Animal Armageddon
Acanthodian
Spawning All Modern Fish: Acanthodians were among the earliest known vertebrates with jaws. Their new adaptation allowed them to nibble flesh off prey instead of waiting for morsels of food to float by. They swarmed anywhere there is a carcass. Once a rare and lowly life form, fish like acanthodian were beginning to take over our planet in the wake of the Ordovician-Silurian extinction event. Every fish we know today — catfish, swordfish, minnows, sharks — would all be spawned from these ancient ancestors.
Bony and Spiny: The acanthodians' scales were not thin and slimy like modern fish, but were more like bony plates — rough, heavy and thick — making them a heavy, stiff fish. Also known as "spiny sharks," they had stout spines on their fins that were whitish and very rigid, almost like bony spikes. These spines reinforced their fins, which were fixed in place and non-movable like a shark's dorsal fin.
The Fins Have It: Acanthodians were only 6-12 inches long. The dorsal fins and the very last fin on the bottom (the anal spine) were single fins unlike all of the other fins, which were paired. Acanthodians had a cartilaginous skeleton, but their fins had a wide, bony base. Like most early fishes, acanthodians had tail fins with short bottoms and longer tops. They also had moderately large eyes that were placed forward on their rounded heads. |
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As seen in ANIMAL ARMAGEDDON:
Episode 1 — "Death Rays"
 Watch a Video of Acanthodian.
COULD YOU SURVIVE? Take the "Staying Afloat in the Age of Sea Creatures" Quiz to find out.
Acanthodian: CUTE or CREEPY? Rate its fright factor in Prehistoric Scary or Not?
Curious about fish in general? Visit our partners at HowStuffWorks.com to find out how fish work. |
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