First Vertebrate, possibly 525 mya, at least by 518 mya

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The earliest vertebrate creatures are primitive fish appearing early in the Cambrian Period, but bony fishes with actual bony vertebrae didn’t appear for another 100 million years, until the late Silurian. Fossil evidence for chordata animals that existed before vertebrate animals branched apart into their own subphylum may go back to 550 million years ago, but the first fishes (vertebrate animals) appear about 525-518 million years ago.

Guiyu oneiros is one of the earliest bony fishes, dating back to 419 million years ago. Back at the end of the Silurian and start of the Devonian Period, between about 420 million and 400 million years ago there were many fish with armor plates or shells (dermal bones), and indeed there had been for tens of millions of years already, but internal cartilage or bones were a new innovation. Despite the fact that actual vertebrae only appear around this time, in the late Silurian Period, the subphylum of vertebrata seem to first appear fairly early in the Cambrian period, with species such as Myllokunmingia (from about 525-520 million years ago), the Haikouichthys, Zhongjianichthys rostratus, and Metaspriggina walcotti all appearing in the fossil record from 525-518 million years ago.

Today, there are three subphyla in the Chordata phylum, and the vertebrata are appear in the fossil record near in time as the Urochordata (sea squirts) and Cephalochordata (lancelets). The early fossil record of Cephalochordata seems to start with the Pikaia and Yunnanozoon, both from the early Cambrian, perhaps as old as 524 million years ago, while the earliest Urochordata fossils seem to be Shankouclava shankouense and possibly (doubtfully) the Ediacaran Ausia fenestrata and the Yarnemia from 555-548 million years ago.

In ancient times there were some very strange vertebrates. The Tully monster (state fossil of Illinois, Tullimonstrum gregarium), which lived about 309-307 million years ago, seems to have been a vertebrate, probably related to the lampreys.

  Links about the first vertebrates:

1. The Tunicates are the chordates who were evolutionary ancestors of vertebrates.

2. Berkeley page about Vertebrates in the fossil record

3. History of Vertebrates

4. Did early vertebrates live in salt water or fresh water?

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