The rules for naming species go along these lines:
The species name comes in the form of Genus name with capital letter followed by species name with no capitalisation. Then subspecies name (if there is one). For example:
- The polar bear is Ursus maritimus.
- Its close relative the brown bear is Ursus arctos. Same genus name, different species name.
- Some subspecies of the brown bear are Ursus arctos horribilis (grizzly) and Ursus arctos arctos (European brown bear).
When a race (or subspecies) becomes a species: the definition of 'species' for sexually reproducing creatures is a naturally interbreeding population which can produce viable offspring, which in turn can interbreed to produce viable grandchildren. So horses and donkeys are separate species (both in Equus genus) because they don't interbreed naturally - people are involved in getting them to mate and create mules. Also nearly all mules are infertile, so there are no grandkids.
So your sharktooth people having sex with regular humans is not enough to make them the same species as us. There have to be kids and grandkids produced from that regular human/sharktooth sex. If those kids and grandkids are fertile with both sharktooth people and regular people then the sharktooths would still count as the same species as us: Homo sapiens.
That said, features such as giant shark teeth, 8 eyes and so on sound like massive amounts of genetic change! If we found something like this in the fossil record, palaeontologists would invent an entirely new genus for it, because it is just too radically different to be put in genus Homo with us, the Neanderthals, Homo erectus, and so on.
In fact they'd probably invent a new family or order! After all, it is the only mammal on the planet with 8 eyes!
How far back do you want your common ancestor of humans and sharktooths to have existed? Our own species is quite young - probably only been around for 300,000 thousand years. Genus Homo has been around about 2.8 million years. If they've been around for more than 2.8 million years, they will not be genus Homo, and not that closely related to us. Perhaps they evolved from Australopithecus or some other 'apeman'?