Lab5_Excavation Stage I_CharleeWessels

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 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 85*cm 10-20* cm The main bone in the group 2* Tibia Hindlimb 70*cm 10*cm Paired with 3 (lower part is 22) 3 Fibula Hindlimb 65*cm 10-3*cm Paired with 2 (lower part is 21) 4* Tarsometatar sus Hindlimb 50*cm 15* cm Akle like 5 Ungual Hindlimb 2* cm 5* cm Dew claw-like 6 Phalanges Hindlimb 8* cm 3*cm Top First knuckle 7 Phalanges Himdlimb 7*cm 2*cm Top Second knuckle 8 Phalanges Hindlimb 6*cm 2*cm Top Third knuckle 9 Phalanges Hindlimb 3*cm 2*cm Top Fourth knuckle 10 Ungual Hindlimb 5*cm 1*cm Top Talon 11 Phalanges Hindlimb 13*cm 5*cm Middle First knuckle 12 Phalanges Hindlimb 7*cm 4*cm Middle Second knuckle

what we are shown, it seems that all the bones are still part of the specimen. c) Bones 21 and 22 of our organism represent the ankle bones. What type of ankle configuration does our organism have? (Appropriate terms could be “ crurotarsal ankle” like in the left figure or “ mesotarsal ankle” like in the right figure. The red line in each is the plane of the ankle hinge). (1 pt) - The organism has a crurotaral ankle. The Astragalus and Calcaneum are uneven just like the left diagram. The right diagram has the two even showing that this organism most likely does not have a metatarsal akle. d) What features are present in this portion of the skeleton that make you confident this fossil is a dinosaur? Consider the shared derived characters that are unique to Dinosauria and are not present in other groups. (1 pt) - The hole in the hip was a good indicator that this was a dinosaur. The pelvic area can tell us a lot about the specimen, and it has a lot of telling characteristics to support that is a dinosaur. One of these telling characteristics is the hind limbs directly below the body. The hind legs do seem to fit into the category. e) Examine the hip and the orientation of the pubis. What type of hip is present in this specimen? (1pt) - This pubis is t-shaped and is facing the opposite direction of the ischium. This means that this specimen most likely has a saurischian pelvis. f) How many functional digits are there on the foot? (1pt) - There are three functional digits on this specimen’s hind leg.

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) - By looking at this phylogeny, I think that this specimen has to be somewhere under the F. It seems that the pelvic bone changes are between F and C. I know that the dinosaurs under F have similar pelvic structures as the specimen, so that is my first direction. Next, I know that the hindlegs have some sort of talons and that there are similar dinosaurs under both G and H, but H seems to be more closely related.

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 hypothesize that the depositional environment was a water source and dried up and became some sort of muddy environment, which helped conceal all of the specimens. The presence of siltstone and fish helps support the hypothesis.