In vertebrates, the endocranial surface records some degree of information about the size and sometimes shape of the brain that it originally housed. These impressions represent palaeoneurology’s basic data. Starting in the early 1800s, workers in palaeoneurology have attempted to determine how the brain of vertebrates has evolved through time. Early palaeoneurologists relied on the chance finds of damaged skulls or endocranial casts, and made qualitative assessments of the shape and size of the original brain in these fossils. Jerison introduced quantitative approaches to analysis of brain size, and this is still used today. Recent advances in noninvasive imaging have increased the number of taxa for which brain morphology is known, and it may now be possible to apply quantitative analysis even to the relative size of brain regions. If correlations between behaviour, sensory adaptation and relative brain region size are found using such approaches, palaeoneurology may be able to offer a line of evidence to complement inference of behaviour from skeletal adaptations in extinct taxa.