生物代写|Paleontology Lab Report – GLY3105

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Lab 5 GLY3105C

Introduction to Paleontology

Goal: To be able to identify different kinds of fossils and how they preserve, determine the kind of symmetry present in those fossils, and understand the taxonomic classification given to fossils. All fossils displayed in this document are either from personal collection, The Florida Museum of Natural History, or under usage via public domain.

Note. All answers should be in your own words. If you wish to use secondary sources, you may do so, but please cite them (APA format) in the “Works Cited” section at the bottom of the assignment. Do not use Wikipedia for anything but as a launchpad to find other sources. It is an excellent for finding true sources, but not a 100% good source in itself. For APA citation regulations please click on the hyperlink. An example is given for you already in the “Works Cited” section.

Part 1 What Is a Fossil and How Do Living Things Become Fossils?

The term “fossil” is used by scientists to distinguish the remains, impressions, or traces of living organisms that are (1) at least 10,000 years old (debatable), (2) are not human (Homo sapien) in nature (including human remains and artifacts such as pottery, spearheads, etc.), and (3) are geologically altered in some way. Paleontology is differentiated from archaeology or anthropology in the fact that it does not deal with humans (defined as our species H. sapien) and instead focuses on all other forms of life that have once lived on our planet.

The most well-known kind of fossil is your typical “body” fossil. These kinds of fossils are the hard parts (wood, shells, exoskeletons, horns, bones, etc.) of some organisms that are preserved after being buried post-mortem. Taphonomy is the study of this fossilization process. Being buried helps protect these remains from scavengers and chemical processes that would degrade them on the surface. Underground metamorphic processes and other geologic activities can destroy these remains as well, however. Some geologic processes can actually assist to make these remains tougher and harder to destroy. These taphonomic processes include:

1. Permineralization – the filling in of pores and spaces present in the remains with new minerals and chemical compounds. Common fillings include calcite, pyrite, carbonate, and silica, although there are others. This process increases the density and strength of the remains, and drastically increases chances of preservation.

• Replacement – the original mineral composition of the remains is degraded and replaced with new materials at such a fine scale that the original details of the remains stay intact. The mineral composition can vary slightly or be completely different from the original. Common replacements include dolomite, pyrite, calcite, iron oxides, and silica.

• Recrystallization – the original mineral and chemical composition is changed, similar to replacement, but without as fine of detail due to the remains being converted to coarse crystals. These crystals are typically able to be seen by the naked eye.

Sometimes, fossils preserve exceptionally well to a point where they are mostly unaltered by geologic processes. These unaltered kinds of fossils are relatively rare and can preserve hard parts, soft parts, or both.

• Mummification – A process that involves the desiccation of soft tissue due to an incredibly dry environment. Similar to the process of intentional human mummification in past civilizations. These preserve soft tissue in incredible detail and are almost always less than a few million years old.

• Freezing – Relatively self-explanatory (I hope). A process that involves an animal being frozen at the time of or shortly after death. These fossils are found in very cold environments such as the permafrost from Siberia and Alaska. Similar to mummification, these soft tissues are incredibly well preserved but are almost always less than a few million years old (more typically less than a million).

• Amber Preservation – A process that involves the preservation of small organisms or parts of organisms in hardened tree resin (amber). Body fluids ingested by these small organisms are not preserved (sorry, not sorry pop-culture fans).

• Hydrocarbon Preservation – A process that involves the preservation of hard remains in liquid tar or asphalt (La Brea Tar Pits). These preservation conditions prevent weathering of hard materials (bones, horns) via chemical and physical processes. The chemical composition of these hard remains are thus unchanged from the original. Soft tissues are often not preserved, however, for they decay due to bacteria still having access to the remains.

• Unaltered Preservation – Some hard parts are made out of naturally very tough material and thus preserve well naturally. Teeth and relatively young shell fossils are typically considered unaltered due to their stable mineral composition. This is why shark teeth are one of the most common finds among vertebrate fossils. 

Fossils may not always preserve the original remains but may be molds or casts of the original. These kinds of fossils are formed through processes such as:

• Carbonization – A process that involves the dissolution of the remains after being pressed into the sediment. Degradation of the remains due to heat, pressure, and chemical processes leave behind a thin carbon film of the original remains. This is the most typical way in which soft organisms are preserved (leaves, jellyfish, worms, feathers, fleshy parts of fish and other animals, etc.).

1. External Molding – A process that involves the pressing of remains into sediment that then solidifies into rock. This leaves behind an impression in which the external details of the original remains can be identified, even though the original remains are not necessarily preserved. The original remains can be preserved separately but are not preserved due to the formation of the impression (think about a seashell being pushed in clay, the clay will preserve the details of the shell through the impression but will not necessarily preserve the shell itself).

1. Internal Molding – A process that involves the filling of cavities in the original remains of organisms with sediment. This sediment can harden and form a mold of the inside of the remains (typically a shell). These molds will often preserve internal details of past organisms and are very useful to paleontologists. An internal mold of clams and other bivalves are relatively common due to the large cavities they contain in their shells.

1. Casting – A process that involves the filling in of an external mold with sediment that then hardens. Similar to internal molds, but forms in the impression of the remains instead of within the remains themselves. Think of pressing a shell into some clay, letting the clay harden, and then filling the impression with another substance (similar to a cupcake sheet). This filling of the impression would be a cast. Casts will usually not preserve as much detail as an internal mold (making an impression of an impression usually does not preserve much other than the general shape).

Some fossils are not related to the actual remains of organisms at all, but instead simply indicate their existence. These fossils are still incredibly important to science, however, and should not be discounted. Other types of fossils aside from body fossils are:

1. Ichnofossils – preserved tracks, tail drags, trails, body impressions, and burrows of animals that once existed. These often form in sediment layers that are preserved relatively quickly after an animal has left an impression in them. Can sometimes be used to determine how an animal moved, and/or how fast they moved. Some ichnofossils could even indicate swimming in normally terrestrial animals.

• Coprolites – preserved waste of animals, usually in the form of feces. These can be preserved in ways similar to body fossils, but especially in cast and mold forms. Usually are identified based on a dung like shape or evidence of digestive material. These kinds of fossils were used to determine that grass appeared in the very late Cretaceous Period (~66 million years ago)

• Gastroliths – preserved gizzard stones of ancient reptiles and birds that were once used to help grind food. Usually are identified by being exceptionally round stones near remains and other areas they should not be. Based on this, we know that some dinosaurs actually used gastroliths like extant avian dinosaurs (birds) today.

• Chemical Fossils – recent technology has allowed scientists to detect chemical residue that is organic in nature and is indicative of a now absent animal or plant. Only real information received is the presence of an organism within the paleoenvironment.

• Psuedofossils – sometimes minerals and rocks form in ways that seem very similar to fossils but are not. These are referred to as psuedofossils and are often either concretions that form due to mineral precipitation in sediment or rocks that have been eroded to somewhat look organic in nature.

• Subfossils – remains of organisms that do not fit the criteria to be considered a fossil (usually too young).

Table 1: Fossil Types and Preservation Process

Specimen	Taxonomy	Fossil Type	Preservation Process (Body Fossils)	Image Credit + Specimen Location
	Aves (No further given classification)	Ichnofossil(Footprints)	N/A	Image Taken by Luis Torres (TA) + Specimen on Display at the Florida Museum of Natural History
	Mercenaria sp. Quahog (Venus Clam)	Body Fossil	Permineralization Replacement	Image Taken by Luis Torres (TA) + Specimen Within Personal Collection
	N/A Septarian Concretion (See note below)	Psuedofossil	N/A	Image Obtained from Wikimedia under Public Domain + Image Released by Mark A. Wilson
	Laevitrigonia gibbose Trigonid Clam	Internal Mold	N/A	Image Obtained from Wikimedia under Public Domain + Image Released by Mark A. Wilson
	Unspecified sp. Cnidarian	External Mold (Top) Cast (Bottom)	N/A	Image Taken by Luis Torres (TA) + Specimen on Display at the Florida Museum of Natural History
	Unspecified sp. Chiroptera(Bat)	Carbonization	N/A	Image Taken by Luis Torres (TA) + Specimen on Display at the Florida Museum of Natural History

• *Note. A septarian concretion is a carbonate rich concretion that typically forms from mud deposits that become dehydrated, resulting in that turtle shell like cracking. This is not the remains of a past organism, and thus is not a fossil.

Part 2 Symmetry in Fossils

Identifying the symmetries found in different fossils are useful in identifying the organism that formed them. Symmetry itself is defined as a pattern seen in shapes in which two halves across an axis show similar size, shape, and structures. There are three main types of symmetry listed as the following:

1. Bilateral Symmetry – Symmetry that is shown primarily on a single axis that has traveled through a central point. This kind of symmetry is seen in most organisms such as vertebrates, arthropods, and some other invertebrates.

• Radial Symmetry – Symmetry that is shown on multiple axes that travel through a central point. Usually refers to bilateral (2 axes), pentamerous (5 axes) and hexamerous (6 axes) symmetry. This kind of symmetry is usually seen in invertebrates such as echinoderms (starfish, sand dollars) and cnidarians (jellyfish, hydras, anemones).

• Spherical Symmetry – Symmetry that is shown on all axes as long as they travel through a central point. Usually seen in microscopic forms of life, such as bacteria and foraminifera.

• Asymmetry – Not a form of symmetry, in fact, it is a complete lack of symmetry. Usually in reference to a certain plane. Sponges are typically asymmetric.

Table 2. Typical Symmetries

Bilateral Symmetry	Radial Symmetry	Spherical Symmetry	Asymmetry
Image Taken & Edited by Luis Torres (TA) + Specimen Within Personal Collection	Image Obtained from Wikimedia under Public Domain, Edited by Luis Torres (TA) + From the Biodiversity Heritage Library	Image Taken & Edited by Luis Torres (TA) + Specimen on Display at the Florida Museum of Natural History	Image Obtained from Wikimedia under Public Domain, Edited by Luis Torres (TA) + From the Biodiversity Heritage Library

Planes of Symmetry:

When referencing what kind of symmetry an organism has, a reference is usually made to some sort of “plane”. A plane is an axis in space that divides an object or organism. Something that is referenced as having bilateral symmetry is typically referring to having symmetry along the sagittal plane. Organisms with radial symmetry or spherical symmetry typically have symmetry among a few or more planes. See Figure 1 for a couple of examples of different planes.

Figure 1. Major Planes of Symmetry

Note. Image Obtained from Wikimedia under Public Domain + Image Released by the National Cancer Institute.

Part 3 Taxonomy: Classifying the Natural World Past & Present

Humans appreciate when things are put into boxes that classify them based off a number of criteria. Organisms are often classified based on DNA in which genetic material can be obtained or based on morphology and evolutionary relationships when it cannot. Due to the fact that the oldest usable DNA found is only one million years old, morphology is the most common way of classifying extinct organisms. In this classification process, a naming system was developed so biological specimens both fossil and otherwise can be easily referenced. This is what is called “Taxonomy”. You may have previously read some taxonomic classifications within this paper. The term “echinoderms” refers to the taxonomic group of “Echinodermata” in which the organisms known as starfish, sea urchins, sand dollars, and other relatives reside.

These classifications start out very broad (including many different organisms) and get progressively more specific moving down the taxonomic chain, with the most specific being genus and species. Typically, when referring to a single species, the genus and the species name is referenced. If referring to the human taxonomic species, it would be referred to as “Homo sapien” with “Homo” being the genus and “sapien” being the species (when writing genus and species, it is proper to italicize them, but not other broader classifications). Taxonomic names are typically in a non-romantic language, such as Latin, Greek, or even native languages where the first fossil of the organism was found. The human species name Homo sapien is Latin for “wise man”, with Homo meaning “human” and sapien meaning “wise”.

Taxonomy is very important for paleontology, for without it there would be significant difficulty in referring to certain specimens as belonging to a certain group of extinct organisms. Even the name of the blockbuster movie star Tyrannosaurus rex (Tyrant-lizard king) would be difficult to learn about if we did not classify specimens that we believe belong to this species, as being so.

Sometimes, classifying species down to a species level is difficult if not impossible. For example, if a specimen is able to be named down to a genus level but not a species level, then in front of the genera the term species would be used instead. This is seen in the “Quahog Venus Clam” taxonomic classification in Table 1. The genus is named as Mercenaria, but species (sp.) is used to signal that it has not been, or is unable to be, classified down to a species level. See Table 3 for the different taxonomic classifications.  

Table 3 Taxonomy of Different Organisms

This taxonomic classification is not a perfect system, however. Further sub-classifications have had to be formed to recognize different subgroups (I am not going to have you memorize them, that’s just cruel, especially for plants). A taxonomic grouping that includes a common ancestor and all of its descendants is simply called a “clade”, so most of these classifications could be referred to as such (Example. The class “Mammalia” can be referred to as the “Mammalia clade” or “Mammalian clade”). Due to difficulty of assigning a species to an ichnofossils, they often receive unique classifications.

It should be noted that sometimes taxonomic classifications change based on new information. This is especially true in paleontology, due to the fact that most of the classifications are morphology based. As new information is gathered from freshly discovered specimens and innovative techniques, the idea of where a particular organism belongs on the tree of life can shift. An example can be seen with the dire wolf, an extinct animal that was morphologically classified as sharing the genus Canis with grey wolves (Canis lupus). Recent genomic evidence (DNA) put forward in a scientific paper by Perri et al (2021) suggests, however, that the dire wolf was actually not a wolf at all but was actually a much closer relative to African jackals. Due to this, the genus and species were changed from Canis dirus to Aenocyon dirus. This is unusual for extinct animals, however, and usually a shift of taxonomic classification is based on learning more about the morphology or evolutionary relationships between different organisms.

Part 1 Questions:

1. (a) What is Taphonomy? (b) Why is taphonomy important in relation to paleontology?

• Which fossilization process has the highest chance of preserving soft tissues?

• Why are shark teeth among the most common finds in regard to vertebrate fossils?

•  Can extinct animals be brought back via DNA preserved in amber? Why or why not?

Part 1 Activity:

Instructions: Using the Part 1 reading and Table 1, fill in the missing sections of Activity 1 Table below. (10 points)

Specimen	Taxonomy	Fossil Type	Preservation Process (Body Fossils)	Image Credit + Specimen Location
	N/A Rock Covered in Iron Oxide	Psuedofossil	N/A	Image Taken & Edited by Luis Torres (TA) + Specimen Within Personal Collection
	Mesolimulus sp.		N/A	Image Taken by Luis Torres (TA) + Specimen on Display at the Florida Museum of Natural History
	Clypeaster sp.		Replacement &Permineralization	Image Taken & Edited by Luis Torres (TA) + Specimen Within Personal Collection
	Lepidodendron sp. Scale-Tree	Body Fossil		Image Obtained from Wikimedia under Public Domain, Edited by Luis Torres (TA) + From the Biodiversity Heritage Library
	Eupatagus antillarum	Body Fossil		Image Taken & Edited by Luis Torres (TA) + Specimen Within Personal Collection
	Alethopteris sp.		N/A	Image Taken by Luis Torres (TA) + Specimen on Display at the Florida Museum of Natural History
	Falsilyria sp.	External Mold (Right) &________(Left)	N/A	Image Taken by Luis Torres (TA) + Specimen on Display at the Florida Museum of Natural History

Part 2 Questions:

1. (a) Along what plane do humans have bilateral symmetry? (b) What other organism has bilateral symmetry among the same plane?

• (a) What kinds of organisms typically have bilateral symmetry? (b) Radial Symmetry? (c) Spherical Symmetry?

Part 3 Questions:

1. List the taxonomic designation of an American Beautyberry (domain through species)

• List the taxonomic designation for any bacteria species (domain through species).

• List the taxonomic designation for any archaea species (domain through species).

• What are two different reasons why the taxonomic classification would change in an organism or group of organisms?

• List the taxonomic designation of the dire wolf both prior and after it’s classification shift from Canis dirus to Aenocyon dirus (domain through species).

Part 4 Activity Museum Visit: Visit a museum either in-person or virtually (see links below). Take pictures of 5 fossils and elucidate their (a) method of preservation (only if the fossil is a body fossil), (b) symmetry, and their (c) Full taxonomy (from Kingdom down to Species or the lowest level available). Remember that Ichnofossils typically receive a unique classification. (20 points)

Virtual Museum Links:

http://www.fossilmuseum.net/

Works Cited:

Perri, A. R., Mitchell, K. J., Mouton, A., Álvarez-Carretero, S., Hulme-Beaman, A., Haile, J., Jamieson, A., Meachen, J., Lin, A. T., Schubert, B. W., Ameen, C., Antipina, E. E., Bover, P., Brace, S., Carmagnini, A., Carøe, C., Samaniego Castruita, J. A., Chatters, J. C., Dobney, K., … Frantz, L. A. (2021). Dire wolves were the last of an ancient New World Canid lineage. Nature, 591(7848), 87–91. https://doi.org/10.1038/s41586-020-03082-x

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