Evolution of the Ostracoderms

From the Cambrian to the Permian

Fish started appearing in the beginning of the Paleozoic era. The first of the armored fish started in the Ordovician through the Devonian and they ruled the world during that time. Fish started out as cartilaginous and later developed a bone skeleton.

Intro

The world was completely covered in water in the Paleozoic. Shallow seas covered what now are Ohio, Kansas and other great plain countries in the U.S. These shallow seas left well preserved fossils for us to excavate later.

About the Paleozoic

Name: Group Name: Ostracoderms (shell- skinned) Scientific Name: Cartilago-anguilla (cartilage eel) Common name: Sacabambaspis

Length: Average of 30 centimeters long.

Behaviors: The Sacabambaspis could withstand most attacks because of it’s strong armor. It also could camouflage.

Traits: The Sacabambaspis was an algae sucker and it’s predator was the Eurypterid (Sea scorpion).

Climate: The land was very barren and hot on land.

Basic Info

The Sacabambaspis appeared 510 million years ago in the middle of the Cambrian. Sacabambaspis had a bony plate on the outside of their cartilaginous body. Their armor covered their head and upper torso exposing their back half which was made up of cartilage.

About the Ostracoderms

Sacabambaspis had scratches and pieces knocked out of their armor from predators or rough terrain. One of the predators that caused these scratches and dents was the Eurypterid (sea scorpion). The jaw was non-existent at this time, the Sacabambaspis were filter feeders. Their mouth was located either on the bottom or the front of their head. Fish such as the Sacabambaspis did not have fins to flap their way through the water, but were eel like and swam in an “S” motion.

Kingdom: Animalia Super Class: Agnathans Phylum: Chordata Subphylum: Vertebrata Class: Cephalaspidomorphi Order: Petromyzontiformes Family: Petromyzontidae

Taxonomy

(Camouflaged form)

Sacabambaspis

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(Sea scorpion)

Predator of the Sacabambapis

Eurypterid

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The PlacodermsLeaping to the Next evolution

During the Ordivician, a bony vertebral column began to appear in fish. The fish began to have complicated structures. The suspected cause for rapid evolution is the movement and placement of the continents. In the beginning of the Devonian nearly all Ostracoderms were wiped out.

Why did the Sacabambaspis Evolve?

Other fish began to show up in huge quantities after most of the Ostracoderms were gone. This massive amount of fish gave the Devonian it’s name, “The Age of Fish”.

Placoderms arrived during the Silurian and the Devonian replacing the Ostracoderms.

Name: Group name: Placoderms (Armor Skinned) Scientific name: Auctorrisus (Powerful

Bone) Common name: Dunkleosteus

Length: Up to 33 feet long

Weight: 4 tons (that’s the weight of 4 elephants!!!)

Basic Info

During the Devonian, there were two continents, Gondwana and Euramerica, located close to each other. A ocean covered the rest of the globe, and the land was completely dry. The climate was relatively warm and dry. There were no glaciers until the Late Devonian, when ice began to cover parts of the South Polar region.

About the Devonian

Gondwana, Euramerica and Siberia

The world in the Devonian period

The armor of the Auctorrisus covered their entire head and some of their body. Dunkleosteus had armor surrounding their eyes and had functional jaws unlike the Sacabambaspis. The Dunkleosteus did not have “teeth” but had bone extrusions that connected to the skull. It’s powerful bite had 11,000 pounds of strength and if the knives in it’s month concentrate that strength in a little point of the front it would with an amazing strength of 80,000 pounds per square inch. The Great White Shark, only could bite with half of this strength.

About the Placoderms

The Auctorrisus had no predators so most people think that the armor was useless, but scientists think that they were cannibals. The Dunkleosteus armor was over 2 inches thick. Unfortunately they only lasted 50 million years and they branched off to many different species around the world.

The Dunkleosteus

Auctorrisus

Comparison between the jaw of the Ostracoderms and the Placoderms

Ostracoderms Placoderms

Kingdom: Animalia Phylum: Chordata Class: Chonrichtyes Order: Rajiformes

Taxonomy

The Labyrinthodont

The Dawn of the Amphibians

There was a mass extinction in the Devonian and almost all Dunkleosteus were killed. To adapt to the dramatic changes the water, they evolved into amphibians and roamed on land.

Why did the Dunkleosteus evolve?

Name: Group name: Crocodilian (crocodile) Scientific name:Errordentium (maze of

teeth) Common name: Labyrinthodont (maze of

teeth) Length: Average 15 feet (head to tail)

Basic Info

The climate in the Carboniferous was very hot and humid. The first forests started to appear. In the Carboniferous there were lots more continents developing.

About the Carboniferous

World in the Carboniferous

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Labyrinthodont were giant amphibians distantly related to newts and salamanders. In outward appearance Labyrinthodont looked much like modern salamanders, but with two main differences; they had jaws full of sharp teeth; and they often grew to enormous sizes.

The smaller Labyrinthodont ate insects and fish, but the bigger ones sometimes ate larger animals.

About the Labyrinthodont

The many sharp teeth they had were useful for catching such things as fish and perhaps unwary small dinosaurs that got too close to the water’s edge. But when the teeth of one good-sized Labyrinthodont called Siderops kehli were carefully examined, all that was found were the fossilized remains of millipedes and a piece of the backbone of another Labyrinthodont, meaning they were cannibals.

It had a large head and powerful teeth, but had a relatively weak body so it hunted food underwater, and ate land animals at the water's edge, much like a crocodile would. To capture small prey in the water, all it needed to do was to open its mouth, and the rush of water would have sucked prey straight in. Strange enough, it’s teeth indicate that Labyrinthodont was not content on sucking up small prey.

Kingdom: Animalia Phylum: Chordata Class: Anphibia Order: Caudata

Taxonomy

Labyrinthodont

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It’s Hunting

Labyrinthodont

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The Mass ExtinctionThe Death of them all

You might be wondering, what happened to the Labyrinthodont between the time they evolved and the mass extinction? The answer is nothing. The Labyrinthodont did not have a reason to evolve, so they stayed the same.

What happened to the Labyrinthodont before the Mass Extinction?

The mass extinction wiped out 90-95% of marine animals. This was it’s main diet and was the only thing that young Labyrinthodont eat and adults also ate fish. The lack of food caused all Labyrinthodont to die out.

The Mass Extinction

Time Line

Works Cited Arreola, Freddie. “The Evolution of Armored Fish”. Cochise College Geology . Weller, Roger. Spring 2005. October 2011 <http://skywalker.cochise.edu/wellerr/students/armored-fish/armored-fish.htm>

“Labyrinthodont”. JoyZine. 2009. November 2, 2011 <http://www.artistwd.com/joyzine/australia/articles/dinosaurs/labyrinthodont.php>

“The Permian Mass Extinction”. Park. November 7, 2011 <http://park.org/Canada/Museum/extinction/permass.html>

Burton, Virginia. Life Story. Burton Virginia, 1962