Animal world is one of the main sources of information on ageing and longevity. Several animal species are used to explore the evolution of ageing and to find the remedies to extend human longevity. However, about a third of animal phyla, and usually less, are mentioned in the relevant reviews. We analysed the entire animal world in context of longevity studies choosing for the analysis one of its most general characteristics - the limits of variation of life spans within the main groups. We performed a systematic review of the sources on all groups of animals of the class level and meta-analysis of the values of life spans within them.