EARTH 7 Lecture Notes - Lecture 13: Tyrannosauridae, Evolution Of Birds, Troodontidae
11/14/17
● Tyrannosaurids
○ Appear to have originated in asia
○ Juvenile tyrannosaurid maybe have feathers?
○ Yutyrannus
■ Early cretaceous, liaoning, described in 2012
■ Large feathered tyrannosauroid
○ Likely that t-rex was somewhat feathered
● Maniraptors and Bird evolution
○Novelties that define maniraptors. Birds are maniraptors
○ Basal maniraptor diversity:
■Therizinosaurians, oviraptorosaurians, and more
○Dromaeosaurids and troodontids: complex feathers and other avian features
○Feathers and the link between development and evolution
○ An overview of early bird evolution, highlighting the iconic archaeopteryx
● Evolutionary novelties of Maniraptors = “hand-snatchers
1. Semi-lunate carpal
a. More wrist rotation
b. Initially helpful for manual dexterity, eventually becomes important for
flight!
2. Reverse pubis
a. Convergent in maniraptors and
ornithischians
● Therizinosaurians
○ Cretaceous
○ N america and Asia
■ 2 ft. claws
● herbivores
●Oviraptors = “egg snatchers”
○ Cretaceous of asia and N America
○ Egg incubators, not egg thieves
○ Most dont have teeth
■ Parental care
■ Bird-like brooding behavior
■ Warm-blooded
● Intermediate between crocodile and birds
○ Paired ovaries (like crocs. Birds only have one)
○ Laid eggs sequentially (like birds, which usually lay one
egg at a time. Crocs lay a bunch at once)
● Caudipteryx zoui
○ Another incredible specimen from liaoning (early
cretaceous)
○ One of several species of oviraptors with evidence of
multiple types of feathers.
○ Peacock sized
● Gigantoraptor
○ Late cretaceous of china
○ Described 2007
○ Much larger than most oviraptorosauria
Document Summary
Dromaeosaurids and troodontids : complex feathers and other avian features. Feathers and the link between development and evolution. An overview of early bird evolution , highlighting the iconic archaeopteryx: semi-lunate carpal. Evolutionary novelties of maniraptors = hand-snatchers: more wrist rotation b. Initially helpful for manual dexterity, eventually becomes important for flight: reverse pubis, convergent in maniraptors and ornithischians. Laid eggs sequentially (like birds, which usually lay one egg at a time. Another incredible specimen from liaoning (early cretaceous) One of several species of oviraptors with evidence of multiple types of feathers. Troodontids and dromaeosaurids have large, sickle claw on toe #2 (retractable) Evolutionary novelty of troodontids, dromaeosaurids, and avians (birds) Several groups with complex, asymmetrical feathers were not fliers (secondary loss?) Other potential aerodynamic uses (besides flight): stability, running, gliding, etc. Barbules keep all the barbs together to make a more solid aerodynamic surface. Late jurassic - end cretaceous; diverse and worldwide.
