Lab5_Excavation Stage I (1)

DINOSAUR EXCAVATION STAGE I Part I: Excavation Stage I - Pelvic Girdle and Hindlimb A new fossil site has just been excavated and you are on the team that must identify what has been found. In the next 4 laboratory assignments you will examine different portions of the skeleton and use anatomical clues to narrow down the possible identity the fossil. After completing all 4 assignments, you will be placed in groups to compare your evidence and create a consensus report on your findings. 1) Find Your Bearings. 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-ex1/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.

2) Identify and Catalog the Bones: use the Table 1 below 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, “hindlimb” and “pelvis” are appropriate terms for skeletal region). 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-ex1/home . Table I. Bone catalog for Excavation Stage I. (5 pts) Bone Number Bone Identification Skeletal Region Measurements Other Notes Length (cm) Width (cm) 1* Femur Hindlimb 80 20 Biggest bone of the three 2* Tibia Hindlimb 70 10 3 Fibula Hindlimb -- -- 4* Tarsometataur sus Hindlimb 50 10 5 Dewclaw Hindlimb -- -- 6 Phalange Hindlimb -- -- 7 Phalange Hindlimb -- -- 8 Phalange Hindlimb -- -- 9 Phalange Hindlimb -- -- 10 Ungual Hindlimb -- -- 11 Phalange Hindlimb -- -- 12 Phalange Hindlimb -- -- 13 Phalange Hindlimb -- -- 15 Phalange Hindlimb -- -- 16 Phalange Hindlimb -- -- 17 Ungual Hindlimb -- -- 18 Pubis Pelvic -- -- 19 Ischium Pelvic -- -- 20 Illium Pelvic -- -- 21 Astragalus Hindlimb -- -- 22 calcaneum Hindlimb -- --

f) How many functional digits are there on the foot? (1pt) Four 4) Evaluate your evidence to reach a preliminary identification (10pts) Below is a phylogeny depicting the major groups of dinosaurs. The letters depict possible positions of shared derived characters on the phylogeny. Describe where the shared derived characters you came across when examining the pelvis and hindlimbs would fall on the phylogeny using the letters. [You should have at least 4 characters to place from #3.] (4 pts) We have F, A, G, B because of the pubis being posterior oriented, specialized ankle joint, phalange formula, and four digits. Given the evidence you have so far, what clade of dinosaur do you have? State your claim (the clade), list your evidence, and explain your reasoning. (6 pts) The clade of dinosaur we have is sauropoda. This is because of the orientation of the pelvis and phalange formula. The formula is similar to the specimen presented as well.

5) Interpreting the Depositional Environment (8 pts) Sedimentary structures are geologic features of the substrate that were preserved and provide evidence for the environment of deposition ( e.g., streams, deserts, etc). Use supplementary table 1 to answer the following questions: 1. A few sedimentary structures discovered at the dig site are mud-cracks , ripple marks , and trackways. In what type of environment would we expect to see each of these sedimentary structures? (3 pts) a. Mudcracks: hot desert climates b. Ripple Marks: climate with large body of water c. Trackways: flat and dry climates 2. Many different types of rocks are found within this field site, including siltstones, limestones, and evaporites. Given this evidence, make a claim about the depositional environment and provide your reasoning. (1 pt) The hints suggest that this was once a large body of water climate. A lot of these rocks were found in a water environment which is supported by the rocks found. 3. Some fossils can be used as an indicator of the depositional environment. Within the field site, you find a few fish fossils similar to the fish bones found at the Green River Formation. Given this evidence, make a claim about depositional environment and provide your reasoning. ( 1 pt) Fish bones further suggest that the environment is some kind of water climate, or once was. These are like a river formation which would suggest that this is a lake or river. 4. Given all the geological evidence in #1-3, make a claim about the most likely depositional environment and provide a well-reasoned argument. ( 3 pts) Because of the evidence given, I think that the environment is a dried-up lake or river. This is because there is sedimentary evidence to suggest this like mud, sand, and ripples. The types of rocks found also are those commonly found in large bodies of water. There was also evidence of fish bones with are similar to those found in a river.