Lab 7_Excavation Stage III (2)

DINOSAUR EXCAVATION STAGE III Part I: Excavation Stage III - Vertebral Column Below is “site map” image of the excavation site(s). These images, and others you will need to complete this assignment, are available at https://sites.google.com/tamu.edu/geol-207-dinosaur-world-ex-3/home . An arrow is labeled in the top right corner of your image indicating the direction of North. On your site map image, each bone has been numerically labeled. 1) Identify and Catalog the Bones use Table 3 on the next page to catalog the bones recovered during the excavation. For each numbered bone, you should identify the type of bone and the region of the body the bone is from (for this lab, appropriate regions are “cervical”, “dorsal”, “sacral”). Under notes, provide any features present that are important sharded derived characters that could help you in your identification. You should also provide an approximate measurement for each bone marked with a * using the scale bars on the zoom-in photos available at https://sites.google.com/tamu.edu/geol-207-dinosaur-world-ex3/home .

Table 3. Bone catalog for Excavation Stage 3. (5 pts) Bone Number Bone Identification Skeletal Region Measurements Other Notes Length (cm) Width (cm) 76* Sacrum Sacral 60 30 77* D13 Dorsal 30 10 78 D12 Dorsal -- -- 79 D11 Dorsal -- -- 80 D10 Dorsal -- -- 81 D9 Dorsal -- -- 82 D8 Dorsal -- -- 83 D7 Dorsal -- -- 84 D6 Dorsal -- -- 85 D5 Dorsal -- -- 86 D4 Dorsal -- -- 87 D3 Dorsal -- -- 88 D2 Dorsal -- -- 89* D1 Dorsal 20 7 90* C9 Cervical 15 7 91 C8 Cervical -- -- 92 C7 Cervical -- -- 93 C6 Cervical -- -- 94 C5 Cervical -- -- 95 C4 Cervical -- -- 96* C3 Cervical 14 6 97 Cervical -- -- 98 Cervical Ribs -- -- 99 Cervical Ribs -- -- 100 Cervical Ribs -- -- 101 Cervical Ribs -- -- 102 Dorsal Ribs -- -- 103 Dorsal Ribs -- -- 104 Dorsal Ribs -- -- 105 Dorsal Ribs -- --

4) Taphonomic considerations (3 pts) a) Bones #98-105 are ribs that articulate from the spinal column. How many ribs would you expect to be present if the skeleton was complete? How does the completeness of the ribs compare with the completeness of the spinal column? Provide a well-reasoned explanation for the differences you observe. (3 pts) If the spine was complete I would expect there to be 26 ribs. The difference is most likely because ribs are more fragile and prone to breakage as compated to the spinal column. Some ribs may have accidentally not been collected during the excavation on accident. 5) Use the Stratigraphic Column to Interpret the Age of the Dinosaur. (7 pts) Fossils can be used to create stratigraphic ranges that allow scientists to track the species duration, or longevity of groups, from their origination to their extinction in an area. The oldest fossil of a species is its first appearance datum (FAD) and the youngest fossil of a species is the last appearance datum (LAD). It may be helpful to think of FADs as the origination date of the group whereas you could think of LADs as the group’s extinction date . Examine the stratigraphic column on the next page before answering the questions below. The species below were found in this stratigraphic record. Using the information from their FADs and LADs (First Appearance Datum and Last Appearance Datum, respectively) to constrain the age of the excavation site, denoted as a bone icon on the stratigraphic chart. Organism FAD Age (Ma) LAD Age (Ma) Aquilapollenites 81 65 Baculites asperformis 80 75 Crassostrea subtrigonalis 77 66 Wodehouseia spinata 69 66 Momopites 66 62 Caryapollenites 62 57 1. What is the potential age range, in millions on years (Ma) of the excavation site? (1 pt) The potential age range could be from 77 million years ago to 69 million years ago. 2. What geologic age is excavation site? List the Geologic Period and Geologic Age after consulting the international stratigraphic chart. (1 pt) This is the Cenozoic Era, specifically the Paleogene Period and within the Paleocene Epoch.

Knowing the age of the excavation site should help you constrain the identity of the dinosaur. 3. Describe the changes in the environment of deposition starting from the oldest interval. For each stratigraphic interval, make a claim about the type of environment, state your evidence, and explain your reasoning. Be as specific as your evidence will allow. (5 pts) a. Lowermost stratigraphic interval (Oldest interval) This is a marine environment, my evidence being the presence of Aquilapollenites and Crassostrea subtrigonalis. Aquilapollenites is an extinct pollen grain genus and Crassostrea subtrigonalis is an oyster species which both indicate a marine environment. b. Dinosaur-bearing Interval The environment is terrestrial, with dinosaur fossil/remains suggesting a mixed habitat consisting of marshes, grasslands, and forests, where dinosaurs once roamed, shown by the "Dinosaur-bearing Interval" concept, although specific details are not provided. c. Uppermost stratigraphic interval (Youngest interval) The environment is terrestrial as seen by the presence of Wodehouseia spinata and Caryapollenites, which are pollen grains from marine sediments moving to terrestrial habitats, and the fossil plant species Wodehouseia spinata, suggesting a shift from marine to terrestrial ecosystems.