Scientists believe that many animals existed
before dinosaurs. Of course, that has a lot to
do with what animals we choose to call dinosaurs!
We call certain animals that lived between the
Triassic Period and the end of the
Cretaceous Period dinosaurs.
The Triassic Period started about 250 million
years ago. But we have studied fossils of animals
that we think were alive 665 million years ago,
during the Precambrian Eon. We have a good
sense of how old these animals are thanks to
carbon dating, an amazing scientific
technique invented by Willard Libby in 1947. But
it's much harder to tell exactly which animal came
first, because we don't have fossil evidence, so
scientists do not know for sure. Since we don't
know, we haven't chosen a name for the first
animal's species, but we did choose a name for the
first animal: we named it the
Dinosaurs were not the first animals alive
on Earth. We don't really know what the first
animal was, because we don't have a fossil record
of it: it would have been microscopic and
soft-bodied, and thus unlikely to leave any fossil
evidence. It probably lived between 650 and 600
million years ago.
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