MiniAssignment5_COMPLETE (2)

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Texas A&M University *

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Medicine

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Apr 3, 2024

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docx

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Uploaded by MajorBeaver4076

Major groups of dinosaurs and the hip mini-assignment For details on the hip, read pages 51-55 and 343 of your textbook (Dinosaurs by Lucas). 1. One important dinosaurian synapomorphy is the perforate (pierced or open) acetabulum , simply a "hip bone" (actually three connected bones, together called the pelvis) with a hole in the center where the head of the femur ("thigh bone") fits. What are the three bones that comprise the pelvic girdle ( e.g., “hip bone”)? (2 pts) i. “Ilium” ii. “Ischium” iii .“Pubis” iv. “Acetabulum”    2. Dinosauria contains two major groups of dinosaurs: the Ornithischia , or "bird-hipped,” and the Saurischia , or "lizard-hipped," dinosaurs. The most prominent difference between the two types of hip is the orientation of the pubis. For each group, indicate whether the direction (anterior or posterior) the pubis generally projects from the pelvic girdle. (1 pt) 3. i. Ornithischian: The pubis of the Ornithischian group projects in a posterior direction or towards their tail. This is because their Pubis is parallel to the ischium. ii. Saurischian: The pubis of the Saurischian group projects in an anterior direction, or towards the front of their body. This is because their pubis points in the opposite direction of the ischium. 4. Click the hyperlinks and observe the orientation of the pubis within the pelvic girdle on the following dinosaur skeletons and indicate if the dinosaur most closely resembles a general saurischian or an ornithischian pelvic girdle. (5 pts) i. Tyrannosaurus – Saurischian pelvic girdle; the pubis faces towards an anterior direction. ii. Stegosaurus – Ornithischian pelvic girdle; the pubis faces towards a posterior direction. iii. Brachiosaurus - Saurischian pelvic girdle; the pubis faces towards an anterior direction. iv. Mussaurus - Saurischian pelvic girdle; the pubis faces towards an anterior direction. v. Triceratops - Saurischian pelvic girdle; the pubis faces towards an anterior direction. 4. Modern birds are “bird-hipped;” however, their ancestors (i.e. , the theropods) were “lizard-hipped.”  How does the pelvic girdle of the Graylag Goose ( Anser anser) differ from that of a basal theropod, such as  Herrerasaurus ?  (2 pts) The pelvic girdle of the Graylag Goose is an Ornithischian pelvis girdle. It has a pubis that faces the posterior most direction, or towards the tail; it is parallel to the ischium. However, the Herrerasaurus, has a Saurischian pelvis girdle. It has a pubis that faces the anterior most direction, or towards the front of their body; it points opposite of the ischium.
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