Dino lab 1
pdf
keyboard_arrow_up
School
Texas A&M University *
*We aren’t endorsed by this school
Course
207
Subject
Geology
Date
Apr 3, 2024
Type
Pages
6
Uploaded by ProfHyena4160
Modes of Preservation and Depositional Environments Part I: Fossil Identification and preservation There are numerous ways by which an organism may be preserved. The following are some of the more common modes of preservation:
Unaltered Body Fossil
•
Soft parts
- preserved given the slow rates or cessation of bacterial decay. •
Hard parts
- the skeletal material may be composed of calcium carbonate (calcite or aragonite), silica, calcium phosphate, or organic compounds Altered Body Fossils
•
Permineralized (petrified) - the process of filling in the spaces within the original material with inorganic mineral substances. It does NOT replace, but adds to, the original material. This process is common with plants and bones. •
Replacement
- the process of replacing the original biomineral or organic matter with a substance such as calcium carbonate, silica, or iron compounds. •
Recrystallization
- the process of changing the microstructure of the original biomineral and is caused by solution and reprecipitation of the material. The primary chemical composition of the shell is unchanged, but the mineral structure is changed. •
Carbonization (distillation)- the process involving the loss of the volatile constituents: oxygen, hydrogen, and nitrogen, leaving a carbonized residue. Concretionary Preservation •
Concretions
are hard, well-mineralized, portions of a sedimentary layer. They are often ovoid or spherical in shape and sometimes contain a fossil at their center. Because they are more resistant to erosion and compaction than the surrounding less-mineralized sedimentary rock, they can enhance the preservation of body fossils. Body Fossil Impressions
•
Molds
- impressions of the exterior surface (external mold) or interior surface (internal mold) of an entire organism or the portion of one. Both types make negative impressions of the objects (such as fingerprints in clay). The interior molds of closed shells are often called steinkerns. •
Casts
- formed by filling an external mold and duplicating the shape and ornamentation of the exterior of the original object. These may form from external molds or between external and internal molds. Trace Fossils
record the actions
and behavior
of an organism rather than a part of the organism itself. A single organism can make many different types of traces and similar looking traces can be made by different organisms that have similar behaviors. Thus, trace fossils are named and classified based on the behavior that made them rather than on the trace maker.
Part 1: Fossil Identification and Preservation (12 questions, 1 pt each) 1.
Dinosaur footprint: https://skfb.ly/KRU8
. Using the terms on first page, what type of fossil is this? Explain your choice. It is a trace fossil because its showing where the dinosaur walked. 2.
Internal mold of a gastropod: https://skfb.ly/FCPx
. Describe how this fossil could have formed. Most likely some kind of sediment got inside the original gastropod and hardened. Once the rest of the gastropod eventually decayed the sediment inside remained. 3.
Fossil seed fern: https://skfb.ly/6YHZS
. Using the terms on first page, what type of fossil is this? Explain your choice. This is a carbonization fossil because all the nutrients of the original leaves are now gone but it still left a carbon residue imprint on the stone. 4.
Mosquito in amber: https://skfb.ly/6xWCO
. Using the terms on first page, what type of fossil is this? Explain your choice. This is a soft body fossil since bacteria and decay couldn’t reach the mosquito and it remained whole.
It could also be carbonization since once the mosquito was in amber, oxygen hydrogen and nitrogen couldn
’
t get to it and it became carbonized. 5.
Therizinosaurus cheloniformis
https://skfb.ly/BXSQ
. Using the terms on first page, what type of fossil is this? Explain your choice. This is an unaltered hard body fossil because the original fossil has just become calcified and turned into stone. 6.
Permineralized wood: https://skfb.ly/6AMpB
. Examine the fossil and read the annotations. What features of the fossil allow you to recognize it as wood? The features of the fossil that make it recognizable as wood are the knots on the side as well as the growth rings inside.
7.
Dinosaur skin impression: https://skfb.ly/oHqGL
. Is this impression in positive or negative relief? Is this a mold or a cast? Describe how this fossil could have formed. It is in negative relief and is also a cast. This most likely formed from the dinos skin being imprinted into something like mud or clay and then more sediment filled in the impression in the clay leaving with the skin cast. 8.
Plesiosaur Bone Fossil: https://skfb.ly/6RwSD
. Examine the fossil and read the annotations. Describe how this fossil was preserved. It is preserved because of concretion. It is stuck inside of a sedimentary layer that’s
very well mineralized. 9.
Cephalopod: Gunnarites sp. (PRI 61543) https://skfb.ly/6RRsD
. Using the terms on the first page, what TWO types of fossil preservation does this specimen represent? Explain your choice. It is both a concretion and permineralization, because its enclosed in a rounded piece of sediment and the fossil inside has an interior & exterior imprint that most likely came from sediments filling in the pores of the rock. 10.
Dinosaur egg: https://skfb.ly/6YVAS
. The scale bar in the image is marked off in centimeters. Estimate the completeness of preservation. The completeness of preservation is around 5 centimeters. 11.
Petrified palm wood: https://skfb.ly/6V8r8
. Using the terms on the first page, describe how this fossil was preserved. This fossil was most likely replaced over time by silica or some other substance. 12.
Carcharodontosaur Tooth: https://skfb.ly/OLpA
. Examine the specimen. What do you notice about the edges of the tooth? The edges of the tooth are kind of bumpy/rough and some parts have broken off, it either means it was a carnivore or the tooth was weathered down before it became preserved.
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
Part 2: Depositional Environments and Fossil Preservation (13 total points) 1.
Examine these different dinosaur footprints below and the illustration of how dinosaur tracks preserve on the next page. Note the preservation of skin impressions in the right image. Think about the grain size of the sediment the dinosaur was walking across. 1a. Would skin impressions more likely be preserved if the true track was made in clay or sand? Explain your reasoning. (2 pt) The impressions would probably be more preserved in clay because clay has a lot finer grains and holds together better than sand would. 1b. Would you expect skin impressions be preserved in the natural cast and/or the undertrack? Explain your reasoning and the circumstances under which the skin impression would be preserved. (3 pts) Skin impressions can be preserved in the natural cast but it depends on the circumstances what sediment its in, as well as if its in an area where it can easily be destroyed or weathered. If the dinosaur were to step into something like clay or mud, that clay/mud would eventually dry up and harden leaving the impression and forming a cast, if it is left undisturbed for long enough. An undertrack probably wouldn
’
t show skin unless the dinosaur stepped down super hard into something soft.
True tracks, natural casts, undertracks, and track infills are all types of fossil tracks that can be created from a single step. Figure adapted from Lockley and Hunt (1995). Images from: https://ucmp.berkeley.edu/science/trackways/trackways2.php 2.
Compare these two ichthyosaur fossils. What do you think differed between the environments in which they died? Explain the fossil evidence that led you to your answer. (4 pts) Fossil 1: https://3d.si.edu/enter-sea-dragon Fossil 2: https://skfb.ly/6U9MD The two ichthyosaurs probably lived in different ocean depths. The first fossil looks a lot skinnier and streamlined while the second seems fatter like it has more blubber/fat. The fat one probably lived in deeper waters since it would need more fat to hold in heat. The first one was also found with a lot of other ichthyosaurs so it could have been that it lived in a river with a fast current that ended up combining the ichthyosaurs bones together, while the second one was more isolated and complete so it
could have been at the bottom of the ocean. The scattering of the first ones bones could also mean it was scavenged and not the currents. 3.
Examine this fossil of Coelophysis
: https://skfb.ly/HuWQ
. Imagine how this dinosaur might have met its demise and become part of the fossil record. Based on the way the fossil was preserved, describe how you think the dinosaur died. Are there modes of death that you can rule out? What are two features of the environment that must have been true for this dinosaur to be preserved in this way? (4 pts) The dinosaurs could have died in some kind of mud incident. It looks like its head is up almost like it was trying to get air, and since the bones were so well intact and all together it most likely wasn
’
t above ground for very long. We could rule out dying by natural causes like age or starvation since that would have meant it was out in the open to the elements and would have been scavenged and much more damaged, the dinosaur also has food in its belly. After completing the lab assignment, take the quiz on Canvas. The quiz will ask you to report some of your answers from this lab and will provide you with feedback. You should feel free to correct any answers on your laboratory assignment you found were wrong after taking the quiz before submitting this assignment to Canvas. You may retake the quiz twice and you will receive your highest quiz score.
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help