Episode 29 – Placoderms, The Armored Fish

Listen to Episode 29 at PodBean, iTunes, or your favorite podcast-place!

In this episode we discuss an interesting and important group of ancient armored fish; Placoderms! We discuss some of their wide variety, their evolutionary significance, and focus a bit on their biggest and most famous member: Dunkleosteus.

In the news
New evidence for a possible link between the Chicxulub asteroid and volcanoes
First tracks of a bipedally running lizard

A new species of slider turtle from the Gray Fossil Site is named after our friend Shawn!
Skates show that the tools for walking on land are very old
Bonus: Humans in North America 100,000+ years ago? The debate continues! [Here‘s a description one of the authors shared on our Facebook page]

File:Dunkleosteus terrelli 2.jpg
Image of a variety of placoderms, by Apokryltaros from Wikimedia Commons.

Placoderms swam the world’s oceans and freshwater habitats from the Silurian to the end of the Devonian (430-360 mya). They dominated the seas as some of the largest predators of the day, while many also prowled the depths as bottom-dwelling ambush predators. They exhibited a huge variety of body designs and adapted to almost every aquatic environment of that time. Their impressive success ended at the Devonian/Carboniferous extinction event.

File:Bothriolepis canadensis.jpg
Bothriolepis canadensis, one of the most common placoderms. Image by Citron / CC-BY-SA-3.0 from Wikimedia Commons.
File:Materpiscis02.JPG
Materpiscis attenboroughi model, one of the species that was found to give live birth! Image by Sularko from Wikimedia Commons
File:Lunaspis broili.JPG
Fossil of Lunaspis broili, image by Ghedoghedo from Wikimedia Commons.
File:Austrophyllolepis ritchiei.jpg
Artist reconstruction of Austrophyllolepis ritchiei, a bottom-dwelling placoderm. Image by  Apokryltaros from Wikimedia Commons.

Dunkleosteus was one of the largest species of placoderm and also one of the largest predators of the Devonian, growing to the size of modern Great White Sharks (6 m). It’s become famous for its impressive set of jaws that also sported an equally impressive bite. The bite force of a full grown Dunkleosteus is estimated between 4400 N and 7400 N. This is one of the strongest bites among all fish, both living and extinct. It even rivals the modern record holders, the crocodilians.

File:Dunkleosteus (15677042802).jpg
Dunkleosteus specimen at the Vienna Natural History Museum, Austria, image by Zachi Evenor from Wikimedia Commons.
File:Dunkleosteus intermedius.jpg
Artist reconstruction of Dunkleosteus intermedius. Image by Dmitry Bogdanov form Wikimedia Commons.

Placoderms were also incredibly important to the evolutionary history of jawed vertebrates (gnathostomes). If you’d like to learn more, check out the links below:

Some fishy links…
Earth Touch: The nasty eating habits of prehistory’s meanest fish
The Conversation: The first vertebrate sexual organs evolved as an extra pair of legs
LiveScience: Evolution’s Bite: Ancient Armored Fish Was Toothy, Too
Ecomorphological inferences in early vertebrates: reconstructing Dunkleosteus terrelli (Arthrodira, Placodermi) caudal fin from palaeoecological data(check this one out to see an alternative reconstruction of the tail of Dunkleosteus based on recent research)

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