A common cross-species atlas of cortical gray matter.

Comparative neuroscience requires a framework that enables consistent anatomical comparison across species with widely differing brain size, folding, and specialization. We introduce a cross-species hierarchical atlas spanning rodents, nonhuman primates, and humans, built upon population-averaged minimal deformation templates (MDTs) to ensure anatomically consistent alignment. The atlas defines homologous cortical and subcortical regions through landmark-guided boundaries and multimodal nonlinear registration. By aligning each species to its MDT and harmonizing anatomical definitions across species, the framework supports robust comparisons of brain organization at multiple levels of granularity. Validation against species-specific atlases confirmed strong regional correspondence and systematic scaling across species. Released as a freely available resource, this common atlas provides a unified coordinate system to support comparative imaging, developmental studies, and cross-species connectomics.