are 700 species of birds in Europe. It has no flightless birdds.
In some areas the numbers are even smaller, such a Britain.
In Britain there are only 68 mammal species, 15 of which were introduced. The mammals consist of 7 species of insectivores (1 hedgehog, 1 mole and 5 shrews), 20 species of bat, 9 species of terestrial carnivores, 5 species of seal, 1 species of Walrus, 3 rabbit/hare species, 6 species of deer, 1 species of wild pig, 2 species of squirrel, 2 species of dormouse, 4 species of mouse, 2 species of rat, 6 species of vole, and 1 species of beaver. The red-necked wallaby was introduced to Britain but is probably extinct in Britain now in the wild. Britain has no primates other than humans or no predators large enough to threaten humans.
Britain has 3 species of snakes, 3 species of lizards, 5 kinds of turtles that have been seen on its shores, 3 kinds of newts (a type of salamander), 2 kinds of toads, and 2 kinds of frogs. There have been 572 species of birds seen in Britain.
Southern Europe has a bit more biodiversity, in part because it is warmer.
In the last ice age (the Pleistocene era), Europe lost, at least, 1 species of cave bear, 2 species of cave lion, a type of saber tooth cat, 6 species of elphants, 5 species of hippos, 2 species of rhinoceroses, 1 species of primates (neanderthals), and 1 species of giant rat.
Since then the animals that have gone extinct in Western Europe include 2 species of lizards, 3 bird species, 2 species of wild cats, 1 whale species, 2 species of pikas, 2 equine species, 3 species of giant shrew, 2 species of dormouse, the forerunner of modern cows, the cave goat, 1 species of true mice, 2 species of ibex, and 1 species of wild dog.