A species of trilobite was found in the fossil record. At its first appearance, it is similar to an ancestor species but differs from the ancestor in several key characteristics. It seems to change little over several million years, then is extinct. This illustrates the concept ofA species of trilobite was found in the fossil record. At its first appearance, it is similar to an ancestor species but differs from the ancestor in several key characteristics. It seems to change little over several million years, then is extinct. This illustrates the concept of punctuated equilibrium. gradualism. developmental evolution. anagenesis. evo-devo.