ESS 100 Lecture Notes - Lecture 8: Dinosaur, Skull, Ornithischia

• School: UW
• Department: Earth and Space Sciences
• Course: ESS 100
• Professor: Ruth A.Martin

Document Summary

Pictures from lecture slides on class canvas website. Archosauria (ruling reptiles) is a major group of diapsida and is defined by single openings in each side of the skull in front of the eyes (antorbital fenestra) Compared to other diapsid groups have reduced number skull bones which lightens the skull and provides more room for muscles and other tissues. Primitive condition for all reptile clades is sharp pointed teeth. Another opening in the lower jaw: mandibular fenestra. High, narrow skull with a pointed snout. Fourth trochanter on femur: a large process on the shaft of femur that served as the attachment ppoint for major thigh retracting muscles. Two clades based on ankle joint arrangement: Peteinosaurus zambellii is smallest (wingspan 60 cm) and most primitive early. At least 3, but most commonly 5 fused vertebrae forming the sacrum. Expanded ilium or pelvic girdle to attach to the sacrum. Femur with angled ball joint to fit into acetabulum.