ZOO 2090 Lecture Notes - Lecture 15: Synapsid, Mesozoic, Amniote

• School: University of Guelph
• Department: Zoology
• Course: ZOO 2090
• Professor: Jinzhong Fu

Document Summary

Fossil mammals have distinct skeletal characteristics: middle ear malleus, incus, stapes, lower jaw only a single bone (dentary, jaw joint dentary and squamosal bones. The expansion of the dentary bone played a key role here: The establish of a second articulation released the functional constraints-- quadrate and articular are free to evolve! 7 cervical vertebrae, best at rotation: two condyles, best atlas-axis rotation this is a skeleton of an early mammal the vert is divided into distinct parts. also no ribs attached. 7 cervical vertebrae, best at rotation: two condyles, best atlas-axis rotation allows for easy rotation reduction of ribs - lumbar region allows for better motion of leg. 7 allows them to move quickly but also quietly most primitive form of walking (bears and people walk like this for ex) metatarsals tarsals horse. Morganucodontids are some of the best studied basal mammals. The morganucodontid megazostrodon (late triassic) was likely a small insectivore displaying agile, rapid movements and endothermy.