Fish started appearing in thebeginning of the Paleozoic era.The first of the armored fishstarted in the Ordovician throughthe Devonian and they ruled theworld during that time. Fishstarted out as cartilaginous andlater developed a bone skeleton.
The world was completely coveredin water in the Paleozoic. Shallowseas covered what now areOhio, Kansas and other greatplain countries in the U.S. Theseshallow seas left well preservedfossils for us to excavate later.
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.
The Sacabambaspis appeared 510million years ago in the middle of theCambrian. Sacabambaspis had a bonyplate on the outside of theircartilaginous body. Their armor coveredtheir head and upper torso exposingtheir back half which was made up ofcartilage.
Sacabambaspis had scratches and piecesknocked out of their armor from predators orrough terrain. One of the predators thatcaused these scratches and dents was theEurypterid (sea scorpion). The jaw was non-existent at this time, the Sacabambaspis werefilter feeders. Their mouth was located eitheron the bottom or the front of their head. Fishsuch as the Sacabambaspis did not have finsto flap their way through the water, but wereeel like and swam in an “S” motion.
During the Ordivician, a bony vertebralcolumn began to appear in fish. The fishbegan to have complicated structures. Thesuspected cause for rapid evolution is themovement and placement of the continents.In the beginning of the Devonian nearly allOstracoderms were wiped out.
Other fish began to show up in hugequantities after most of the Ostracodermswere gone. This massive amount of fish gavethe Devonian it’s name, “The Age of Fish”. Placoderms arrived during the Silurian andthe 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!!!)
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.
The world in the Devonian period Gondwana, Euramerica and Siberia
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.
The Auctorrisus had no predators so mostpeople think that the armor was useless, butscientists think that they were cannibals. TheDunkleosteus armor was over 2 inches thick.Unfortunately they only lasted 50 millionyears and they branched off to many differentspecies around the world.
Labyrinthodont were giant amphibiansdistantly related to newts and salamanders.In outward appearance Labyrinthodontlooked much like modern salamanders, butwith two main differences; they had jawsfull of sharp teeth; and they often grew toenormous sizes. The smaller Labyrinthodont ate insects andfish, but the bigger ones sometimes atelarger animals.
The many sharp teeth they had wereuseful for catching such things as fishand perhaps unwary small dinosaursthat got too close to the water’s edge.But when the teeth of one good-sizedLabyrinthodont called Siderops kehliwere carefully examined, all that wasfound were the fossilized remains ofmillipedes and a piece of the backboneof another Labyrinthodont, meaningthey were cannibals.
It had a large head and powerful teeth, buthad a relatively weak body so it hunted foodunderwater, and ate land animals at thewaters edge, much like a crocodile would. Tocapture small prey in the water, all it neededto do was to open its mouth, and the rush ofwater would have sucked prey straight in.Strange enough, it’s teeth indicate thatLabyrinthodont was not content on sucking upsmall prey.
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.
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.
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/extinctio n/permass.html>Burton, Virginia. Life Story. Burton Virginia, 1962