Bat, Dolphin, Feline, Guinea Pig, Human, Mink, and Cynomolgus Monkey CXCL12 (C-X-C motif chemokine ligand 12), also known as SDF-1 (stromal cell–derived factor-1), is a homeostatic chemokine belonging to the CXC chemokine family that plays a central role in cell migration, immune cell trafficking, and tissue development. In these species, the CXCL12 protein is identical at the amino acid level (100% sequence identity), highlighting the extreme evolutionary conservation of this chemokine and reflecting its essential biological functions across mammals. CXCL12 primarily signals through the receptors CXCR4 and ACKR3 (CXCR7), regulating the migration and positioning of hematopoietic stem cells, lymphocytes, monocytes, and other progenitor cells within tissues. It is produced by stromal cells, endothelial cells, epithelial cells, fibroblasts, and bone marrow niche cells, where it contributes to hematopoiesis, immune surveillance, tissue repair, and organ development. The CXCL12–CXCR4 signaling axis is critically involved in embryonic development, cardiovascular formation, and maintenance of stem cell niches in bone marrow and lymphoid tissues. In humans and closely related primates such as cynomolgus monkeys, CXCR4 also functions as a coreceptor for HIV entry, making CXCL12 an important regulator of viral susceptibility and immune cell trafficking. Because this chemokine is structurally identical across bats, dolphins, cats, guinea pigs, humans, mink, and cynomolgus monkeys, these species provide valuable comparative and translational animal models for studying stem cell biology, cancer metastasis, immune cell migration, and host–pathogen interactions mediated by the CXCL12–CXCR4 pathway.