Geographic range maps for Mammal Diversity Database v1.3 taxonomy

Update of mammal maps based on the taxonomy of the Mammal diversity database. These maps are different from the original, have been downscaled and are distributed under the R package mdd (github.com/alrobles/mdd).本数据集为依据哺乳动物多样性数据库（Mammal Diversity Database）分类学体系更新的哺乳动物分布图谱。该批图谱与原始版本存在差异，已完成空间降尺度处理，并以R软件包mdd的形式对外分发，其源码托管地址为github.com/alrobles/mdd。