Lab5_Excavation Stage I

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 Hind limb 80 15 2* Tibia Hind limb 70 10 Larger than fibula 3 Fibula Hind limb -- -- 4* Tarsometatars us Hind limb 54 15 5 Ungual Hind limb -- -- Looks like a claw 6 metatarsal Hind limb -- -- Bigger than phalanges 7 Phalange Hind limb -- -- Seem to be part of foot 8 Phalange Hind limb -- -- Seem to be part of foot 9 Phalange Hind limb -- -- Seem to be part of foot 10 Ungual Hind limb -- -- Looks like a claw 11 Metatarsal Hind limb -- -- 12 Phalange Hind limb -- -- Seem to be part of foot 13 Phalange Hind limb -- -- Seem to be part of foot 15 metatarsal Hind limb -- -- 16 Phalange Hind limb -- -- 17 ungual Hind limb -- -- 18 Illium Pelvis -- -- Had a large ball joint socket 19 ischium pelvis -- -- 20 Pubis pelvis -- -- 21 Hind limb -- -- 22 Hind limb -- --

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) 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) I believe the animal that these bones belonged to is the ornithodrians because of the fact that it has three digits instead of more like 5 or so. Secondly, the mesotarsal ankle is a character that characterizes this group. Additionally, the dinosaur had unguals which are very useful for bird like animals. Finally, the animal couldn’t be specifically identified as a dinosaur, so it can fit on that part of the phylogeny being before dinosaurs.

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: once saturated with water b. Ripple Marks: previously had shallow water c. Trackways: previously streams/rivers 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) Shallow calm waters where there was previously a river/stream leading to a delta because the sedimentary structures determine it is shallow water 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) This confirms my theory that it is a delta because the green river has a delta. 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) I believe that it is a where there was once a delta because all of the sedimentary structures and rocks found point to the site having calm shallow water, which suggests a river/stream.