MiniAssignment1_BoneDectectivesWorksheet

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Texas A&M University *

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207

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Anthropology

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Apr 3, 2024

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Bone Detectives Worksheet This mini-assignment goes with the lecture segment titled “Bone Detectives.” Please use this worksheet while viewing the lecture segment. It will require information from the video to complete. Evidence collected from the Cleveland Lloyd Dinosaur Quarry: What organisms are preserved? • The majority of the individuals preserved are from a single species of carnivore, Allosaurus. • As evinced by the size distribution of the Allosaurus leg bones, most of the Allosaurus specimens are sub-adults rather than fully grown adults. • The other species are not as common but appear to be adult specimens rather than juveniles. What bones are preserved and what are their biological characteristics? • The bones occur throughout the mudstone. Larger bones are at the top and bottom of the deposit, and smaller bones are concentrated in the middle to upper layer. • The smallest bones like wrist/ankle bones (carpals/tarsals), finger/toe bones (phalanges), hand and foot long bones (metatarsals/metapodials) bones from the underside of the tail (chevrons) are under-represented. • The bones of different individuals are mixed together. What are the taphonomic characteristics of the bones themselves? • Looking closely at the bones, they are very well preserved and show very little weathering. The degree of weathering is consistent with being exposed at the surface for no more than 2 years. • 30% of the bones have fractures • Bones that are fractured tend to be more abraded and their edges are more rounded than they would have been in life. But the abrasion in relatively minor. • 4% of the bones have tooth marks • The deposit is a fossiliferous mudstone with an overlying limestone. • The bones are almost always preserved horizontally. • There is no preferred compass orientation of the bones. • There is a lot of small bone particles preserved throughout the mud.

1. Use the evidence above to consider the hypothesis that the animals were preserved because they became mired in mud. 1a. Which claim do you think the evidence supports? I think the evidence supports claim 2. Claim 1: This deposit represents a collection of animals that became mired in mud. Claim 2: This deposit DOES NOT represent a collection of animals that became mired in mud. 1b. What evidence above supports the claim you chose? The evidence above that supports the claim I chose is that the bones of different individuals are mixed together, the smallest bones are underrepresented, and the placement of the larger bones towards the top and bottom, while the smaller bones are concentrated in the middle to upper level. 1c. Explain the reasons you think the evidence supports the claim you chose? The reasons why I think the evidence supports the claim I chose is because it implies that the individuals were not all together in one solid structure or piece. The mud would have preserved the bones of everyone and as stated in the evidence above, the smallest bones were underrepresented. The mud also would have encased the individuals in a life position, and we see that larger bones were positioned towards the top and bottom, while smaller bones were concentrated in the middle to upper layer, so the individuals were not in life position. The lecture also states that even if the mud was acidic small bones would be preserved, but we are missing smaller bones. 2. After considering all the claims the discussed in the video , state the claim you think is best supported . You may also choose a claim that was not discussed in the video or combine claims if you like (Ex. A population died catastrophically but was then transported to the site after death.) I think the claim that was best supported was a depositional basin that had bones transported to it. 3. List the evidence that supports the claim you stated in #2 and explain your reasoning in a few sentences. The evidence that supports the claim I stated in question two is that the smallest bones were underrepresented. As discussed in lecture, small animals and small bones of larger animals may not be preserved if those were transported far away. This could explain the missing smallest bones of the larger animals. Another thing was that 30% of the bones had fractures. This could be due to the bones being trampled on as other animals walk through the lakebed. Lastly the bones of different individuals were mixed together. This could be explained by the fact that during the transportation bones were mixed up and therefore would be separated from one another.

4. State a claim discussed in the video that you think is ruled out by the evidence. What is the least likely scenario that could explain this fossil deposit? Describe the evidence supports your assertion and explain your reasoning. I think a claim discussed in the video that is ruled out by the evidence is the dried-up pond. I think the dried-up pond is ruled out by evidence because there were multiple different populations of individuals present at the pond and not just one single population. Another piece of evidence that discredits this claim is that the bones were well preserved and showed very little weathering. Due to the pond drying out we would expect the bones to be exposed to weathering processes. Another thing is that the bones from individuals were all mixed together. If the pond dried up, bones from the individual would be associated with each other and this was not the case.

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MiniAssignment1_BoneDectectivesWorksheet

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