How can paleontologists determine which animal evolved into which?

Question

There’s plenty of fossils and I get they can be dated pretty accurately but how do we know certain animals are actually related? Most ancestors shown in media about evolution of particular animals look completely different than what they turned into. So how do scientist look at different fossils and determine how they were related?

Also a follow up question: how do paleontologists know they found a new species? Plenty of animals are only known from, like, two teeth or something. How can you definitively call this a separate animal and not just a bit strange or slightly disabled version of a known one?

In: 2

Answer 1

This is one of those cases where people have a very skewed view of what happens in a science field.

It is almost never immediately obvious what the relationship between fossils is.

Multiple times “new species” turned out to be juveniles, or sexual dimorphism, or some other type of variation (like different “castes” of insects). But it’s often after decades of debates and vitriolic rivalries, thanks to new groundbreaking analysis techniques.

Just as often “related” species turn out to be convergent evolution.

And this is just as often the case with living species, much less extinct ones. So aside from the occasional “obvious” relationship, it takes years upon years of nitpicking through finer and finer anatomical details, again often with brand new techniques, to eventually arrive at a relationship that the community can agree on. And even then, it often takes more discoveries to chain together an evolutionary line that wasn’t obvious.

TL;DR It’s really messy and can take decades, with new discoveries inbetween, to come to any sort of consensus.

>Plenty of animals are only known from, like, two teeth or something. How can you definitively call this a separate animal and not just a bit strange or slightly disabled version of a known one?

It’s one of those dirty secrets, but making discoveries is how you get more funding, so of something isn’t previously described or just obviously malformed (like a tumor or fracture), bam new species. Leave it to others to disprove, you have your published paper with a brand new discovery.