USE THIS ONE PT 2_lab6 (1) (1)

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 Vertebra Caudal Region ~12 ~16 Neural arch/spine is connected to the top of the centrum. 23 Caudal Vertebra Caudal Region -- -- ^ 24 Caudal Vertebra Caudal Region -- -- ^ 25 Caudal Vertebra Caudal Region -- -- ^ 26 Caudal Vertebra Caudal Region -- -- ^ 27 Caudal Vertebra Caudal Region -- -- ^ 28 Caudal Vertebra Caudal Region -- -- ^ 29 Caudal Vertebra Caudal Region -- -- ^ 30 Caudal Vertebra Caudal Region -- -- ^ 31 Caudal Vertebra Caudal Region -- -- ^ 32 Caudal Vertebra Caudal Region -- -- ^ 33 Caudal Vertebra Caudal Region -- -- ^ 34* Caudal Vertebra Caudal Region ~10 ~10 ^ 35 Caudal Vertebra Caudal Region -- -- ^ 36 Caudal Vertebra Caudal Region -- -- ^ 37 Caudal Vertebra Caudal Region -- -- ^ 38 Caudal Vertebra Caudal Region -- -- ^ 39 Caudal Vertebra Caudal Region -- -- ^ 40 Caudal Vertebra Caudal Region -- -- ^

41* Caudal Vertebra Caudal Region ~10 ~4 Neural arch/spine is connected to the top of the centrum. Neural arch/spine begins to look thinner. 42 Caudal Vertebra Caudal Region -- -- ^ 43 Caudal Vertebra Caudal Region -- -- ^ 44 Caudal Vertebra Caudal Region -- -- ^ 45 Caudal Vertebra Caudal Region -- -- ^ 46 Caudal Vertebra Caudal Region -- -- ^ 47* Caudal Vertebra Caudal Region ~8 ~3 ^ 48* Tip of tail Caudal Region ~40 ~3 Located at the end of the caudal vertebrae. Longer than the rest of the centrum and without a neural arch. 49 Chevron Caudal Region -- -- Long and laying horizontally. 50* Chevron Caudal Region ^ 51 Chevron Caudal Region -- -- ^ 52 Chevron Caudal Region -- -- ^ 53 Chevron Caudal Region -- -- ^ 54 Chevron Caudal Region -- -- Long and laying vertically. 55 Chevron Caudal Region -- -- ^ 56 Chevron Caudal Region -- -- ^ 57 Chevron Caudal Region -- -- ^ 58 Chevron Caudal Region -- -- ^ 59 Chevron Caudal Region -- -- The chevron becomes stubbier and looks more triangular than the chevrons closer to the proximal of the organism. They are gradually becoming smaller in size. 60* Chevron Caudal Region ^ 61 Chevron Caudal Region -- -- ^ 62 Chevron Caudal Region -- -- ^ 63 Chevron Caudal Region -- -- ^ 63 Chevron Caudal Region -- -- ^ 65 Chevron Caudal Region -- -- ^ 66 Chevron Caudal Region -- -- ^ 67 Chevron Caudal Region -- -- ^ 68 Chevron Caudal Region -- -- ^ 69 Chevron Caudal Region -- -- ^ 70 Chevron Caudal Region -- -- ^ 71 Chevron Caudal Region -- -- ^ 72 Chevron Caudal Region -- -- ^ 73 Chevron Caudal Region -- -- ^ 74 Chevron Caudal Region -- -- ^ 75* Chevron Caudal Region ~1 ~1 ^ 2) Interpret the Skeleton (5 pts) a) What is the approximate total length of the tail? Be sure to use the scale bars in the images determine the length. (1 pt) The tail is about 350 centimeters long or 3.5 meters. That is relatively true if you were to use the 20 cm scale on the images provided.

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) In Assemblage A, it looks like there are gastroliths (if they are in the area the at had once occupied the digestive track) or gastromyths (if not found in the remains of the digestive track). If this definitely is a gastrolith then it is likely that that the bones present are parts of the ribcage and vertebrae. 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) I believe that the fossils in Assemblage A are not a part of the main specimen we are examining. I say this because of where Assemblage A is. So far, this dinosaur’s skeleton has remained well intact, there is not much disassembly – or the degree of disassembly needed to find the ribcage above the end of the tail. Moreover, the size of the bones associated with Assemblage A do not translate to the size of the bones in the main specimen. The ribcage present in Assemblage A looks to be similar in size to the smaller caudal vertebrae, the vertebrae found at the distal end of the tail, and the vertebrae found in Assemblage A look to be both smaller in size and different in shape than the main specimen. 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) There are several probable reasons that animals today swallow stones (or gastroliths) which can be translated to why a dinosaur would have consumed gastroliths. Some of these include: relieving hunger pains or to serve as a ballast (provides stability especially in water). However, the most likely reason for an organism to swallow a gastrolith was to aid in the grinding and crushing of foods. With this in mind, herbivores were the most likely group of dinosaurs to have gastroliths as they would consume tough plants that were difficult for the body to digest on their own. 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) The preservation of coprolites implies the environment they were preserved in was dry and arid. This is because decomposition of a coprolite was less likely in this type of environment.