The mountain stream siredon belongs to the family Ambystomatidae, or “the mole salamanders”, which diverged from all other salamanders in the Early Cretaceous period over 140 million years ago. This is around five million years before the koala and dolphin lineages diverged from their common ancestor. It occurs in isolated populations on high mountains to the south and west of the Valley of Mexico in the central state of México, southern Distrito Federal, and northwestern Morelos, Mexico. Now categorised as Critically Endangered, the forest and streams which it inhabits urgently need conserving to secure its survival before it falls victim to extinction.