Era Paleozoica

The Paleozoic Era:
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By:
Owen Connelly
Ivan Cortés
Ignacio Alvarez
Hans Jetter
Jaime Fullana


The Paleozoic, better named the Pelaeozoic, from the Greek palaios which means “ancient life” era was the earliest of the three eras that composed the Phanerozoic eon. It lasted from 542 to 251 million years ago approximately and is subdivided into the following six periods from oldest to youngest: the Cambrian period, the Ordovician period, the Silurian period, the Devonian period, the Carboniferous period and the Permian period.



The Cambrian Period:

The Cambrian Period is the first period in the Paleozoic era.. Cambrian is a period of time in Earth's history, which spanned from about 570–510 million years ago. The Cambrian is divided in the Terrenuivian, the Cambrian Epoch 2, Middle Cambrian and the Furongian Epoch. The name Cambrian is a name derived from the Roman name for Wales, which was Cambria. Wales was the original study location for sedimentary rock formed during this interval of Earth history from 570-510 mya. The term Cambrian was first used in 1835 by Professor Adam Sedgwick (1785–1873) of Cambridge University, who was studying the lower part of what was then called Transition strata which are the oldest known sedimentary rocks in Wales a layer of rock that corresponds to the Cambrian period.
During the time before the Cambrian period, known as the Vendian Period the continents were joined in a single supercontinent called Rodinia (from the Russian word for "homeland", rodina). As the Cambrian began, Rodinia began to fragment into smaller continents, which explains the unfamiliar concentrations and locations of the Earth’s landmasses seen in the map below.The Cambrian globe was concentrated in the southern hemisphere. The largest landmass (lower right) was “Gondwana” (a collection of today's southern continents). The second largest continent, “Laurentia” is just left of center in the map and includes most of North America (the southeastern US can be seen wedged between Africa and South America as part of Gondwana). Between Gondwana and Laurentia lie “Siberia” (just south of the equator) and “Baltica” (Scandinavia, Eastern Europe, and European Russia). The rest of Europe and much of what is today Asia still lay in fragments along the north coast of Gondwana.
During the Cambrian period the Earth in was when Earth first supported an oxygen-rich atmosphere similar to the one we breathe today the with the biggest difference being that the land was devoid of plants and animals, although there was life in the ocean, mainly in the form of plankton, sea sponges, and trilobites. This possibility of an oxygen rich atmosphere was the result of upheavals in the earth's crust which initiated a kind of reverse-greenhouse effect about 500 million years ago that cooled the world's oceans, spawned giant plankton blooms, and sent a burst of oxygen into the atmosphere. This then lead to an event known as the Cambrian Explosion. The theory of the Cambrian Explosion holds that, beginning some 545 million years ago, an explosion of diversity led to the appearance over a relatively short period of 5 million to 10 million years of a huge number of complex, multi-celled organisms. This consequently led to an incredible diversification of multicellular animals having many different body plans, including most of the major groups alive today, such as mollusks, trilobites, other arthropods, brachiopods, echinoderms, corals, sponges, and chordates. Also the Cambrian Period saw the first shelled animals of these the most iconic of which the Trilobites and the Anomalocalids which were the dominant predator of the time. These organisms are also part of, the oldest-known New Zealand fossils, which predate 508 million years ago. In which paleontologists found sponges, brachiopods, mollusks, conodonts and trilobites within limestone. Also it’s important to note that during this period, since life centered on the oceans the flora was composed mostly of fungi and algae since there were no land plants due to the atmospheric conditions in the surface. Finally there are accounts of a total of four mass extinctions, which occurred during the course of the Cambrian of which exists two current accepted hypotheses.
The first of which is Glaciations in the early Ordovician. The Glacial cooling hypothesis states that continental glaciations at the Cambrian-Ordovician boundary are responsible for a decrease in global climatic conditions. Such a decline in temperature would cause the destruction of Cambrian fauna, which are intolerant of cooler conditions, producing a mass extinction of mostly warm water species.
The other widely accepted hypothesis attributes the extinction to the Cooling and depletion of oxygen in marine waters. The hypothesis states the following, cooling and oxygen depletion would occur when cool waters from deep zones of the ocean spread up onto the continent, eliminating all organisms not able to tolerate cool conditions. The cooling would also result in stratification of the water column. Thus, species would ultimately perish due to their inability to tolerate dramatic shifts in such limiting factors as temperature and oxygen availability. Still further research is required to more fully test the validity of the above outlined Cambrian extinction hypothesis.













The Ordovician period:

The Ordovician period was named after the Ordovices, an ancient tribe in Britain who dwelt in the Welsh Borderland where rock strata of this period occurred. This period began, roughly, 492 million years ago after the Cambrian period and lasted about 57 million years with the beginning of the Silurian period. The Ordovician period is better known for its biodiversity in marine life.



The atmosphere in this period was very different in terms of the temperatures of different parts of the world. But first, according to paleontologists, carbon isotope measurements from preserved Ordovician soils demonstrate that the levels of carbon dioxide in that time was 14 to 16 times higher than today. This was caused by much volcanic activity, which released large volumes of carbon dioxide into the atmosphere. Also the many occurrences of flooding on the continents due to high sea levels and then low, would have suppressed the weathering of silicate rocks, a major mechanism from removing carbon dioxide to the atmosphere. And because of this, something like a greenhouse effect, these high levels of carbon dioxide in the atmosphere would cause temperatures to rise anywhere in the planet, from the Poles to the Equator. The climate during this period was fairly warm. Later the Gondwanaland continent moved to the south pole, where many scientists believe, that occurred a paradox since the Gondwanaland area at the south suffered glaciations, but this was due to that a sudden drop in the quantity of carbon dioxide in the atmosphere. Also some tectonic activity occurred, such as the sea floor spreading and ridge activity that was also combined with volcanic activity. Also ocean currents changed as a result of lateral continental plate motions causing the opening of the Atlantic Ocean, this also caused global underwater sea levels to transgress and regress.



There was a catastrophic extinction that occurred in this period. This extinction is known as the 2nd most devastating extinction that affected the marine communities in Earths history and the third largest of the five that affected Earths organisms in terms of loss of life.. The theory by scientist as to how this extinction occurred was the glaciations of the supercontinent Gondwanaland at the very end of the Ordovician period. Scientist believe that the cause of this glaciations was that around the time of the Ordovician period the global climatic cooling occurred to such a high level that there was a global large-scale continental resulting in a widespread glaciations around the time that Gondwanaland passed through the south pole. This also caused a chain event that caused the lowering of the sea level worldwide since large areas of water became frozen in tied up sheets of ice. So the combination of the lowering of the sea level and this rapid cooling because of the glaciations are what might have caused this extinction. This mass extinction was responsible for the disappearance of one third of all bryozoans and brachiopod families. Also a large number of groups composed of conodonts, trilobites and graptolites. Approximately hundreds of families of marine invertebrates became extinct because of the event.



In terms of the fauna during the Ordovician, most of it was found in the water. Something that is important is that the trilobites did not die out with the mass extinction from the Cambrian period. There was also a broad diversity of these trilobites and of conodonts(pohsphatic fossils with some tooth-like appearance). There where many diverse corals, because of fossils found, but the reef ecosystems in the oceans was dominated by algae and sponges, and also by bryozoans ( a moss like animal).The more important species in the Ordovician period where the Cephalopods which became the dominant species. There were other important invertebrates of this period such as the Brachiopods and the Crinoids. The Brachiopods, which mostly resemble a clam, but are not in the same family. Crinoids were an echinoderm that looked like a feathery plant, these organisms grew long stems and attached themselves to the ocean floor and these stems floated in the water and caught the food. The flora in the water was mostly green and red algae. An important discovery of the Ordovician period is that on the bottom of the seas were the animals that first grew backbones that were a bit primitive and these became the most important animal group in the ocean. An example of these is the ostracoderms, the jawless and armored fish that was very famous of this time. And lastly an important event that occurred during the Ordovician period was the appearance of the first land plants. These first plants were actually where bryophytes and mosses that were the evolution of groups of algae. These plants need environments with water so that the water flowed in and out of their veins. The problem was that these plants had no veins for the movement of the water inside of their bodies, and so the water had flow between the outside environment and the cells of the plants. Which finally lead to the first true plants because they contained chlorophyll and could make their own food.


Dominant species:

There was a dominant species, better said predator and these were the Cephalopods. These are a group of mollusks that are related to the squid and the octopus. The genus was diverse and was found on almost all the seas of the Ordovician period. These were the dominant species because most of the marine life in the Ordovician was small, while the Cephalopods were bigger, faster because of the structure of their body, and had advanced vision. An important feature of the Cephalopods was that they developed bigger brains and better senses.

Evidence of fossils and location:

The evidence found to prove the Ordovician period was the one found on the shallow Canning Basin in northwestern Australia. During the Ordovician what is now Australia was located at the equator. The environment today is desert, but evidence suggests that the basin was a deep-water marine environment with high level of faunal activity. The fossils that were found in this basin were the gastropods. In the Emanuel formation, south of the Canin Basin, there were found 130 specimens, which included six different species in five different genera.

Map of the land and continents during the Ordovician period:




Gondwanaland where most of life was found and where the Ordovician mass extinction occurred.



The Silurian Period:
The Silurian (443 to 417 million years ago) was a time when the Earth underwent considerable changes that had important repercussions for the environment and life within it. The Silurian Period began with the following o a melting of large glacial formation that caused the rise of ocean levels. Coral reefs made their first appearance during this time, and the Silurian period was a great time of the evolution of fishes. During this period the jawless fish was still present, but they evolved into fishes with jaws and freshwater fishes. It is also at this time that our first good evidence of life on land is preserved, including relatives of spiders and centipedes, and also the earliest fossils of vascular plants. The Silurian period is divided into four epochs (from oldest to youngest): the Llandovery, the Wenlock, the Ludlow, and the Pridoli. Each epoch is distinguished from the others by the appearance of new species of graptolites. Graptolites are a group of extinct colonial, aquatic animals that put in their first appearance in the Cambrian period (543 -490 million years ago) and persisted into the Early Carboniferous (354-290 million years ago). The beginning of the Silurian (and the Llandovery) is marked by the appearance of Parakidograptus acuminatus, a species of graptolite.
The Llandovery (443-428 million years ago) preserves its fossils in shale, sandstone, and gray mudstone sediment. Its base (beginning) is marked by the appearance of the graptolites Parakidograptus acuminatus and Akidograptus ascensus. The Llandoverian epoch is subdivided into the record of the Wenlock was the conodont Pterospathodus amorphognathoides Rhuddanian, Aeronian, and Telychian stages. At the close of the Telychian stage, the appearance of Cyrtograptus centrifugus marks the start of the Wenlockian epoch (428-423 million years ago). The fossils are found in siltstone and mudstone under limestone. Missing from the fossil, present in earlier strata. This is an epoch with excellent preservations of brachiopod, coral, trilobite, clam, bryozoan, and crinoid fossils. The Wenlock is subdivided into the Sheinwoodian and Homerian stages.
The Ludlow (423-419 million years ago) consists of a siltstone and limestone strata, marked by the appearance of Neodiversograptus nilssoni. There is an abundance of shelly animal fossils.
Platy limestone Gorstian and Ludfordian stages make up the Ludlow epoch. strata rich in cephalopods and bivalves characterize the Pridolian (419-417 million years ago), the final epoch of the Silurian. It is marked by the appearance of the index fossil Monograptus parultimus, and also by two new species of chitinozoas (marine plankton), Urnochitina urna and Fungochitina kosovensis, which appear at the base or just above the base of the Pridoli.
The climate of this period was consisted of the increasing warmth in the earths surroundings.
With the increase of water levels came the new era for new species. Following the Ordovician extinction event there was a rapid recovery of invertebrate faunas during the Silurian. The high sea levels and warm shallow seas provided a safe environment for marine life of all kinds. The biota and ecological dynamics were basically still similar to that of the Ordovician, but was more diverse
Branchiopods are the most common hard-shelled organisms, making up 80% of the total species. Among these, pentamerids first appear and are abundant, rhynchonellids, and the spire-bearing athyridids and atrypidids are also common, as are other groups that continue from the Ordovician.
Tropical reefs are also very common in these shallow seas of this period, formed by tabulate and rugose corals, stromatoporoid organisms, bryozoa and calcareous algae. The Trilobites, having reached their peek in the Cambrian and Ordovician, are now dying out. The trinucleids and asaphids are absent, whilst encrinites and illaenids do not survive the end of the Silurian
Planktonic graptolites remain common and diverse. The single-spined Monograptus is the predominant genus, and its species are useful as zone fossils.
The Jawless fish appeared in the brackish and fresh water, as do eurypterids, xiphosurids, scorpions, which it is considered to have been semi-aquatic. rhyniophytes, primitive lycophytes, and myriapods became the first proper land organisms. At the end of the period Jawed fish appeared for but remained unimportant and didn’t change until later on in the Devonian period.


Map of the Silurian periods land and water areas:










The Devonian period
It takes its name from the word Devon, from England meaning the “Age of Fish”, it’s the period that follows the Silurian period and it is associated with it. The Devonian period was recognized for its mass evolution of plants from small, leafless and seedless to the first forest of all history. It was also viewed for its distinct marine reef builders who build large complex reef, there was also evolution in sea, in the early Devonian period all the fish species were jaw less and small, defend less, but at the late Devonian period came the first jawed and very predatorily fishes like sharks that were very huge in those times. The sea in the Devonian period is a very interesting concept, even though there was large activities of evolution there was also a mass extinction that affected only the marine species, especially reef builders, the trilobites species and jawless fishes. One of the most interesting things of the Devonian period is its mass extinction; there are two theories of this mass extinction that was composed of the disappearance of all reef-building activities of life.
The Devonian seas were dominated by branchiopods, such as the spiridferids, and by tabulate and rugose corals, which built large bioherms, or reefs, in shallow waters. Red algae also contributed to reef building. In the Lower Devonian, ammonoids appeared, leaving us large limestone deposits from their shells. Bivalves, crinoids and blastoid echinoderms, graptolites, and trilobites were all present; though most groups of trilobites disappeared by the close of the Devonian.
The Devonian is also notable for the rapid diversification in fish. Benthic armored fish were very common by the start of the Devonian period. These early fish are collectively called "ostracoderms", and include a number of different groups. By the Mid-Devonian, placoderms, the first jawed fish, appeared. Many of these grew to large sizes and were feared predators. There was also the start of the first sarcopegyniian, or the lobe-finned fish, which eventually produced the first tetrapods just before the end of the Devonian period.

By the Devonian Period, life was in the mist of the colonization of the land. Before this time, there was no appearance of organic life in the soil, causing these soil deposits to be a reddish color. This is indicative of the underdeveloped landscape, probably colonized only by bacterial and algal mats.
By the start of the Devonian, however, early terrestrial vegetation had begun to spread. These plants did not have roots or leaves like the plants most common today, and many had no vascular tissue at all. They probably spread largely by vegetative growth, and did not grow much more than a few centimeters tall. These plants included the now extinct zosterophylls and trimerophites. The early faunas (animals) living among these plants were primarily arthropods: mites, trigonotarbids, wingless insects, and myriapods, though these early faunas are not well known.
By the Late Devonian, lycophytes, sphenophytes, ferns, and progymnosperms had evolved. Most of these plants have true roots and leaves, and many are rather tall plants. The progymnosperm Archaeopteris, whose leaves are shown at right, was a large tree with true wood. In fact it is the oldest such tree known, and produced some of the world's first forests. By the end of the Devonian, the first seed plants had appeared. This rapid appearance of so many plant groups and growth forms has been called the "Devonian Explosion". Along with this diversification in terrestrial vegetation structure, came a diversification of the arthropods. All this was caused by the climate change, which had to do with the movement of tectonic plates that joined in the equator, this made the climate warmer. It caused plants to evolve and take energy from the sun, the first forest was created and the first seeds as well. But the movement of the tectonic plates will also cause the mass extinction that made the Devonian period so famous and interesting.
Evidence supporting the Devonian mass extinction suggests that warm water marine species were the most severely affected in this extinction event. This evidence has lead many paleontologists to attribute the Devonian extinction to an episode of global cooling, similar to the event, which is thought to have caused the late Ordovician mass extinction. According to this theory, the extinction of the Devonian was triggered by another glaciations event on the Appalachian Mountain Range which contained the tectonic plates of USA and Europe that collided and formed the Appalachian mountains which was called the Euramerica movement similar to the Gondwana which was made up by the tectonic plates from south America, Africa, Antarctica, India and Australia forming into the giant continent. These huge continents were sometimes called the Old Red Continent”. Also these two huge continents were drifting north forming a huge gap of water now called the Pa As evidenced by glacial deposits of this age in northern Brazil. Similarly to the late Ordovician crisis, agents such as global cooling and widespread lowering of sea-level may have triggered the late Devonian crisis. As the land species were enjoying their new warm, comfortable climate the marine species that were warm marine species were experiencing temperature cooling in the waters, also with the movement of the tectonic plates the reefs were wiped out. More evidence could not be found, fossils disappeared and there is still no real theory of what caused this mass extinction.




Land water divisions during the Devonian period:





The Carboniferous Period:
The Carboniferous Period is located in the Geologic Time Scale in the Paleozoic Era, before Permian Period and after the Devonian Period, 360 million years ago to 286 million years ago.
The name “Carboniferous” comes from England, where geologists William Conybeare and William Phillips proposed it in 1822. The name makes reference to all the rich deposits of coal found in this period. This Period has been divided in the United States in two, Mississippian (Lower Carboniferous) and Pennsylvanian (Upper Carboniferous). The division is for the geologists to distinguish from the Pennsylvanian coal bearing layers and the Mississippian mostly limestone layers. The Carboniferous Period is famous for the vast quantity of swamps, which produced coal and thus the name “coal-bearing” Carboniferous comes.
World Map at the time:

On the first part of the period, it was mostly warm but there was a cooling and glaciations moment during the second half, which was caused due to Gondwanaland’s southward migration. The equatorials regions remained warm and wet, tropical while the poles were in a massive ice age, one that lasted for many millions of years. During the first half of the period, an explosion of terrestrial plant life accompanied the warm tropical weather. During the second half of the period the climate had become increasingly drier and colder. By the time the Permian Period arrived, the temperature had declined to 10° C. There was also a large ice cap formation especially in the southern hemisphere. During the Carboniferous Ice Age, the alternating warm and cold temperatures coincided with cycles of expansion and retreat of glaciers. Coastlines fluctuated due to worldwide sea level changes.

As mentioned before, the Carboniferous Ice Age is the most notable climate process that occurred besides slight movements of the tectonic plates. The coal swamps that formed the rich coal deposits. Geologically, the Late Carboniferous collision of Laurussia (present-day Europe and North America) into Godwanaland (present-day Africa and South America) produced the Appalachian mountain belt of eastern North America and the Hercynian Mountains in the United Kingdom. A further collision of Siberia and Eastern Europe created the Ural Mountains.

Catastrophes or Extinction that affected organisms:
As mentioned before, the Carboniferous Ice Age is the most notable climate changed and it did affect the organisms that lived there.

Fauna: During the Carboniferous Period diversity in the animals once again increased. This Era is marked by the Sea Animals. These Sea Animals are mostly what we call today corals, as shown in the table in the left. The other type of Sea Animals is what we call today shrimps, crabs, lobsters, shells, barnacles and fishes. Called then were the eurypterids, ostracodes and trilobites. In land were mostly spiders and cockroaches, insects mostly.

Flora: During the Carboniferous life flourished mostly on sea in the oceans by the coral reefs and fishes. In land there were forests as well as the “trademark” of the Carboniferous period, swamps. Oxygen levels were higher during this time than at any other time in the history of the Earth. Mostly, the weather was tropical except in the pole (south) were it was covered by ice.

The Dominant species of this period is the Greererpetron, a large carnivorous that lived in rivers and swamps; it was shaped like an eel and a crocodile. But the largest hunters of the time were the gigantic rhizodont fish, reaching 7 meters in length.
The Carboniferous-Permian boundary is distinguished by the appearance of the fusulinid foram Sphaeroschwagerina fusiformis in Europe and Pseudoschwagerina beedei in North America. The stratigraphy of the Lower Carboniferous is distinguished by the shallow-water limestones. These limestones are composed of parts of organisms, mostly the remains of crinoids. These thrived in the shallow seas of the Lower Carboniferous. Other limestones include lime mudstones and oolithic limestones. Lime mudstones are composed of the carbonate mud produced by green algae. Oolithic limestones are composed of calcium carbonate in concentric spheres that were produced by high wave energy. Sandstones (sedimentary rock composed of quartz sand and cemented by silica or calcium carbonate) and siltstones (rock composed of hardened silt) are also found in the Lower Carboniferous strata, though not in as great abundance than the limestones. Coal beds, which can be up to eleven to twelve meters thick, characterize the Upper Carboniferous. The type localities for the Mississippian Period are Kinderhook, Illinois; the Meramec River, southeastern Michigan; and the Chester district, southwestern Illinois. All three type localities are in the upper Mississippi Valley. Other type localities for the different series within the Mississippian Period occur throughout Europe and North America, some of which are the Avon Gorge section in Bristol, England and the Pocono Group in the Appalachian region of North America. The type locality for the Pennsylvanian Period occurs in central West Virginia in the United States. Others occur in the Jackfork and Johns Valley shales of Oklahoma and Arkansas and the Supai Group in the Grand Canyon. In Europe the type localities for the Upper Carboniferous include the Millstone Grit and the Coal Measures in England.

The Permian period:

Ubicar en la escala de tiempo geológico su era.
299 to 251 million years ago

Permian period was named in 1841 by the geologist Murchison after a tour he had on the Imperial Russia. He named it after the ancient kingdom of Permia and the present city of Perm near the Ural Mountains.

Presentar un mapa del globo terráqueo de cómo estaban las masas continentales para ese tiempo



The atmosphere changed as the Permian opened, the Earth was still in the grip of an ice age, so the Polar Regions were covered with deep layers of ice. Glaciers continued to cover much of Gondwanaland. At the same time forests covered the tropics. Towards the middle of the period the climate became warmer, the glaciers receded, and the continental interiors became drier.


There was indeed extinction in the Permian. It was the Permian–Triassic (P–Tr) extinction event, informally known as the Great Dying, was an extinction event that occurred 251.4 million years ago, forming the boundary between the Permian and Triassic geologic periods. It was the Earth's most severe extinction event, with up to 96 percent of all marine species and 70 percent of terrestrial vertebrate species becoming extinct; it is the only known mass extinction of insects.


There was a diversity in fauna and flora. Sedentary organisms like stromatolites, algae, foraminifers, sponges (, corals, bryozoa, and brachiopods, built great reefs which in turn provided homes and shelter for active animals like ammonoids, nautiloids, gastropods and fish. This was a period of transition. The early Permian saw the continuation of the Carboniferous biomes, with polar tundra regions and warm wet tropical swamp forests. But the drying climatic tendency during the mid Permian spelled death for the swamp forests. For example, water plants like Lycopsida and Sphenopsids were greatly reduced in size. The old tropical coal swamps disappeared with the drier and cooler climate, surviving only in China and in high latitudes of Pangaea. Plant life consisted mainly of ferns and seed-ferns, with new plants like conifers and ginkgos coming into prominence.


Reptiles grew to dominance among vertebrates, because their special adaptations enabled them to flourish in the drier climate. In this group you could find large reptiles such as dimetrodon. Dimetrodon - ancestor of the mammals belonged to the family called Pelycosaurs, which had both mammal and reptile characteristics. Dimetrodon was a dominant carnivore, the largest one of the Permian period.


as a significant discovery of Dimetrodon footprints in southern New Mexico, USA, by Jerry MacDonald.

References in APA format


Ordovician Period. (2009). In Encyclopedia Britannica. Retrieved October 21, 2009, from Encyclopedia Britannica Online: http://www.britannica.com/EBchecked/topic/431581/Ordovician-Period

Mann, D., & Mann, C. (2005, April). The Ordovician Period. Retrieved from : http://www.fossils-facts-and-finds.com/ordovician_period.html

Waggoner, B., & Collins, A. G. (1994, November 22). The Cambrian Period. Retrieved from http://www.ucmp.berkeley.edu/cambrian/camb.html

Kazlev, A. (2002, April 11). The Cambrian Period : 1. Retrieved from : http://www.palaeos.com/Paleozoic/Cambrian/Cambrian.htm

Gore, P. (1995, October). The Devonian Period. Retrieved from : http://facstaff.gpc.edu/~pgore/geology/geo102/devonian.htm

Geographic Society, National. (1996). Silurian Period. National Geographic, Retrieved from: http://science.nationalgeographic.com/science/prehistoric-world/silurian.html

Kazlev, A. (2002, April 11). The Permian Period : 1. Retrieved from : http://www.palaeos.com/Paleozoic/Cambrian/Cambrian.htm

Video organismos del Cambrico

Bienvenidos a nuestro Blog:

Los creadores de este blog somos , Ivan Cortes, Hans Jetter , Owen Connelly , Jaime Fullana y Ignacio Alvares.

Somos estudiantes en el Colegio San Ignacio de Loyola.
Este blog esta dirigido a la clase de Biologia de Undecimo grado y a nuestro projecto investigativo de la Era Paleozoica. El proposito de este blog es presentar de una manera accesible nuestro trabajo y frutos de nuestra investigacion sobre la era Paleozoica.

Esperamos que les venga de provecho su visita a este blog, gracias.