Well, close enough. One of my favorite evolutionary concepts is that we humans are but highly derived fish (check out Neil Shubin’s Your Inner Fish sometime to see just how deep and awesomely accurate that statement actually is), and now there is a neat little website called Time Tree that searches the literature to determine just when you diverged evolutionarily from your favorite animals, plants, microorganisms, etc. For example, my personal lineage diverged from that of the mighty spiny dogfish approximately 523.1 million years ago, according to a weighted average between mitochondrial and nuclear data (it even provides links to the sources). You can also get this as an app for your smart phone.
Tip o’ the hat to PZ Myers for this cool find.
Interesting fact I learned from TimeLine: Elasmobranchs don’t predate calcified bones, their ancestors lost that ability.
I also thought the cartilaginous skeleton of elsasmos was basal, not derived. I’d love the see the computers they’ve got running metazoan coalescences.
Homo sapiens and Octopus vulgaris diverged (at their “expert estimate”) 910 mya – that’s not unexpected, though, because it’s just the divergence point between protostomes and deuterostomes.
The divergence point between humans and spiny dogfish occurred basically at the split between bony and cartilaginous fishes, but you can also put other species in as well. I had some fun seeing how long ago Squalus acanthias diverged from some other sharks.