Lab6_Excavation Stage II

Dinosaur Excavation Stage II Part I: Excavation Stage II – Caudal Region 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- ex2/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 2 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 (in this lab, all bones are from the caudal 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-ex2/home Table 2. Bone catalog for Excavation Stage II. (10 pts) Bone Number Bone Identification Skeletal Region Measurements Other Notes Length (cm) Width (cm) 22* Caudal vertebrae Caudal ~8-10 ~16-18 23 Caudal vertebrae Caudal -- -- 24 Caudal vertebrae Caudal -- -- 25 Caudal vertebrae Caudal -- -- 26 Caudal vertebrae Caudal -- -- 27 Caudal vertebrae Caudal -- -- 28 Caudal vertebrae caudal -- -- 29 Caudal vertebrae Caudal -- -- 30 Caudal vertebrae Caudal -- -- 31 Caudal vertebrae Caudal -- -- 32 Caudal vertebrae Caudal -- -- 33 Caudal vertebrae Caudal -- -- 34* Caudal vertebrae caudal ~8 ~8 35 Caudal vertebrae Caudal -- -- 36 Caudal vertebrae Caudal -- --

37 Caudal vertebrae Caudal -- -- 38 Caudal vertebrae Caudal -- -- 39 Caudal vertebrae Caudal -- -- 40 Caudal vertebrae Caudal -- -- 41* Caudal vertebrae caudal ~8 ~4 42 Caudal vertebrae Caudal -- -- 43 Caudal vertebrae Caudal -- -- 44 Caudal vertebrae Caudal -- -- 45 Caudal vertebrae Caudal -- -- 46 Caudal vertebrae Caudal -- -- 47* Caudal vertebrae Caudal ~10 ~4 48* Caudal vertebrae/ Chevrons Caudal ~43 ~4 49 Chevrons Caudal -- -- 50* Chevrons caudal ~8-10 ~2 51 Chevrons Caudal -- -- 52 Chevrons Caudal -- -- 53 Chevrons Caudal -- -- 54 Chevrons Caudal -- -- 55 Chevrons Caudal -- -- 56 Chevrons Caudal -- -- 57 Chevrons Caudal -- -- 58 Chevrons Caudal -- -- 59 Chevrons Caudal -- -- 60* Chevrons Caudal ~6 ~3-4 61 Chevrons Caudal -- -- 62 Chevrons Caudal -- -- 63 Chevrons Caudal -- -- 63 Chevrons Caudal -- -- 65 Chevrons Caudal -- -- 66 Chevrons Caudal -- -- 67 Chevrons Caudal -- -- 68 Chevrons Caudal -- -- 69 Chevrons Caudal -- -- 70 Chevrons Caudal -- -- 71 Chevrons Caudal -- -- 72 Chevrons caudal -- -- 73 Chevrons Caudal -- -- 74 Chevrons Caudal -- -- 75* Chevrons Caudal ~2 ~3.5 2) Interpret the Skeleton (5 pts)

- Well, it’s between sauropods and theropods due to the last lab however I’m inclined to think that it’s a theropod due to its smaller stature. However it could be a juvenile sauropod, but due to the condition of the pelvic girdle and leg structure I still think that it’s a theropod. b) Are there any dinosaur groups that your evidence can rule out? State you claim (“This could not be the Clade X…”), list your evidence, and explain your reasoning. (5 pts) - It’s not the ornithischian clade as they have a completely different type of pelvic girdle and generally have a different type of caudal vertebrae set up being more compact than those of saurischian dinosaurs.

4) Interpret the Paleoecology and Environment (5 pts) To place a fossil skeleton in the a paleoecological and environmental context, we often look for the nearby remains of other organisms as well as biogenic sedimentary structures are called trace fossils . Trace fossils, or ichnofossils , are traces of living organisms ( such as burrows, trackways, root marks, etc .) that have been preserved in the substrate and provide evidence for the organism’s behaviors. Certain trace fossils can only be preserved in a specific type of depositional environment, thus they can also be used in paleoenvironmental interpretation. There are two sets of trace fossils were preserved near the caudal region of this skeleton. a. Examine Assemblage A on the dorsal side of the caudal region. What type of fossils are presented in this assemblage? (1 pt) - It looks like the remains of another dinosaur and some gastroliths. b. Do you think the fossils in Assemblage A are part of the same individual as the main skeleton? Make your claim, describe your evidence, and explain your reasoning. (2 pts) - There could be a chance that it is, however, I don’t think it is because the way the tail is laid out compared to Assemblage A wouldn’t make sense and the length of the tail wouldn’t be supported by what I would assume to be the ‘body’ of assemblage A. c. The small rounded stones in Assemblage A are gastroliths. What is the function of gastroliths to an organism? Which groups of dinosaurs would you expect to have gastroliths? (1 pt) - Gastroliths are mainly used to help break down eaten plant matter and I would expect herbivore dinosaur/ornithopod. d. Assemblage B near the distal end of the caudal region contains coprolites. What does the preservation of coprolites imply about the environment in which these fossils were preserved? (1 pt) - That it was surrounded by phosphatic minerals and other mineralizing material and very arid.