Ancient species living in earth with all its close relatives dead are called living fossils.
Step-by-step explanation:
Living fossils are interesting as well important creations of nature. Let's take an example of a plant Ginkgo biloba. Its a plant of gymnosperm family along with pine and fir, but belongs to the order Ginkgoales. In this order, Gingko biloba is the only plant that's alive till now, all the other species are dead.
Living fossils give us important informations about the adaptation that used to prevail in earth that lead to survival of species in contemporary times. It also establishes relationships between the two or more phyla of organisms in a taxonomic way.
Animal living fossils are lungfish, horse shoe crab, coelacanth fish, Tuatara, lobe finned fishes etc.