It’s hard to imagine a life without a jaw—we need one to eat and interact with one another through speech. Yet like every other part in our body, it didn’t always exist back in life’s evolutionary history.
Strange as it may seem, these fishes thrived in the waters of this planet over 450 million years ago. They were common animals, with fossils of these peculiar creatures having been unearthed since the 1830s. Even with their limited knowledge of the deep time, the era’s scientists noticed that these fishes clearly looked like no other living animal they knew.
When they were first introduced to the public, back in the mid-nineteenth century, biologist Louis Agassiz also noted that these ancient swimmers sported distinctive heavy-duty armor on their heads.
This feature eventually became the name he gave to these “shelled-skin” fishes: ostracoderms.
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