We are independent & ad-supported. We may earn a commission for purchases made through our links.
Advertiser Disclosure
Our website is an independent, advertising-supported platform. We provide our content free of charge to our readers, and to keep it that way, we rely on revenue generated through advertisements and affiliate partnerships. This means that when you click on certain links on our site and make a purchase, we may earn a commission. Learn more.
How We Make Money
We sustain our operations through affiliate commissions and advertising. If you click on an affiliate link and make a purchase, we may receive a commission from the merchant at no additional cost to you. We also display advertisements on our website, which help generate revenue to support our work and keep our content free for readers. Our editorial team operates independently of our advertising and affiliate partnerships to ensure that our content remains unbiased and focused on providing you with the best information and recommendations based on thorough research and honest evaluations. To remain transparent, we’ve provided a list of our current affiliate partners here.

What are Placoderms?

Michael Anissimov
By
Updated Jun 04, 2024
Our promise to you
All Things Nature is dedicated to creating trustworthy, high-quality content that always prioritizes transparency, integrity, and inclusivity above all else. Our ensure that our content creation and review process includes rigorous fact-checking, evidence-based, and continual updates to ensure accuracy and reliability.

Our Promise to you

Founded in 2002, our company has been a trusted resource for readers seeking informative and engaging content. Our dedication to quality remains unwavering—and will never change. We follow a strict editorial policy, ensuring that our content is authored by highly qualified professionals and edited by subject matter experts. This guarantees that everything we publish is objective, accurate, and trustworthy.

Over the years, we've refined our approach to cover a wide range of topics, providing readers with reliable and practical advice to enhance their knowledge and skills. That's why millions of readers turn to us each year. Join us in celebrating the joy of learning, guided by standards you can trust.

Editorial Standards

At All Things Nature, we are committed to creating content that you can trust. Our editorial process is designed to ensure that every piece of content we publish is accurate, reliable, and informative.

Our team of experienced writers and editors follows a strict set of guidelines to ensure the highest quality content. We conduct thorough research, fact-check all information, and rely on credible sources to back up our claims. Our content is reviewed by subject-matter experts to ensure accuracy and clarity.

We believe in transparency and maintain editorial independence from our advertisers. Our team does not receive direct compensation from advertisers, allowing us to create unbiased content that prioritizes your interests.

Placoderms are an extinct class of armored fishes, the first known animals of any type to evolve true jaws. Placoderms evolved from agnathan (jawless) fishes in the Silurian period, about 425 million years ago. This is around the same time as the first terrestrial animals, such as millipedes, are known to have ventured on the land.

Placoderms (class Placodermi) diversified in the mid-Silurian or possibly earlier, an early pioneer in vertebrate evolution that would continue with the Devonian period immediately afterwards, which featured so much fish diversification that is has been dubbed "The Age of Fishes." Unfortunately, no complete placoderm fossils are known — the species have been described from fragments of their body armor that are preserved when the fishes' body breaks apart after death.

The characteristic feature of placoderms is a layer of segmented armor across the head and thorax. Depending on species, the remainder of the body would be scaled or naked. Instead of true teeth, placoderms grinded their food using sharpened points of bone which protrude from the head. This method of feeding is a clear evolutionary intermediate between jawless fish and the highly adapted toothed jaws of modern fish groups.

Placoderms ranged in size from a few inches to the huge 6 m (20 ft) Dunkleosteus telleri, which lived about 360 – 415 million years ago and weighed a ton. Dunkleosteus is considered the first vertebrate superpredator, and probably took over some segments of the evolutionary niche previously occupied only by large predatory invertebrates such as sea scorpions. These animals demonstrated the ability of members of phylum Chordata (vertebrates) to occupy the apex predator niche, which they would continue to dominate for the rest of history. Dunkleosteus is thought to have had a bite force similar to that of the strongest biters in history, like Tyrannosaurus rex modern crocodiles.

Placoderms were also the first animals to internalize egg fertilization, leading to the first live births in evolutionary history. They perished in the late Devonian extinction, which also wiped out practically all jawless fishes as well as numerous other species.

All Things Nature is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Michael Anissimov
By Michael Anissimov
Michael Anissimov is a dedicated All Things Nature contributor and brings his expertise in paleontology, physics, biology, astronomy, chemistry, and futurism to his articles. An avid blogger, Michael is deeply passionate about stem cell research, regenerative medicine, and life extension therapies. His professional experience includes work with the Methuselah Foundation, Singularity Institute for Artificial Intelligence, and Lifeboat Foundation, further showcasing his commitment to scientific advancement.
Discussion Comments
By chrisinbama — On Oct 22, 2010

As the article stated, the very first record of the jawed Placodermi was from the Early Devonian, about 400 million years ago. The placoderms flourished for almost 60 million years and were almost completely gone at the end of the Devonian.

There is nothing known of their ancestors, who must have existed in the Silurian. After the placoderms, the evolution of several other better adapted fish groups followed.

Michael Anissimov
Michael Anissimov
Michael Anissimov is a dedicated All Things Nature contributor and brings his expertise in paleontology, physics,...
Learn more
All Things Nature, in your inbox

Our latest articles, guides, and more, delivered daily.

All Things Nature, in your inbox

Our latest articles, guides, and more, delivered daily.