According to National Geographic, current estimates put the total number of animal species at somewhere between 3-100 million, a range that leaves a lot to the imagination. The numbers in the infographic above are compiled from a variety of sources and are considered educated guesses in the categories listed. I’ve noticed that in many popular science phylogenetic trees and species graphics, we vertebrates seem to end up on top or at the end of all currently known evolution; an obvious choice because we developed later than the other species. But somehow, I suspect that if insects and arachnids were compiling these lists, if sheer numbers, combined weight, length of time on the planet and plain old survivability counted more than evolutionary youth, brain size and number of new features, the emphasis might be quite different.
If the number of vertebrates seems small and mostly catalogued by human hand, we can take comfort in thought that only 20% of all estimated insects have been found, and there are likely still a half a million species of arachnid to be found. Plenty of stuff for scientists, explorers and the makers of scary movies.
Infographic: 5W Infographics; A. Stegmaier, NGM staff Sources: IUCN; A.D. Chapman, Australian Biodiversity Information Service