Hallucigenia.

Hallucigenia was a strange lobopod that probably fed on sponges, like Hazelia and Vauxia. The name is pronounced huh-loo-suh-JANE-ee-uh or huh-loo-suh-JEN-ee-uh.

Nobody knows what end of Hallucigenia was the head. Another thing that is mysterious is that no one knows if Hallucigenia swam or crawled. 

Hallucigenia had strange spines sticking out of its back. There was one row of spines on each side. Those spines could have been very useful because many predators fed on lobopods because they were so slow and small and soft. Most of them were almost defenseless. 

Dunkleosteus.

Dunkleosteus was a twenty-foot placoderm that lived in the late Devonian Period. It was the top predator. The name can be pronounced dunk-ull-AH-stee-us or dunk-lee-OH-stee-us or 

dunk-lee-AH-stee-us.

It ate everything from small fish to its own species. 

Credit: Jamie Chirinos/Science Photo Library

Like all placoderms, Dunkleosteus had its whole entire head covered in plates of armor. It had huge teeth that were probably somewhere around 3". Even its eyeballs were covered in armor. All that remains of Dunkleosteus is its head armor. 

Arthropleura.

Arthropleura was a seven-foot millipede that lived in the Carboniferous Period. The Carboniferous Period also had a lot of other giant arthropods. The name is pronounced arthro-PLEW-ruh.

Arthropleura could literally stand up, half of it pointing up in the air, and half of it on the bottom holding it up. Even though Arthropleura ate ferns and other plants, it did have strong mandibles that could really injure someone. 

The reason the giant arthropods were alive only in the Carboniferous Period is because the whole entire world was either ocean or a swamp. Swamps are usually known to have millions of plants, so imagine if the whole world was covered in a swamp. Then there'd be a lot of oxygen, because plants make oxygen. An arthropod would have trouble getting the oxygen to all its different parts if there wasn't enough oxygen, so all the oxygen would allow the arthropods to get very, very big. 

Helicoprion (Part 1).

There are a lot of different ideas about how Helicoprion might have looked. The "buzz saw" could have been in the jaw, and that's at least what I think. It also could have been anywhere on the entire body. Helicoprion lived Carboniferous to early Triassic. The name is pronounced hella-cuh-PRY-on.

The Helicoprion in the picture below may have helped it smash ammonite shells, or any other prey with a shell, including trilobites and other shelled animals. It may look like Sarcoprion, but Sarcoprion only has half a "buzz saw," and this idea of Helicoprion has a whole "buzz saw," but half of it is wedged into the inside of its jaw.

The Helicoprion in this last picture may have opened its mouth and let its "buzz saw" hang down while swimming through a school of fish. That way, it could kill many fish and easily just swim around in the school and eat freshly killed fish. 

My sketchbook.

Cephalaspis and Lanarkia.

Lego Cephalaspis

Lego Lanarkia spinosa