There were many species of dinosaurs and many got extinct long before the whole clade disappeared. I am wondering which species has shown the longest fossile record. Since birds descend from dinosaurs, I excluded that case to preclude the easy answer! I fully understand the vagueness of my question, stemming from the uncertainties associated with the definition of species but I would think that at least some ballpark could be estimated?
Dinosaur biostratigraphy makes it not possible to answer your question through all of history. 8Ma is the highest longevity species I found in a biostratigraphy table. Dinosaurs are faster evolving than crocodilians who have 1/3rd as big a genome as a mouse and 1/6th that of a shark. Adaptive genus existed for 5-30 million years, and well known clades exist for 20-500 Ma.
The most complete geological formations often only cover small spans of history. Generally you will find that paleontologists have few species, and more often groups and genus represented by 10-20 species fragments. The Hell Creek Formation covers 2 million years of history, and has revealed 400 species, of turtles, dinosaurs, metatherians, mammals, turtles, and a very rich image of life at that time, and 90 percent of the geological time scale is represented by only a fragments of fossils.
So, you won't find a good answer for species, perhaps the best way to find out the longest lived genus (i.e. like a dragonfly, all species are in the same family) is by doing some google tricks:
For genus i can find this:
Plateosaurus 214–204 Ma
Thyreophorans group 199.6–66 Ma
Gryposaurus genus 84-73 Ma
Plesiosaurus genus 199.6–175.6 Ma
Gorgonopsians 265–252 Ma
Dimetrodon 295–272 Ma
Pterosaur 228–66 Ma
Mussaurus : 215–203 Ma
Lesothosaurus : 199–189 Ma
Spinosaurus : 112-93
Kronosaurus genus 125–99 Ma
scorpion 430–0 Ma.
Dragonfly 325–0 Ma
brittle star 499Ma-present
some shark genus: 100-0
snapping tortoise 100-0
horeshoe crab 455-0
Fossil fields are incomplete, so the HellCreek time period is very well represented with lots of tyranosaurus, and other time periods are incomplete.
Animals with small genotypes Crocodiles and turtles evolve very slowly, and it gives you an idea of evolution speeds prior to the arrival of mammals, who seem can adapt faster than all previous larte animals.
crocodiles have less than 1/3 of the genes of a mouse and a human tortoises have 2/3rds and so do horseshoe crabs dragonfly have 1/6th the genome size of a mouse sharks have twice as big genome