No somethings only have one cell. they are called unicellular organisms.
Dinosaur fossils had been known for centuries as "dragon bones" or the remains of giants, but it wasn't until Dean William Buckland of Oxford, England described the carnivorous "lizard" Megalosaurus<span> (in 1824) that they were formally studied as an extinct group of giant reptiles</span>
<h2>540 million years ago
</h2>
Paleozoic.
Era immediately follows Precambrian It lasted about 4.5 billion years.
When did abundant fossil evidence first appear in the geologic record.
540 million years ago.
<span>The group includes their common ancestor but also the seeded descendants of that same ancestor.</span>
