Lab2
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School
Texas A&M University *
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Course
207
Subject
Geology
Date
Apr 3, 2024
Type
Pages
9
Uploaded by ProfHyena4160
The Pangea Puzzle
Introduction One of the most fundamental questions we can ask in geology is how the continents that we see today got to be in their current configurations. Data on the distributions of organisms in the fossil record make it possible to identify where they lived in the past, and that data can be used to help identify past continental positions. To do this, paleontologists track the occurrence of fossil organisms, in other words where a species occurs in space (geographically) and when a species occurs in time (stratigraphically). The Paleobiology Database (PBDB, https://paleobiodb.org/navigator/
) is a huge online database that seeks to catalogue all fossil occurrences, across all geologic time, and across the whole tree of life. It’s the standard tool used by paleobiologists to track where fossil organisms lived and when. Delving into the Database Open the PBDB Navigator and spend some time getting comfortable with how it works: https://paleobiodb.org/navigator/ The Navigator consists of three parts: 1.
Map
(CENTER) showing continents with dots representing fossil occurrences. The color of these dots represents their geologic age. If you click on the dots, you can see all of the information on each site and the fossil species that occur there. 2.
Geologic time scale
(BOTTOM) showing the major eras, periods, and stages. If you click on the timescale, the map will show you the location of all fossil occurrences from that time interval. 3.
Tool bar
(LEFT) showing the tools you can use to explore the database. These include: zoom in/out on the map reconstructs plate tectonic configurations for time interval you are exploring narrow down which taxonomic group is plotted on map create a diversity curve for the occurrences currently plotted on map download the data (lat/long, geologic age, etc.) for the occurrences plotted on map Need help? Here’s a YouTube video to help you get started: https://www.youtube.com/watch?v=db2He3p-Jco
Goal:
Use fossil distributions to test the hypothesis that the modern continents were joined in Pangaea during the Late Paleozoic but largely separated in Mesozoic. Step 1: Construct maps of fossil distributions Lystrosaurus
is not a dinosaur. It is a genus of synapsid, and thus more closely related to mammals than to dinosaurs, that lived in the Late Permian to early Triassic. Reconstruction of Lystrosaurus murrayi.
Image by Dmitry Bogdanov CC BY-SA 3.0 via Wikimedia Commons
1.
Enter Lystrosaurus
in the search field and click enter. 2.
The dots on the map show where in the modern world paleontologists have discovered fossils of Lystrosaurus
. At this point, stop and consider your map. a.
Describe the locations of the fossil finds in terms of the continents and/or countries in which the fossil were found. (1 pt)
The fossils were found mostly in South Africa and a few in northwest China as well as Russia and India. 3.
The color of the dots on the map match those of the geologic time scale below, indicating the age of the fossils. You may need to zoom in a bit to get the dots to change to a specific color. a.
Based on this matching, during which geologic period did the majority of the Lystrosaurus
found live? (1 pt)
It appears that most of the Lystrosauruses found lived during the early Triassic period. 4.
Now, reconstruct the map at that time period by clicking on the name of the time period in the geologic time scale followed by the tool bar icon showing the continents on the left. Note that the map changes, moving the continents to their positions during the time period that you clicked. a.
Describe how the position of the fossil finds changed. Are they now closer together or further apart? (1 pt)
Most of the fossils are now a lot closer together than they were before. There are a few that are still in the north, but a majority are in the south. b.
Save a copy of your map for Lystrosaurus
and paste it on the fifth page of this lab (1 pts)
.
Repeat this process for Mesosaurus
and Glossopteris
. Mesosaurus
is also not a dinosaur. It is an extinct genus of aquatic reptile from the early Permian. Reconstruction of Mesosaurus
.
Image by Nobu Tamura CC BY-SA 3.0 via Wikimedia Commons
5.
Enter Mesosaurus
in the search field and click enter. (Be sure to clear out the information about Lystrosaurus
.) 6.
Look at the distribution for these fossils. a.
Describe the locations of the fossil finds in terms of the continents and/or countries in which the fossil were found. (1 pt)
The fossils were found in South America, specifically Brazil and Uruguay. There were also some found in South Africa and Nambia. b.
In what ways is the distribution of Mesosaurus
different from Lystrosaurus
? (1 pt)
The Lystrosaurus were a lot more spread out, even with the continent changes, while the Mesosaurus is mostly in the same area/the southern hemisphere. c.
Given the different ecologies of Mesosaurus and
Lystrosaurus, provide a well-reasoned explanation for why their distributions are different. (1 pt) The ecologies explain why their distributions are different because the Mesosaurus was an aquatic reptile while the Lystrosaurus was a land mammal. Since they lived in different time periods, the land around them was very different as well so they simply lived where they were best adapted to at their time. d.
How do you think this animal might have gotten distributed in this pattern? (1 pt)
The Mesosaurus most likely lived in one area during pangea, when all the continents were merged. Thanks to continental drift Pangea broke apart into the separate continents we now have today. Most likely West Africa and South America were one when the Mesosaurus lived. 7.
Click on the time period on the geological time scale that represents when the majority of Mesosaurus fossils were found. e.
Describe how the position of the fossil finds changed. Are they now closer together or further apart? (1 pt)
The fossils are now much closer together and don’t have an entire ocean between them.
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8.
Save a copy of your map for Mesosaurus
and paste it on the fifth page of this lab (1 pts)
. Glossopteris
is a genus of seed ferns, and extinct group of plants that lived in Permian period. Image from OSU QM 270-16-B, Orton Geology Museum, Ohio State University, Columbus, Ohio, USA CC BY-SA 3.0 via Wikimedia Commons
. 9.
Enter Glossopteris
in the search field and click enter. (Be sure to clear out the information about Lystrosaurus
.) 10.
Look at the distribution for these fossils. f.
Describe the locations of the fossil finds in terms of the continents and/or countries in which the fossil were found. (1 pt)
The Glossopteris was very spread out and found on a lot of continents including southeast Africa, southern South America and southern Asia. There was also some found on Antarctica and around Australia. g.
In what ways is the distribution of Glossopteris
different from Lystrosaurus
? (1 pt)
The distributions of both were very different, the Glossopteris was much more spread out given that it was a plant while the Lystrosaurus was a land mammal mostly in one area. The Lystrosaurus also survived during the Permian and Triassic periods while Glossopteris is only found during the Permian. h.
Provide a well-reasoned explanation for there are so many more fossil occurrences of Glossopteris than Lystrosaurus
. (1 pt) Since the Glossopteris was a plant it most likely had a much easier time at reproducing and could spread a lot farther. The Lystrosaurus would have to find a specific mate, as well as food and water resources. The fossils for plants are also a lot more common since theyre less likely to be scavenged, and theres so much more of them.
11.
Using the data on the distribution of these three organisms from the Permian and Triassic as evidence, provide a well-reasoned argument for the claim that continents that are distant today where once consolidated into a supercontinent. (4 pts)
The continents that are distant today definitely used to be one large supercontinent. This is shown in the fossil record with how certain fossils are distributed in ways that don’t make sense when looking at our continents today. The Lystrosaurus fossils were very spread out, but when assuming the continents were once together they are actually more concentrated in specific areas. Paste your maps of Lystrosaurus
, Mesosaurus, and Glossopteris here.
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Part 3: Dinosauria after Pangea Let’s examine the distribution of some dinosaur genera that originated after the breakup of Pangea. For each genus, individually examine the modern maps check off the modern continents where fossils from each are found using the table. (2 pts)
12.
Describe the similarities and differences in the distribution of these genera using names of modern continents or countries. (2 pts) The tyrannosaurus and Hadrosaurus fossils are both found in North America as well as Asia. The Spinosaurus and Carcharodontosaurus have been found in South America (Brazil) and Africa, though they both have many more appearances in north Africa than they do in South America. 13.
Examine each genus individually on the Cretaceous paleogeographic map. How might the position of the continents explain the distribution of each these genera? (2 pts) The positions of the continents during the Cretacious period show that the fossils were actually once close together. It also shows what habitats these dinosaurs were living in as well as what resources they were most interested in like water or forests. 14.
Paste the Cretaceous maps for each genus on the next page of this lab. (2 pts)
15.
Does the data you collected in the lab support or refute the hypothesis that that the modern continents were joined in Pangaea during the Late Paleozoic but largely separated in Mesozoic? Provide clear evidence and reasoning to support your claim. (5 pts) The data does support the Pangaea hypothesis since you can see that certain fossils such as the Tyrannosaurs and Hadrosaurus were both discovered in North America and Asia. At first these fossils seem like their spread very far apart. When you assume the existence of Pangaea though, the fossils would have been close together at some point in time. Genus N. America S. America Asia Europe Africa Australia Antarctica Tyrannosaurs X X Hadrosaurus X X Spinosaurus X X Carcharodontosaurus X X
Paste your Cretaceous Dinosaur maps here
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