ZOO 2090 Lecture Notes - Lecture 13: Squamosal Bone, Xenarthra, Opossum

• School: University of Guelph
• Department: Zoology
• Course: ZOO 2090
• Professor: Fred Laberge

Document Summary

Objectives discuss the origin of mammals describe the characteristics of mammals and how they helped them succeed as a group. Important points the trends in synapsid evolution that led to mammals the characteristics of mammals. Synapsids: trend: pelycosaurs --> therapsids --> cynodonts --> mammals. Basal synapsids: pelycosaurs (extinct) ------ paraphyletic grouping late carboniferous dominant terrestrial carnivores: most, carniverous, but some herbivorous single temporal opening in cheek relatively dominant posterior position of the orbit, carnivorous pelycosaurs. Theraspids early permian, replaced pelycosaurs, dominant until end of triassic earliest theraspids displayed enlarged temporal fenestrae and reduction of palatal teeth: more terrestrial than pelycosaurs and displayed a greater diversity in body design, dinocephalians (extinct) Cynodont complex, diverse radiation of cynodonts marked by trend in size reduction largely replaced by terrestrial sauropsids in late triassic. Mammals arose from small cynodont ancestors early mammals were shrew-like animals, specialized ecological niches in jurassic and.