Of course, if a representative of the fossil is found alive today, it is called a 'livingfossil'. These taxa, mostly at family, genus, and species levels, appear to leapfrog large intervals of geologic time, including the recovery phases following mass extinctions. They seem to elude our most concerted sampling efforts, failing to be accounted for over considerable intervals of time. First, they show that geologists and paleontologists do not know the three-dimensional distribution of fossils, although they may have reasonable estimates in isolated formations. There have been and will always be surprises.
Fossils seem to be constantly extending their geological time ranges.
We should be sceptical of statements to the effect that a particular fossil is an index fossil that is restricted to, say, the Cambrian 'period', or the Permian 'period', etc. Second, such holdover taxa make it hard to believe that the alleged millions of years between the fossil occurrences are real. In this particular example, paleontologists may eventually find fossils of this sponge between the 'Middle Cambrian' and the 'Upper Triassic'. Third, a fossil can be assigned to a different species because it is found at a supposed different geologic time, obscuring the true range of the taxon within the geological time scale. In the case of Nucha, the difference between the Vancouver Island sponge and the Australian sponge was slight, but the former fossil was given a different species name with a question mark after the genus name.